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192
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1 C with Continuation (CwC) and Continuation based C (CbC)
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2 $Id$
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3 Shinji Kono
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4 University of the Ryukyus
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5 2003 December
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6
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7 0. What is this.
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8
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9 This is a extension of C ( and a subset of C ). It has a
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10 programming unit which is called code segment. Code
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11 segment can be communicate with so called light weight continuation.
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12
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13
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14 #include <stdio.h>
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15
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16 code factorial(int n,int result,int orig,
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17 code(*print)(),code(*exit1)(), void *exit1env)
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18 {
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19 if (n<0) {
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20 printf("err %d!\n",n);
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21 goto (*exit1)(0),exit1env;
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22 }
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23 if (n==0)
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24 goto (*print)(n,result,orig,print,exit1,exit1env);
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25 else {
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26 result *= n;
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27 n--;
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28 goto factorial(n,result,orig,print,exit1,exit1env);
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29 }
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30 }
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31
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32 int main( int ac, char *av[])
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33 {
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34 int n;
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35 n = 10;
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36 goto factorial(n,1,n,print,return,environment);
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37 }
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38
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39 code print(int n,int result,int orig,code(*print)(),(*exit1)(),void*exit1env)
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40 {
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41 printf("%d! = %d\n",orig, result);
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42 goto (*exit1)(0),exit1env;
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43 }
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44
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45 If you don't use function call, this language becomes subset of C.
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46 It is called Continuation based C. Actually it can be a lower layer of
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47 C language. Normal C program can be compiled into CbC.
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48
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49 CbC is a kind of architecture independent assembler language.
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50
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51 1. Syntax
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52
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53 code code_segment_name(interfaces) {
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54 body;
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55 }
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56
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57 code is a type for code segment. A code segment has no return
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58 statements.
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59
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60 Interfaces are arguments. It can be struts. or unions. Some
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61 part of interfaces are mapped into registers. No
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62 references are allowed in register interface variables.
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63
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64 Goto statements transfer the control from a segment
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65 to a segment.
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66 goto segment_name(interfaces);
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67 If two code segments has a same interfaces, transfer cost is very
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68 small. It us usually a single jump instruction.
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69 If there are differences, some parallel assignment is performed.
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70
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71 2. Interaction between function and code segment.
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72
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73 In CwC, you can call C function at any time in code segments.
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74 If you want to call code segment from C and want to do some
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75 return, explicit handling of function environment.
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76
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77 goto factorial(n,1,n,print,return,environment);
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78
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79 return and environment is a special variable which contains
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80 return point. An environment variable is something like jumpbuf
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81 in setjump, but it is a simple pointer. Unlike jumpbuf,
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82 there is no way to allocate are for environment.
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83 void *environment;
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84
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85 A return variable is a continuation with environment of
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86 original function. It's type is varied for called function.
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87
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88 code (*return)(int return_value);
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89
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90 To go to the continuation, use goto with environment.
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91
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92 goto (*exit1)(0),exit1env;
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93
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94 3. How to use
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95
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96 mc-powerpc, mc-ia32 is a compiler. It generates assembler
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97 source code .s from C source code.
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98
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99 mc-powerpc source.c
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100 gcc source.s
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101 generates a.out.
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102 mc-powerpc source.c
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103 gcc -c sources.s
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104 generates sources.o
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105
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106 -s comments in assembler source.
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107 -c check only.
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108 -oname output file names
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109 -Idir add library include directory
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110
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111 Some examples can be fond in test directory.
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112
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113 3. Unimplemented lists
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114
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115 Mips version is not ready.
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116
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117 long long, long double, unsigned long long can be used as type,
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118 but no operation (including assignment) are no allowed.
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119
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120 Long long value (0LL) can be used but it gives long value.
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121 Long is equal to an int and a pointer (32bit).
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122
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123 Only Mac OS X and Red hat Linux is supported.
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124
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125 Inline directive is ignored and gives normal function definition.
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126
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127 Register float arguments does no accepts assignment operation such as
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128 *=, /=, +=.
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129
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130 No built-in alloca.
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131
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132 No varargs.
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133
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134 Switch statements is implemented as series of compare and branch,
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135 no tables.
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136
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137 Some operations such as concatenation are not implemented in macro
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138 processor.
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139
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140 Macro processor is a coroutine in this compiler, slightly different
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141 from cpp.
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142
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143 No -g support.
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144
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145 No runtime driver for CbC.
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146
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147 #include does not search, sources current directory.
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148
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149
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