CbC/CbC_llvm: tools/clang/docs/PCHInternals.rst annotate

annotate tools/clang/docs/PCHInternals.rst @ 3:9ad51c7bc036

1st commit. remove git dir and add all files.

author	Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date	Wed, 15 May 2013 06:43:32 +0900
parents
children	afa8332a0e37

rev	line source
3 9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	1 ========================================
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	2 Precompiled Header and Modules Internals
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	3 ========================================
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	4
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	5 .. contents::
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	6 :local:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	7
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	8 This document describes the design and implementation of Clang's precompiled
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	9 headers (PCH) and modules. If you are interested in the end-user view, please
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	10 see the :ref:`User's Manual <usersmanual-precompiled-headers>`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	11
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	12 Using Precompiled Headers with ``clang``
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	13 ----------------------------------------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	14
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	15 The Clang compiler frontend, ``clang -cc1``, supports two command line options
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	16 for generating and using PCH files.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	17
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	18 To generate PCH files using ``clang -cc1``, use the option :option:`-emit-pch`:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	19
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	20 .. code-block:: bash
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	21
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	22 $ clang -cc1 test.h -emit-pch -o test.h.pch
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	23
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	24 This option is transparently used by ``clang`` when generating PCH files. The
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	25 resulting PCH file contains the serialized form of the compiler's internal
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	26 representation after it has completed parsing and semantic analysis. The PCH
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	27 file can then be used as a prefix header with the :option:`-include-pch`
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	28 option:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	29
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	30 .. code-block:: bash
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	31
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	32 $ clang -cc1 -include-pch test.h.pch test.c -o test.s
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	33
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	34 Design Philosophy
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	35 -----------------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	36
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	37 Precompiled headers are meant to improve overall compile times for projects, so
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	38 the design of precompiled headers is entirely driven by performance concerns.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	39 The use case for precompiled headers is relatively simple: when there is a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	40 common set of headers that is included in nearly every source file in the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	41 project, we precompile that bundle of headers into a single precompiled
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	42 header (PCH file). Then, when compiling the source files in the project, we
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	43 load the PCH file first (as a prefix header), which acts as a stand-in for that
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	44 bundle of headers.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	45
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	46 A precompiled header implementation improves performance when:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	47
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	48 * Loading the PCH file is significantly faster than re-parsing the bundle of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	49 headers stored within the PCH file. Thus, a precompiled header design
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	50 attempts to minimize the cost of reading the PCH file. Ideally, this cost
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	51 should not vary with the size of the precompiled header file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	52
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	53 * The cost of generating the PCH file initially is not so large that it
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	54 counters the per-source-file performance improvement due to eliminating the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	55 need to parse the bundled headers in the first place. This is particularly
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	56 important on multi-core systems, because PCH file generation serializes the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	57 build when all compilations require the PCH file to be up-to-date.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	58
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	59 Modules, as implemented in Clang, use the same mechanisms as precompiled
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	60 headers to save a serialized AST file (one per module) and use those AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	61 modules. From an implementation standpoint, modules are a generalization of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	62 precompiled headers, lifting a number of restrictions placed on precompiled
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	63 headers. In particular, there can only be one precompiled header and it must
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	64 be included at the beginning of the translation unit. The extensions to the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	65 AST file format required for modules are discussed in the section on
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	66 :ref:`modules <pchinternals-modules>`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	67
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	68 Clang's AST files are designed with a compact on-disk representation, which
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	69 minimizes both creation time and the time required to initially load the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	70 file. The AST file itself contains a serialized representation of Clang's
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	71 abstract syntax trees and supporting data structures, stored using the same
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	72 compressed bitstream as `LLVM's bitcode file format
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	73 <http://llvm.org/docs/BitCodeFormat.html>`_.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	74
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	75 Clang's AST files are loaded "lazily" from disk. When an AST file is initially
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	76 loaded, Clang reads only a small amount of data from the AST file to establish
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	77 where certain important data structures are stored. The amount of data read in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	78 this initial load is independent of the size of the AST file, such that a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	79 larger AST file does not lead to longer AST load times. The actual header data
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	80 in the AST file --- macros, functions, variables, types, etc. --- is loaded
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	81 only when it is referenced from the user's code, at which point only that
