# =========================================================================== # https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html # =========================================================================== # # SYNOPSIS # # AX_GCC_FUNC_ATTRIBUTE(ATTRIBUTE) # # DESCRIPTION # # This macro checks if the compiler supports one of GCC's function # attributes; many other compilers also provide function attributes with # the same syntax. Compiler warnings are used to detect supported # attributes as unsupported ones are ignored by default so quieting # warnings when using this macro will yield false positives. # # The ATTRIBUTE parameter holds the name of the attribute to be checked. # # If ATTRIBUTE is supported define HAVE_FUNC_ATTRIBUTE_<ATTRIBUTE>. # # The macro caches its result in the ax_cv_have_func_attribute_<attribute> # variable. # # The macro currently supports the following function attributes: # # alias # aligned # alloc_size # always_inline # artificial # cold # const # constructor # constructor_priority for constructor attribute with priority # deprecated # destructor # dllexport # dllimport # error # externally_visible # fallthrough # flatten # format # format_arg # gnu_inline # hot # ifunc # leaf # malloc # noclone # noinline # nonnull # noreturn # nothrow # optimize # pure # sentinel # sentinel_position # unused # used # visibility # warning # warn_unused_result # weak # weakref # # Unsupported function attributes will be tested with a prototype # returning an int and not accepting any arguments and the result of the # check might be wrong or meaningless so use with care. # # LICENSE # # Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com> # # Copying and distribution of this file, with or without modification, are # permitted in any medium without royalty provided the copyright notice # and this notice are preserved. This file is offered as-is, without any # warranty. #serial 9 AC_DEFUN([AX_GCC_FUNC_ATTRIBUTE], [ AS_VAR_PUSHDEF([ac_var], [ax_cv_have_func_attribute_$1]) AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [ AC_LINK_IFELSE([AC_LANG_PROGRAM([ m4_case([$1], [alias], [ int foo( void ) { return 0; } int bar( void ) __attribute__(($1("foo"))); ], [aligned], [ int foo( void ) __attribute__(($1(32))); ], [alloc_size], [ void *foo(int a) __attribute__(($1(1))); ], [always_inline], [ inline __attribute__(($1)) int foo( void ) { return 0; } ], [artificial], [ inline __attribute__(($1)) int foo( void ) { return 0; } ], [cold], [ int foo( void ) __attribute__(($1)); ], [const], [ int foo( void ) __attribute__(($1)); ], [constructor_priority], [ int foo( void ) __attribute__((__constructor__(65535/2))); ], [constructor], [ int foo( void ) __attribute__(($1)); ], [deprecated], [ int foo( void ) __attribute__(($1(""))); ], [destructor], [ int foo( void ) __attribute__(($1)); ], [dllexport], [ __attribute__(($1)) int foo( void ) { return 0; } ], [dllimport], [ int foo( void ) __attribute__(($1)); ], [error], [ int foo( void ) __attribute__(($1(""))); ], [externally_visible], [ int foo( void ) __attribute__(($1)); ], [fallthrough], [ int foo( void ) {switch (0) { case 1: __attribute__(($1)); case 2: break ; }}; ], [flatten], [ int foo( void ) __attribute__(($1)); ], [format], [ int foo(const char *p, ...) __attribute__(($1(printf, 1, 2))); ], [format_arg], [ char *foo(const char *p) __attribute__(($1(1))); ], [gnu_inline], [ inline __attribute__(($1)) int foo( void ) { return 0; } ], [hot], [ int foo( void ) __attribute__(($1)); ], [ifunc], [ int my_foo( void ) { return 0; } static int (*resolve_foo(void))(void) { return my_foo; } int foo( void ) __attribute__(($1("resolve_foo"))); ], [leaf], [ __attribute__(($1)) int foo( void ) { return 0; } ], [malloc], [ void *foo( void ) __attribute__(($1)); ], [noclone], [ int foo( void ) __attribute__(($1)); ], [noinline], [ __attribute__(($1)) int foo( void ) { return 0; } ], [nonnull], [ int foo(char *p) __attribute__(($1(1))); ], [noreturn], [ void foo( void ) __attribute__(($1)); ], [nothrow], [ int foo( void ) __attribute__(($1)); ], [optimize], [ __attribute__(($1(3))) int foo( void ) { return 0; } ], [pure], [ int foo( void ) __attribute__(($1)); ], [sentinel], [ int foo(void *p, ...) __attribute__(($1)); ], [sentinel_position], [ int foo(void *p, ...) __attribute__(($1(1))); ], [returns_nonnull], [ void *foo( void ) __attribute__(($1)); ], [unused], [ int foo( void ) __attribute__(($1)); ], [used], [ int foo( void ) __attribute__(($1)); ], [visibility], [ int foo_def( void ) __attribute__(($1("default"))); int foo_hid( void ) __attribute__(($1("hidden"))); int foo_int( void ) __attribute__(($1("internal"))); int foo_pro( void ) __attribute__(($1("protected"))); ], [warning], [ int foo( void ) __attribute__(($1(""))); ], [warn_unused_result], [ int foo( void ) __attribute__(($1)); ], [weak], [ int foo( void ) __attribute__(($1)); ], [weakref], [ static int foo( void ) { return 0; } static int bar( void ) __attribute__(($1("foo"))); ], [target], [ static int bar( void ) __attribute__(($1("sse2"))); ], [ m4_warn([syntax], [Unsupported attribute $1, the test may fail]) int foo( void ) __attribute__(($1)); ] )], []) ], dnl GCC doesn't exit with an error if an unknown attribute is dnl provided but only outputs a warning, so accept the attribute dnl only if no warning were issued. [AS_IF([test -s conftest.err], [AS_VAR_SET([ac_var], [no])], [AS_VAR_SET([ac_var], [yes])])], [AS_VAR_SET([ac_var], [no])]) ]) AS_IF([test yes = AS_VAR_GET([ac_var])], [AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_FUNC_ATTRIBUTE_$1), 1, [Define to 1 if the system has the `$1' function attribute])], []) AS_VAR_POPDEF([ac_var]) ])