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Copies published by the Free Software Foundation raise funds for GNU development. --> <!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ --> <head> <title>Macros for Initialization (GNU Compiler Collection (GCC) Internals)</title> <meta name="description" content="Macros for Initialization (GNU Compiler Collection (GCC) Internals)"> <meta name="keywords" content="Macros for Initialization (GNU Compiler Collection (GCC) Internals)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <link href="index.html#Top" rel="start" title="Top"> <link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="Assembler-Format.html#Assembler-Format" rel="up" title="Assembler Format"> <link href="Instruction-Output.html#Instruction-Output" rel="next" title="Instruction Output"> <link href="Initialization.html#Initialization" rel="prev" title="Initialization"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} div.smalllisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} pre.smalldisplay {font-family: inherit; font-size: smaller} pre.smallexample {font-size: smaller} pre.smallformat {font-family: inherit; font-size: smaller} pre.smalllisp {font-size: smaller} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <a name="Macros-for-Initialization"></a> <div class="header"> <p> Next: <a href="Instruction-Output.html#Instruction-Output" accesskey="n" rel="next">Instruction Output</a>, Previous: <a href="Initialization.html#Initialization" accesskey="p" rel="prev">Initialization</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> </div> <hr> <a name="Macros-Controlling-Initialization-Routines"></a> <h4 class="subsection">18.20.6 Macros Controlling Initialization Routines</h4> <p>Here are the macros that control how the compiler handles initialization and termination functions: </p> <dl> <dt><a name="index-INIT_005fSECTION_005fASM_005fOP-1"></a>Macro: <strong>INIT_SECTION_ASM_OP</strong></dt> <dd><p>If defined, a C string constant, including spacing, for the assembler operation to identify the following data as initialization code. If not defined, GCC will assume such a section does not exist. When you are using special sections for initialization and termination functions, this macro also controls how <samp>crtstuff.c</samp> and <samp>libgcc2.c</samp> arrange to run the initialization functions. </p></dd></dl> <dl> <dt><a name="index-HAS_005fINIT_005fSECTION"></a>Macro: <strong>HAS_INIT_SECTION</strong></dt> <dd><p>If defined, <code>main</code> will not call <code>__main</code> as described above. This macro should be defined for systems that control start-up code on a symbol-by-symbol basis, such as OSF/1, and should not be defined explicitly for systems that support <code>INIT_SECTION_ASM_OP</code>. </p></dd></dl> <dl> <dt><a name="index-LD_005fINIT_005fSWITCH"></a>Macro: <strong>LD_INIT_SWITCH</strong></dt> <dd><p>If defined, a C string constant for a switch that tells the linker that the following symbol is an initialization routine. </p></dd></dl> <dl> <dt><a name="index-LD_005fFINI_005fSWITCH"></a>Macro: <strong>LD_FINI_SWITCH</strong></dt> <dd><p>If defined, a C string constant for a switch that tells the linker that the following symbol is a finalization routine. </p></dd></dl> <dl> <dt><a name="index-COLLECT_005fSHARED_005fINIT_005fFUNC"></a>Macro: <strong>COLLECT_SHARED_INIT_FUNC</strong> <em>(<var>stream</var>, <var>func</var>)</em></dt> <dd><p>If defined, a C statement that will write a function that can be automatically called when a shared library is loaded. The function should call <var>func</var>, which takes no arguments. If not defined, and the object format requires an explicit initialization function, then a function called <code>_GLOBAL__DI</code> will be generated. </p> <p>This function and the following one are used by collect2 when linking a shared library that needs constructors or destructors, or has DWARF2 exception tables embedded in the code. </p></dd></dl> <dl> <dt><a name="index-COLLECT_005fSHARED_005fFINI_005fFUNC"></a>Macro: <strong>COLLECT_SHARED_FINI_FUNC</strong> <em>(<var>stream</var>, <var>func</var>)</em></dt> <dd><p>If defined, a C statement that will write a function that can be automatically called when a shared library is unloaded. The function should call <var>func</var>, which takes no arguments. If not defined, and the object format requires an explicit finalization function, then a function called <code>_GLOBAL__DD</code> will be generated. </p></dd></dl> <dl> <dt><a name="index-INVOKE_005f_005fmain"></a>Macro: <strong>INVOKE__main</strong></dt> <dd><p>If defined, <code>main</code> will call <code>__main</code> despite the presence of <code>INIT_SECTION_ASM_OP</code>. This macro should be defined for systems where the init section is not actually run automatically, but is still useful for collecting the lists of constructors and destructors. </p></dd></dl> <dl> <dt><a name="index-SUPPORTS_005fINIT_005fPRIORITY"></a>Macro: <strong>SUPPORTS_INIT_PRIORITY</strong></dt> <dd><p>If nonzero, the C++ <code>init_priority</code> attribute is supported and the compiler should emit instructions to control the order of initialization of objects. If zero, the compiler will issue an error