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	82 entity (and those entities it depends on) are deserialized from the AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	83 With this approach, the cost of using an AST file for a translation unit is
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	84 proportional to the amount of code actually used from the AST file, rather than
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	85 being proportional to the size of the AST file itself.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	86
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	87 When given the :option:`-print-stats` option, Clang produces statistics
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	88 describing how much of the AST file was actually loaded from disk. For a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	89 simple "Hello, World!" program that includes the Apple ``Cocoa.h`` header
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	90 (which is built as a precompiled header), this option illustrates how little of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	91 the actual precompiled header is required:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	92
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	93 .. code-block:: none
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	94
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	95 *** AST File Statistics:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	96 895/39981 source location entries read (2.238563%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	97 19/15315 types read (0.124061%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	98 20/82685 declarations read (0.024188%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	99 154/58070 identifiers read (0.265197%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	100 0/7260 selectors read (0.000000%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	101 0/30842 statements read (0.000000%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	102 4/8400 macros read (0.047619%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	103 1/4995 lexical declcontexts read (0.020020%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	104 0/4413 visible declcontexts read (0.000000%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	105 0/7230 method pool entries read (0.000000%)
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	106 0 method pool misses
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	107
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	108 For this small program, only a tiny fraction of the source locations, types,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	109 declarations, identifiers, and macros were actually deserialized from the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	110 precompiled header. These statistics can be useful to determine whether the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	111 AST file implementation can be improved by making more of the implementation
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	112 lazy.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	113
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	114 Precompiled headers can be chained. When you create a PCH while including an
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	115 existing PCH, Clang can create the new PCH by referencing the original file and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	116 only writing the new data to the new file. For example, you could create a PCH
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	117 out of all the headers that are very commonly used throughout your project, and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	118 then create a PCH for every single source file in the project that includes the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	119 code that is specific to that file, so that recompiling the file itself is very
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	120 fast, without duplicating the data from the common headers for every file. The
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	121 mechanisms behind chained precompiled headers are discussed in a :ref:`later
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	122 section <pchinternals-chained>`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	123
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	124 AST File Contents
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	125 -----------------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	126
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	127 Clang's AST files are organized into several different blocks, each of which
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	128 contains the serialized representation of a part of Clang's internal
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	129 representation. Each of the blocks corresponds to either a block or a record
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	130 within `LLVM's bitstream format <http://llvm.org/docs/BitCodeFormat.html>`_.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	131 The contents of each of these logical blocks are described below.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	132
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	133 .. image:: PCHLayout.png
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	134
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	135 For a given AST file, the `llvm-bcanalyzer
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	136 <http://llvm.org/docs/CommandGuide/llvm-bcanalyzer.html>`_ utility can be used
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	137 to examine the actual structure of the bitstream for the AST file. This
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	138 information can be used both to help understand the structure of the AST file
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	139 and to isolate areas where AST files can still be optimized, e.g., through the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	140 introduction of abbreviations.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	141
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	142 Metadata Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	143 ^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	144
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	145 The metadata block contains several records that provide information about how
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	146 the AST file was built. This metadata is primarily used to validate the use of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	147 an AST file. For example, a precompiled header built for a 32-bit x86 target
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	148 cannot be used when compiling for a 64-bit x86 target. The metadata block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	149 contains information about:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	150
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	151 Language options
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	152 Describes the particular language dialect used to compile the AST file,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	153 including major options (e.g., Objective-C support) and more minor options
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	154 (e.g., support for "``//``" comments). The contents of this record correspond to
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	155 the ``LangOptions`` class.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	156
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	157 Target architecture
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	158 The target triple that describes the architecture, platform, and ABI for
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	159 which the AST file was generated, e.g., ``i386-apple-darwin9``.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	160
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	161 AST version
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	162 The major and minor version numbers of the AST file format. Changes in the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	163 minor version number should not affect backward compatibility, while changes
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	164 in the major version number imply that a newer compiler cannot read an older
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	165 precompiled header (and vice-versa).
