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1 .. Copyright (C) 2014-2018 Free Software Foundation, Inc.
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2 Originally contributed by David Malcolm <dmalcolm@redhat.com>
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3
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4 This is free software: you can redistribute it and/or modify it
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5 under the terms of the GNU General Public License as published by
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6 the Free Software Foundation, either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful, but
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10 WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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12 General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see
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16 <http://www.gnu.org/licenses/>.
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17
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18 .. default-domain:: c
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19
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20 Compiling a context
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21 ===================
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22
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23 Once populated, a :c:type:`gcc_jit_context *` can be compiled to
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24 machine code, either in-memory via :c:func:`gcc_jit_context_compile` or
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25 to disk via :c:func:`gcc_jit_context_compile_to_file`.
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26
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27 You can compile a context multiple times (using either form of
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28 compilation), although any errors that occur on the context will
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29 prevent any future compilation of that context.
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30
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31 In-memory compilation
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32 *********************
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33
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34 .. function:: gcc_jit_result *\
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35 gcc_jit_context_compile (gcc_jit_context *ctxt)
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36
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37 This calls into GCC and builds the code, returning a
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38 `gcc_jit_result *`.
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39
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40 If the result is non-NULL, the caller becomes responsible for
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41 calling :func:`gcc_jit_result_release` on it once they're done
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42 with it.
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43
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44 .. type:: gcc_jit_result
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45
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46 A `gcc_jit_result` encapsulates the result of compiling a context
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47 in-memory, and the lifetimes of any machine code functions or globals
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48 that are within the result.
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49
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50 .. function:: void *\
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51 gcc_jit_result_get_code (gcc_jit_result *result,\
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52 const char *funcname)
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53
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54 Locate a given function within the built machine code.
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55
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56 Functions are looked up by name. For this to succeed, a function
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57 with a name matching `funcname` must have been created on
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58 `result`'s context (or a parent context) via a call to
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59 :func:`gcc_jit_context_new_function` with `kind`
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60 :macro:`GCC_JIT_FUNCTION_EXPORTED`:
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61
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62 .. code-block:: c
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63
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64 gcc_jit_context_new_function (ctxt,
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65 any_location, /* or NULL */
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66 /* Required for func to be visible to
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67 gcc_jit_result_get_code: */
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68 GCC_JIT_FUNCTION_EXPORTED,
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69 any_return_type,
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70 /* Must string-compare equal: */
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71 funcname,
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72 /* etc */);
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73
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74 If such a function is not found (or `result` or `funcname` are
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75 ``NULL``), an error message will be emitted on stderr and
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76 ``NULL`` will be returned.
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77
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78 If the function is found, the result will need to be cast to a
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79 function pointer of the correct type before it can be called.
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80
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81 Note that the resulting machine code becomes invalid after
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82 :func:`gcc_jit_result_release` is called on the
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83 :type:`gcc_jit_result *`; attempting to call it after that may lead
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84 to a segmentation fault.
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85
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86 .. function:: void *\
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87 gcc_jit_result_get_global (gcc_jit_result *result,\
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88 const char *name)
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89
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90 Locate a given global within the built machine code.
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91
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92 Globals are looked up by name. For this to succeed, a global
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93 with a name matching `name` must have been created on
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94 `result`'s context (or a parent context) via a call to
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95 :func:`gcc_jit_context_new_global` with `kind`
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96 :macro:`GCC_JIT_GLOBAL_EXPORTED`.
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97
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98 If the global is found, the result will need to be cast to a
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99 pointer of the correct type before it can be called.
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100
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101 This is a *pointer* to the global, so e.g. for an :c:type:`int` this is
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102 an :c:type:`int *`.
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103
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104 For example, given an ``int foo;`` created this way:
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105
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106 .. code-block:: c
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107
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108 gcc_jit_lvalue *exported_global =
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109 gcc_jit_context_new_global (ctxt,
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110 any_location, /* or NULL */
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111 GCC_JIT_GLOBAL_EXPORTED,
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112 int_type,
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113 "foo");
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114
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115 we can access it like this:
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116
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117 .. code-block:: c
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118
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119 int *ptr_to_foo =
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120 (int *)gcc_jit_result_get_global (result, "foo");
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121
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122 If such a global is not found (or `result` or `name` are
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123 ``NULL``), an error message will be emitted on stderr and
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124 ``NULL`` will be returned.
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125
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126 Note that the resulting address becomes invalid after
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127 :func:`gcc_jit_result_release` is called on the
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128 :type:`gcc_jit_result *`; attempting to use it after that may lead
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129 to a segmentation fault.
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130
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131 .. function:: void\
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132 gcc_jit_result_release (gcc_jit_result *result)
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133
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134 Once we're done with the code, this unloads the built .so file.
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135 This cleans up the result; after calling this, it's no longer
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136 valid to use the result, or any code or globals that were obtained
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137 by calling :func:`gcc_jit_result_get_code` or
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138 :func:`gcc_jit_result_get_global` on it.
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139
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140
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141 Ahead-of-time compilation
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142 *************************
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143
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144 Although libgccjit is primarily aimed at just-in-time compilation, it
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145 can also be used for implementing more traditional ahead-of-time
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146 compilers, via the :c:func:`gcc_jit_context_compile_to_file`
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147 API entrypoint.
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148
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149 .. function:: void \
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150 gcc_jit_context_compile_to_file (gcc_jit_context *ctxt, \
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151 enum gcc_jit_output_kind output_kind,\
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152 const char *output_path)
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153
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154 Compile the :c:type:`gcc_jit_context *` to a file of the given
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155 kind.
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156
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157 :c:func:`gcc_jit_context_compile_to_file` ignores the suffix of
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158 ``output_path``, and insteads uses the given
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159 :c:type:`enum gcc_jit_output_kind` to decide what to do.
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160
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161 .. note::
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162
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163 This is different from the ``gcc`` program, which does make use of the
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164 suffix of the output file when determining what to do.
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165
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166 .. type:: enum gcc_jit_output_kind
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167
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168 The available kinds of output are:
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169
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170 ============================================== ==============
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171 Output kind Typical suffix
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172 ============================================== ==============
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173 :c:macro:`GCC_JIT_OUTPUT_KIND_ASSEMBLER` .s
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174 :c:macro:`GCC_JIT_OUTPUT_KIND_OBJECT_FILE` .o
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175 :c:macro:`GCC_JIT_OUTPUT_KIND_DYNAMIC_LIBRARY` .so or .dll
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176 :c:macro:`GCC_JIT_OUTPUT_KIND_EXECUTABLE` None, or .exe
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177 ============================================== ==============
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178
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179 .. c:macro:: GCC_JIT_OUTPUT_KIND_ASSEMBLER
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180
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181 Compile the context to an assembler file.
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182
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183 .. c:macro:: GCC_JIT_OUTPUT_KIND_OBJECT_FILE
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184
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185 Compile the context to an object file.
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186
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187 .. c:macro:: GCC_JIT_OUTPUT_KIND_DYNAMIC_LIBRARY
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188
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189 Compile the context to a dynamic library.
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190
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191 There is currently no support for specifying other libraries to link
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192 against.
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193
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194 .. c:macro:: GCC_JIT_OUTPUT_KIND_EXECUTABLE
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195
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196 Compile the context to an executable.
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197
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198 There is currently no support for specifying libraries to link
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199 against.
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