message upon encountering an <code>init_priority</code> attribute. </p></dd></dl> <dl> <dt><a name="index-TARGET_005fHAVE_005fCTORS_005fDTORS"></a>Target Hook: <em>bool</em> <strong>TARGET_HAVE_CTORS_DTORS</strong></dt> <dd><p>This value is true if the target supports some “native” method of collecting constructors and destructors to be run at startup and exit. It is false if we must use <code>collect2</code>. </p></dd></dl> <dl> <dt><a name="index-TARGET_005fASM_005fCONSTRUCTOR"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_CONSTRUCTOR</strong> <em>(rtx <var>symbol</var>, int <var>priority</var>)</em></dt> <dd><p>If defined, a function that outputs assembler code to arrange to call the function referenced by <var>symbol</var> at initialization time. </p> <p>Assume that <var>symbol</var> is a <code>SYMBOL_REF</code> for a function taking no arguments and with no return value. If the target supports initialization priorities, <var>priority</var> is a value between 0 and <code>MAX_INIT_PRIORITY</code>; otherwise it must be <code>DEFAULT_INIT_PRIORITY</code>. </p> <p>If this macro is not defined by the target, a suitable default will be chosen if (1) the target supports arbitrary section names, (2) the target defines <code>CTORS_SECTION_ASM_OP</code>, or (3) <code>USE_COLLECT2</code> is not defined. </p></dd></dl> <dl> <dt><a name="index-TARGET_005fASM_005fDESTRUCTOR"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_DESTRUCTOR</strong> <em>(rtx <var>symbol</var>, int <var>priority</var>)</em></dt> <dd><p>This is like <code>TARGET_ASM_CONSTRUCTOR</code> but used for termination functions rather than initialization functions. </p></dd></dl> <p>If <code>TARGET_HAVE_CTORS_DTORS</code> is true, the initialization routine generated for the generated object file will have static linkage. </p> <p>If your system uses <code>collect2</code> as the means of processing constructors, then that program normally uses <code>nm</code> to scan an object file for constructor functions to be called. </p> <p>On certain kinds of systems, you can define this macro to make <code>collect2</code> work faster (and, in some cases, make it work at all): </p> <dl> <dt><a name="index-OBJECT_005fFORMAT_005fCOFF"></a>Macro: <strong>OBJECT_FORMAT_COFF</strong></dt> <dd><p>Define this macro if the system uses COFF (Common Object File Format) object files, so that <code>collect2</code> can assume this format and scan object files directly for dynamic constructor/destructor functions. </p> <p>This macro is effective only in a native compiler; <code>collect2</code> as part of a cross compiler always uses <code>nm</code> for the target machine. </p></dd></dl> <dl> <dt><a name="index-REAL_005fNM_005fFILE_005fNAME"></a>Macro: <strong>REAL_NM_FILE_NAME</strong></dt> <dd><p>Define this macro as a C string constant containing the file name to use to execute <code>nm</code>. The default is to search the path normally for <code>nm</code>. </p></dd></dl> <dl> <dt><a name="index-NM_005fFLAGS"></a>Macro: <strong>NM_FLAGS</strong></dt> <dd><p><code>collect2</code> calls <code>nm</code> to scan object files for static constructors and destructors and LTO info. By default, <samp>-n</samp> is passed. Define <code>NM_FLAGS</code> to a C string constant if other options are needed to get the same output format as GNU <code>nm -n</code> produces. </p></dd></dl> <p>If your system supports shared libraries and has a program to list the dynamic dependencies of a given library or executable, you can define these macros to enable support for running initialization and termination functions in shared libraries: </p> <dl> <dt><a name="index-LDD_005fSUFFIX"></a>Macro: <strong>LDD_SUFFIX</strong></dt> <dd><p>Define this macro to a C string constant containing the name of the program which lists dynamic dependencies, like <code>ldd</code> under SunOS 4. </p></dd></dl> <dl> <dt><a name="index-PARSE_005fLDD_005fOUTPUT"></a>Macro: <strong>PARSE_LDD_OUTPUT</strong> <em>(<var>ptr</var>)</em></dt> <dd><p>Define this macro to be C code that extracts filenames from the output of the program denoted by <code>LDD_SUFFIX</code>. <var>ptr</var> is a variable of type <code>char *</code> that points to the beginning of a line of output from <code>LDD_SUFFIX</code>. If the line lists a dynamic dependency, the code must advance <var>ptr</var> to the beginning of the filename on that line. Otherwise, it must set <var>ptr</var> to <code>NULL</code>. </p></dd></dl> <dl> <dt><a name="index-SHLIB_005fSUFFIX"></a>Macro: <strong>SHLIB_SUFFIX</strong></dt> <dd><p>Define this macro to a C string constant containing the default shared library extension of the target (e.g., ‘<samp>".so"</samp>’). <code>collect2</code> strips version information after this suffix when generating global constructor and destructor names. This define is only needed on targets that use <code>collect2</code> to process constructors and destructors. </p></dd></dl> <hr> <div class="header"> <p> Next: <a href="Instruction-Output.html#Instruction-Output" accesskey="n" rel="next">Instruction Output</a>, Previous: <a href="Initialization.html#Initialization" accesskey="p" rel="prev">Initialization</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> </div> </body> </html>