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	166
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	167 Original file name
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	168 The full path of the header that was used to generate the AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	169
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	170 Predefines buffer
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	171 Although not explicitly stored as part of the metadata, the predefines buffer
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	172 is used in the validation of the AST file. The predefines buffer itself
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	173 contains code generated by the compiler to initialize the preprocessor state
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	174 according to the current target, platform, and command-line options. For
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	175 example, the predefines buffer will contain "``#define __STDC__ 1``" when we
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	176 are compiling C without Microsoft extensions. The predefines buffer itself
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	177 is stored within the :ref:`pchinternals-sourcemgr`, but its contents are
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	178 verified along with the rest of the metadata.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	179
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	180 A chained PCH file (that is, one that references another PCH) and a module
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	181 (which may import other modules) have additional metadata containing the list
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	182 of all AST files that this AST file depends on. Each of those files will be
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	183 loaded along with this AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	184
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	185 For chained precompiled headers, the language options, target architecture and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	186 predefines buffer data is taken from the end of the chain, since they have to
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	187 match anyway.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	188
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	189 .. _pchinternals-sourcemgr:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	190
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	191 Source Manager Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	192 ^^^^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	193
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	194 The source manager block contains the serialized representation of Clang's
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	195 :ref:`SourceManager <SourceManager>` class, which handles the mapping from
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	196 source locations (as represented in Clang's abstract syntax tree) into actual
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	197 column/line positions within a source file or macro instantiation. The AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	198 file's representation of the source manager also includes information about all
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	199 of the headers that were (transitively) included when building the AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	200
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	201 The bulk of the source manager block is dedicated to information about the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	202 various files, buffers, and macro instantiations into which a source location
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	203 can refer. Each of these is referenced by a numeric "file ID", which is a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	204 unique number (allocated starting at 1) stored in the source location. Clang
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	205 serializes the information for each kind of file ID, along with an index that
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	206 maps file IDs to the position within the AST file where the information about
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	207 that file ID is stored. The data associated with a file ID is loaded only when
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	208 required by the front end, e.g., to emit a diagnostic that includes a macro
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	209 instantiation history inside the header itself.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	210
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	211 The source manager block also contains information about all of the headers
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	212 that were included when building the AST file. This includes information about
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	213 the controlling macro for the header (e.g., when the preprocessor identified
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	214 that the contents of the header dependent on a macro like
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	215 ``LLVM_CLANG_SOURCEMANAGER_H``).
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	216
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	217 .. _pchinternals-preprocessor:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	218
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	219 Preprocessor Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	220 ^^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	221
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	222 The preprocessor block contains the serialized representation of the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	223 preprocessor. Specifically, it contains all of the macros that have been
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	224 defined by the end of the header used to build the AST file, along with the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	225 token sequences that comprise each macro. The macro definitions are only read
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	226 from the AST file when the name of the macro first occurs in the program. This
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	227 lazy loading of macro definitions is triggered by lookups into the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	228 :ref:`identifier table <pchinternals-ident-table>`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	229
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	230 .. _pchinternals-types:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	231
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	232 Types Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	233 ^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	234
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	235 The types block contains the serialized representation of all of the types
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	236 referenced in the translation unit. Each Clang type node (``PointerType``,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	237 ``FunctionProtoType``, etc.) has a corresponding record type in the AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	238 When types are deserialized from the AST file, the data within the record is
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	239 used to reconstruct the appropriate type node using the AST context.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	240
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	241 Each type has a unique type ID, which is an integer that uniquely identifies
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	242 that type. Type ID 0 represents the NULL type, type IDs less than
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	243 ``NUM_PREDEF_TYPE_IDS`` represent predefined types (``void``, ``float``, etc.),
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	244 while other "user-defined" type IDs are assigned consecutively from
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	245 ``NUM_PREDEF_TYPE_IDS`` upward as the types are encountered. The AST file has
