1 # ===========================================================================
2 # https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html
3 # ===========================================================================
7 # AX_GCC_FUNC_ATTRIBUTE(ATTRIBUTE)
11 # This macro checks if the compiler supports one of GCC's function
12 # attributes; many other compilers also provide function attributes with
13 # the same syntax. Compiler warnings are used to detect supported
14 # attributes as unsupported ones are ignored by default so quieting
15 # warnings when using this macro will yield false positives.
17 # The ATTRIBUTE parameter holds the name of the attribute to be checked.
19 # If ATTRIBUTE is supported define HAVE_FUNC_ATTRIBUTE_<ATTRIBUTE>.
21 # The macro caches its result in the ax_cv_have_func_attribute_<attribute>
24 # The macro currently supports the following function attributes:
34 # constructor_priority for constructor attribute with priority
67 # Unsupported function attributes will be tested with a prototype
68 # returning an int and not accepting any arguments and the result of the
69 # check might be wrong or meaningless so use with care.
73 # Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com>
75 # Copying and distribution of this file, with or without modification, are
76 # permitted in any medium without royalty provided the copyright notice
77 # and this notice are preserved. This file is offered as-is, without any
82 AC_DEFUN([AX_GCC_FUNC_ATTRIBUTE], [
83 AS_VAR_PUSHDEF([ac_var], [ax_cv_have_func_attribute_$1])
85 AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [
86 AC_LINK_IFELSE([AC_LANG_PROGRAM([
89 int foo( void ) { return 0; }
90 int bar( void ) __attribute__(($1("foo")));
93 int foo( void ) __attribute__(($1(32)));
96 void *foo(int a) __attribute__(($1(1)));
99 inline __attribute__(($1)) int foo( void ) { return 0; }
102 inline __attribute__(($1)) int foo( void ) { return 0; }
105 int foo( void ) __attribute__(($1));
108 int foo( void ) __attribute__(($1));
110 [constructor_priority], [
111 int foo( void ) __attribute__((__constructor__(65535/2)));
114 int foo( void ) __attribute__(($1));
117 int foo( void ) __attribute__(($1("")));
120 int foo( void ) __attribute__(($1));
123 __attribute__(($1)) int foo( void ) { return 0; }
126 int foo( void ) __attribute__(($1));
129 int foo( void ) __attribute__(($1("")));
131 [externally_visible], [
132 int foo( void ) __attribute__(($1));
135 int foo( void ) {switch (0) { case 1: __attribute__(($1)); case 2: break ; }};
138 int foo( void ) __attribute__(($1));
141 int foo(const char *p, ...) __attribute__(($1(printf, 1, 2)));
144 char *foo(const char *p) __attribute__(($1(1)));
147 inline __attribute__(($1)) int foo( void ) { return 0; }
150 int foo( void ) __attribute__(($1));
153 int my_foo( void ) { return 0; }
154 static int (*resolve_foo(void))(void) { return my_foo; }
155 int foo( void ) __attribute__(($1("resolve_foo")));
158 __attribute__(($1)) int foo( void ) { return 0; }
161 void *foo( void ) __attribute__(($1));
164 int foo( void ) __attribute__(($1));
167 __attribute__(($1)) int foo( void ) { return 0; }
170 int foo(char *p) __attribute__(($1(1)));
173 void foo( void ) __attribute__(($1));
176 int foo( void ) __attribute__(($1));
179 __attribute__(($1(3))) int foo( void ) { return 0; }
182 int foo( void ) __attribute__(($1));
185 int foo(void *p, ...) __attribute__(($1));
187 [sentinel_position], [
188 int foo(void *p, ...) __attribute__(($1(1)));
191 void *foo( void ) __attribute__(($1));
194 int foo( void ) __attribute__(($1));
197 int foo( void ) __attribute__(($1));
200 int foo_def( void ) __attribute__(($1("default")));
201 int foo_hid( void ) __attribute__(($1("hidden")));
202 int foo_int( void ) __attribute__(($1("internal")));
203 int foo_pro( void ) __attribute__(($1("protected")));
206 int foo( void ) __attribute__(($1("")));
208 [warn_unused_result], [
209 int foo( void ) __attribute__(($1));
212 int foo( void ) __attribute__(($1));
215 static int foo( void ) { return 0; }
216 static int bar( void ) __attribute__(($1("foo")));
219 m4_warn([syntax], [Unsupported attribute $1, the test may fail])
220 int foo( void ) __attribute__(($1));
224 dnl GCC doesn't exit with an error if an unknown attribute is
225 dnl provided but only outputs a warning, so accept the attribute
226 dnl only if no warning were issued.
227 [AS_IF([test -s conftest.err],
228 [AS_VAR_SET([ac_var], [no])],
229 [AS_VAR_SET([ac_var], [yes])])],
230 [AS_VAR_SET([ac_var], [no])])
233 AS_IF([test yes = AS_VAR_GET([ac_var])],
234 [AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_FUNC_ATTRIBUTE_$1), 1,
235 [Define to 1 if the system has the `$1' function attribute])], [])
237 AS_VAR_POPDEF([ac_var])