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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
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6 0. What is this.
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7
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8 This is a extension of C ( and a subset of C ). It has a
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9 programming unit which is called code segment. Code
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10 segment can be communicate with so called light weight continuation.
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11
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12
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13 #include <stdio.h>
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14
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15 code factorial(int n,int result,int orig,
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16 code(*print)(),code(*exit1)(), void *exit1env)
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17 {
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18 if (n<0) {
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19 printf("err %d!\n",n);
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20 goto (*exit1)(0),exit1env;
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21 }
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22 if (n==0)
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23 goto (*print)(n,result,orig,print,exit1,exit1env);
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24 else {
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25 result *= n;
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26 n--;
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27 goto factorial(n,result,orig,print,exit1,exit1env);
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28 }
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29 }
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30
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31 int main( int ac, char *av[])
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32 {
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33 int n;
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34 n = 10;
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35 goto factorial(n,1,n,print,return,environment);
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36 }
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37
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38 code print(int n,int result,int orig,code(*print)(),(*exit1)(),void*exit1env)
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39 {
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40 printf("%d! = %d\n",orig, result);
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41 goto (*exit1)(0),exit1env;
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42 }
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43
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44 If you don't use function call, this language becomes subset of C.
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45 It is called Continuation based C. Actually it can be a lower layer of
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46 C language. Normal C program can be compiled into CbC.
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47
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48 CbC is a kind of architecture independent assembler language.
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49
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50 1. Syntax
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51
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52 code code_segment_name(interfaces) {
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53 body;
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54 }
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55
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56 code is a type for code segment. A code segment has no return
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57 statements.
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58
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59 Interfaces are arguments. It can be struts. or unions. Some
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60 part of interfaces are mapped into registers. No
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61 references are allowed in register interface variables.
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62
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63 Goto statements transfer the control from a segment
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64 to a segment.
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65 goto segment_name(interfaces);
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66 If two code segments has a same interfaces, transfer cost is very
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67 small. It us usually a single jump instruction.
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68 If there are differences, some parallel assignment is performed.
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69
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70 2. Interaction between function and code segment.
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71
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72 In CwC, you can call C function at any time in code segments.
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73 If you want to call code segment from C and want to do some
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74 return, explicit handling of function environment.
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75
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76 goto factorial(n,1,n,print,return,environment);
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77
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78 return and environment is a special variable which contains
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79 return point. An environment variable is something like jumpbuf
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80 in setjump, but it is a simple pointer. Unlike jumpbuf,
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81 there is no way to allocate are for environment.
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82 void *environment;
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83
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84 A return variable is a continuation with environment of
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85 original function. It's type is varied for called function.
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86
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87 code (*return)(int return_value);
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88
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89 To go to the continuation, use goto with environment.
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90
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91 goto (*exit1)(0),exit1env;
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92
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93 3. How to use
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94
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95 mc-powerpc, mc-ia32 is a compiler. It generates assembler
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96 source code .s from C source code.
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97
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98 mc-powerpc source.c
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99 gcc source.s
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100 generates a.out.
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101 mc-powerpc source.c
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102 gcc -c sources.s
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103 generates sources.o
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104
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105 -s comments in assembler source.
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106 -c check only.
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107 -oname output file names
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245
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108 -Idir/ add library include directory. / is necessary
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192
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109
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110 Some examples can be fond in test directory.
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111
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112 3. Unimplemented lists
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113
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114 Mips version is not ready.
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115
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245
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116 64bit long long is now supported
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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 // Long long value (0LL) can be used but it gives long value.
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120 // Long is equal to an int and a pointer (32bit).
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192
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121
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122 Only Mac OS X and Red hat Linux is supported.
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123
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124 Inline directive is ignored and gives normal function definition.
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125
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245
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126 Register float is supported in Power PC
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127 // Register float arguments does no accepts assignment operation such as
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128 // *=, /=, +=.
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192
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129
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326
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130 //No built-in alloca.
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192
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131
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326
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132 // No varargs.
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133
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134 Use stdarg
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192
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135
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326
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136 // Switch statements is implemented as series of compare and branch,
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137 // no tables.
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192
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138
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326
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139 // Some operations such as concatenation are not implemented in macro
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140 // processor.
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192
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141
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142 Macro processor is a coroutine in this compiler, slightly different
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143 from cpp.
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144
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145 No -g support.
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146
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147 No runtime driver for CbC.
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148
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245
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149 // #include does not search, sources current directory.
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150 #include does search, sources current directory.
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192
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151
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339
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152 bit-field is supported, but no global initialization of bit-field.
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