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	246 an associated mapping from the user-defined types block to the location within
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	247 the types block where the serialized representation of that type resides,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	248 enabling lazy deserialization of types. When a type is referenced from within
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	249 the AST file, that reference is encoded using the type ID shifted left by 3
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	250 bits. The lower three bits are used to represent the ``const``, ``volatile``,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	251 and ``restrict`` qualifiers, as in Clang's :ref:`QualType <QualType>` class.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	252
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	253 .. _pchinternals-decls:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	254
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	255 Declarations Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	256 ^^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	257
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	258 The declarations block contains the serialized representation of all of the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	259 declarations referenced in the translation unit. Each Clang declaration node
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	260 (``VarDecl``, ``FunctionDecl``, etc.) has a corresponding record type in the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	261 AST file. When declarations are deserialized from the AST file, the data
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	262 within the record is used to build and populate a new instance of the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	263 corresponding ``Decl`` node. As with types, each declaration node has a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	264 numeric ID that is used to refer to that declaration within the AST file. In
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	265 addition, a lookup table provides a mapping from that numeric ID to the offset
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	266 within the precompiled header where that declaration is described.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	267
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	268 Declarations in Clang's abstract syntax trees are stored hierarchically. At
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	269 the top of the hierarchy is the translation unit (``TranslationUnitDecl``),
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	270 which contains all of the declarations in the translation unit but is not
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	271 actually written as a specific declaration node. Its child declarations (such
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	272 as functions or struct types) may also contain other declarations inside them,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	273 and so on. Within Clang, each declaration is stored within a :ref:`declaration
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	274 context <DeclContext>`, as represented by the ``DeclContext`` class.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	275 Declaration contexts provide the mechanism to perform name lookup within a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	276 given declaration (e.g., find the member named ``x`` in a structure) and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	277 iterate over the declarations stored within a context (e.g., iterate over all
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	278 of the fields of a structure for structure layout).
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	279
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	280 In Clang's AST file format, deserializing a declaration that is a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	281 ``DeclContext`` is a separate operation from deserializing all of the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	282 declarations stored within that declaration context. Therefore, Clang will
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	283 deserialize the translation unit declaration without deserializing the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	284 declarations within that translation unit. When required, the declarations
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	285 stored within a declaration context will be deserialized. There are two
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	286 representations of the declarations within a declaration context, which
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	287 correspond to the name-lookup and iteration behavior described above:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	288
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	289 * When the front end performs name lookup to find a name ``x`` within a given
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	290 declaration context (for example, during semantic analysis of the expression
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	291 ``p->x``, where ``p``'s type is defined in the precompiled header), Clang
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	292 refers to an on-disk hash table that maps from the names within that
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	293 declaration context to the declaration IDs that represent each visible
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	294 declaration with that name. The actual declarations will then be
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	295 deserialized to provide the results of name lookup.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	296 * When the front end performs iteration over all of the declarations within a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	297 declaration context, all of those declarations are immediately
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	298 de-serialized. For large declaration contexts (e.g., the translation unit),
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	299 this operation is expensive; however, large declaration contexts are not
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	300 traversed in normal compilation, since such a traversal is unnecessary.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	301 However, it is common for the code generator and semantic analysis to
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	302 traverse declaration contexts for structs, classes, unions, and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	303 enumerations, although those contexts contain relatively few declarations in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	304 the common case.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	305
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	306 Statements and Expressions
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	307 ^^^^^^^^^^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	308
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	309 Statements and expressions are stored in the AST file in both the :ref:`types
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	310 <pchinternals-types>` and the :ref:`declarations <pchinternals-decls>` blocks,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	311 because every statement or expression will be associated with either a type or
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	312 declaration. The actual statement and expression records are stored
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	313 immediately following the declaration or type that owns the statement or
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	314 expression. For example, the statement representing the body of a function
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	315 will be stored directly following the declaration of the function.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	316
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	317 As with types and declarations, each statement and expression kind in Clang's
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	318 abstract syntax tree (``ForStmt``, ``CallExpr``, etc.) has a corresponding
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	319 record type in the AST file, which contains the serialized representation of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	320 that statement or expression. Each substatement or subexpression within an
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	321 expression is stored as a separate record (which keeps most records to a fixed
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	322 size). Within the AST file, the subexpressions of an expression are stored, in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	323 reverse order, prior to the expression that owns those expression, using a form
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	324 of `Reverse Polish Notation
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	325 <http://en.wikipedia.org/wiki/Reverse_Polish_notation>`_. For example, an
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	326 expression ``3 - 4 + 5`` would be represented as follows:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	327
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	328 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	329 \| ``IntegerLiteral(5)`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	330 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	331 \| ``IntegerLiteral(4)`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	332 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	333 \| ``IntegerLiteral(3)`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	334 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	335 \| ``IntegerLiteral(-)`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	336 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	337 \| ``IntegerLiteral(+)`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	338 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	339 \| ``STOP`` \|
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	340 +-----------------------+
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	341
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	342 When reading this representation, Clang evaluates each expression record it
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	343 encounters, builds the appropriate abstract syntax tree node, and then pushes
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	344 that expression on to a stack. When a record contains N subexpressions ---
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	345 ``BinaryOperator`` has two of them --- those expressions are popped from the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	346 top of the stack. The special STOP code indicates that we have reached the end
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	347 of a serialized expression or statement; other expression or statement records
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	348 may follow, but they are part of a different expression.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	349
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	350 .. _pchinternals-ident-table:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	351
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	352 Identifier Table Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	353 ^^^^^^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	354
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	355 The identifier table block contains an on-disk hash table that maps each
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	356 identifier mentioned within the AST file to the serialized representation of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	357 the identifier's information (e.g, the ``IdentifierInfo`` structure). The
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	358 serialized representation contains:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	359
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	360 * The actual identifier string.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	361 * Flags that describe whether this identifier is the name of a built-in, a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	362 poisoned identifier, an extension token, or a macro.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	363 * If the identifier names a macro, the offset of the macro definition within
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	364 the :ref:`pchinternals-preprocessor`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	365 * If the identifier names one or more declarations visible from translation
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	366 unit scope, the :ref:`declaration IDs <pchinternals-decls>` of these
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	367 declarations.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	368
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	369 When an AST file is loaded, the AST file reader mechanism introduces itself
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	370 into the identifier table as an external lookup source. Thus, when the user
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	371 program refers to an identifier that has not yet been seen, Clang will perform
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	372 a lookup into the identifier table. If an identifier is found, its contents
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	373 (macro definitions, flags, top-level declarations, etc.) will be deserialized,
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	374 at which point the corresponding ``IdentifierInfo`` structure will have the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	375 same contents it would have after parsing the headers in the AST file.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	376
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	377 Within the AST file, the identifiers used to name declarations are represented
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	378 with an integral value. A separate table provides a mapping from this integral
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	379 value (the identifier ID) to the location within the on-disk hash table where
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	380 that identifier is stored. This mapping is used when deserializing the name of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	381 a declaration, the identifier of a token, or any other construct in the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	382 file that refers to a name.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	383
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	384 .. _pchinternals-method-pool:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	385
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	386 Method Pool Block
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	387 ^^^^^^^^^^^^^^^^^
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	388
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	389 The method pool block is represented as an on-disk hash table that serves two
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	390 purposes: it provides a mapping from the names of Objective-C selectors to the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	391 set of Objective-C instance and class methods that have that particular
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	392 selector (which is required for semantic analysis in Objective-C) and also
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	393 stores all of the selectors used by entities within the AST file. The design
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	394 of the method pool is similar to that of the :ref:`identifier table
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	395 <pchinternals-ident-table>`: the first time a particular selector is formed
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	396 during the compilation of the program, Clang will search in the on-disk hash
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	397 table of selectors; if found, Clang will read the Objective-C methods
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	398 associated with that selector into the appropriate front-end data structure
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	399 (``Sema::InstanceMethodPool`` and ``Sema::FactoryMethodPool`` for instance and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	400 class methods, respectively).
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	401
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	402 As with identifiers, selectors are represented by numeric values within the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	403 file. A separate index maps these numeric selector values to the offset of the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	404 selector within the on-disk hash table, and will be used when de-serializing an
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	405 Objective-C method declaration (or other Objective-C construct) that refers to
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	406 the selector.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	407
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	408 AST Reader Integration Points
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	409 -----------------------------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	410
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	411 The "lazy" deserialization behavior of AST files requires their integration
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	412 into several completely different submodules of Clang. For example, lazily
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	413 deserializing the declarations during name lookup requires that the name-lookup
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	414 routines be able to query the AST file to find entities stored there.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	415
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	416 For each Clang data structure that requires direct interaction with the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	417 reader logic, there is an abstract class that provides the interface between
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	418 the two modules. The ``ASTReader`` class, which handles the loading of an AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	419 file, inherits from all of these abstract classes to provide lazy
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	420 deserialization of Clang's data structures. ``ASTReader`` implements the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	421 following abstract classes:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	422
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	423 ``ExternalSLocEntrySource``
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	424 This abstract interface is associated with the ``SourceManager`` class, and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	425 is used whenever the :ref:`source manager <pchinternals-sourcemgr>` needs to
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	426 load the details of a file, buffer, or macro instantiation.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	427
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	428 ``IdentifierInfoLookup``
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	429 This abstract interface is associated with the ``IdentifierTable`` class, and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	430 is used whenever the program source refers to an identifier that has not yet
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	431 been seen. In this case, the AST reader searches for this identifier within
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	432 its :ref:`identifier table <pchinternals-ident-table>` to load any top-level
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	433 declarations or macros associated with that identifier.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	434
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	435 ``ExternalASTSource``
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	436 This abstract interface is associated with the ``ASTContext`` class, and is
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	437 used whenever the abstract syntax tree nodes need to loaded from the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	438 file. It provides the ability to de-serialize declarations and types
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	439 identified by their numeric values, read the bodies of functions when
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	440 required, and read the declarations stored within a declaration context
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	441 (either for iteration or for name lookup).
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	442
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	443 ``ExternalSemaSource``
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	444 This abstract interface is associated with the ``Sema`` class, and is used
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	445 whenever semantic analysis needs to read information from the :ref:`global
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	446 method pool <pchinternals-method-pool>`.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	447
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	448 .. _pchinternals-chained:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	449
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	450 Chained precompiled headers
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	451 ---------------------------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	452
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	453 Chained precompiled headers were initially intended to improve the performance
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	454 of IDE-centric operations such as syntax highlighting and code completion while
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	455 a particular source file is being edited by the user. To minimize the amount
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	456 of reparsing required after a change to the file, a form of precompiled header
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	457 --- called a precompiled preamble --- is automatically generated by parsing
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	458 all of the headers in the source file, up to and including the last
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	459 ``#include``. When only the source file changes (and none of the headers it
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	460 depends on), reparsing of that source file can use the precompiled preamble and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	461 start parsing after the ``#include``\ s, so parsing time is proportional to the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	462 size of the source file (rather than all of its includes). However, the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	463 compilation of that translation unit may already use a precompiled header: in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	464 this case, Clang will create the precompiled preamble as a chained precompiled
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	465 header that refers to the original precompiled header. This drastically
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	466 reduces the time needed to serialize the precompiled preamble for use in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	467 reparsing.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	468
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	469 Chained precompiled headers get their name because each precompiled header can
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	470 depend on one other precompiled header, forming a chain of dependencies. A
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	471 translation unit will then include the precompiled header that starts the chain
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	472 (i.e., nothing depends on it). This linearity of dependencies is important for
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	473 the semantic model of chained precompiled headers, because the most-recent
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	474 precompiled header can provide information that overrides the information
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	475 provided by the precompiled headers it depends on, just like a header file
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	476 ``B.h`` that includes another header ``A.h`` can modify the state produced by
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	477 parsing ``A.h``, e.g., by ``#undef``'ing a macro defined in ``A.h``.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	478
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	479 There are several ways in which chained precompiled headers generalize the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	480 file model:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	481
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	482 Numbering of IDs
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	483 Many different kinds of entities --- identifiers, declarations, types, etc.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	484 --- have ID numbers that start at 1 or some other predefined constant and
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	485 grow upward. Each precompiled header records the maximum ID number it has
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	486 assigned in each category. Then, when a new precompiled header is generated
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	487 that depends on (chains to) another precompiled header, it will start
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	488 counting at the next available ID number. This way, one can determine, given
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	489 an ID number, which AST file actually contains the entity.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	490
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	491 Name lookup
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	492 When writing a chained precompiled header, Clang attempts to write only
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	493 information that has changed from the precompiled header on which it is
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	494 based. This changes the lookup algorithm for the various tables, such as the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	495 :ref:`identifier table <pchinternals-ident-table>`: the search starts at the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	496 most-recent precompiled header. If no entry is found, lookup then proceeds
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	497 to the identifier table in the precompiled header it depends on, and so one.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	498 Once a lookup succeeds, that result is considered definitive, overriding any
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	499 results from earlier precompiled headers.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	500
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	501 Update records
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	502 There are various ways in which a later precompiled header can modify the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	503 entities described in an earlier precompiled header. For example, later
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	504 precompiled headers can add entries into the various name-lookup tables for
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	505 the translation unit or namespaces, or add new categories to an Objective-C
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	506 class. Each of these updates is captured in an "update record" that is
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	507 stored in the chained precompiled header file and will be loaded along with
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	508 the original entity.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	509
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	510 .. _pchinternals-modules:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	511
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	512 Modules
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	513 -------
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	514
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	515 Modules generalize the chained precompiled header model yet further, from a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	516 linear chain of precompiled headers to an arbitrary directed acyclic graph
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	517 (DAG) of AST files. All of the same techniques used to make chained
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	518 precompiled headers work --- ID number, name lookup, update records --- are
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	519 shared with modules. However, the DAG nature of modules introduce a number of
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	520 additional complications to the model:
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	521
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	522 Numbering of IDs
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	523 The simple, linear numbering scheme used in chained precompiled headers falls
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	524 apart with the module DAG, because different modules may end up with
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	525 different numbering schemes for entities they imported from common shared
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	526 modules. To account for this, each module file provides information about
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	527 which modules it depends on and which ID numbers it assigned to the entities
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	528 in those modules, as well as which ID numbers it took for its own new
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	529 entities. The AST reader then maps these "local" ID numbers into a "global"
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	530 ID number space for the current translation unit, providing a 1-1 mapping
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	531 between entities (in whatever AST file they inhabit) and global ID numbers.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	532 If that translation unit is then serialized into an AST file, this mapping
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	533 will be stored for use when the AST file is imported.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	534
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	535 Declaration merging
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	536 It is possible for a given entity (from the language's perspective) to be
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	537 declared multiple times in different places. For example, two different
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	538 headers can have the declaration of ``printf`` or could forward-declare
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	539 ``struct stat``. If each of those headers is included in a module, and some
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	540 third party imports both of those modules, there is a potentially serious
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	541 problem: name lookup for ``printf`` or ``struct stat`` will find both
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	542 declarations, but the AST nodes are unrelated. This would result in a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	543 compilation error, due to an ambiguity in name lookup. Therefore, the AST
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	544 reader performs declaration merging according to the appropriate language
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	545 semantics, ensuring that the two disjoint declarations are merged into a
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	546 single redeclaration chain (with a common canonical declaration), so that it
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	547 is as if one of the headers had been included before the other.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	548
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	549 Name Visibility
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	550 Modules allow certain names that occur during module creation to be "hidden",
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	551 so that they are not part of the public interface of the module and are not
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	552 visible to its clients. The AST reader maintains a "visible" bit on various
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	553 AST nodes (declarations, macros, etc.) to indicate whether that particular
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	554 AST node is currently visible; the various name lookup mechanisms in Clang
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	555 inspect the visible bit to determine whether that entity, which is still in
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	556 the AST (because other, visible AST nodes may depend on it), can actually be
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	557 found by name lookup. When a new (sub)module is imported, it may make
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	558 existing, non-visible, already-deserialized AST nodes visible; it is the
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	559 responsibility of the AST reader to find and update these AST nodes when it
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	560 is notified of the import.
9ad51c7bc036 1st commit. remove git dir and add all files. Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> parents: diff changeset	561

Mercurial > hg > CbC > CbC_llvm

annotate tools/clang/docs/PCHInternals.rst @ 3:9ad51c7bc036