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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_gcc_var_attribute.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_GCC_VAR_ATTRIBUTE(ATTRIBUTE)
#
# DESCRIPTION
#
# This macro checks if the compiler supports one of GCC's variable
# attributes; many other compilers also provide variable 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_VAR_ATTRIBUTE_<ATTRIBUTE>.
#
# The macro caches its result in the ax_cv_have_var_attribute_<attribute>
# variable.
#
# The macro currently supports the following variable attributes:
#
# aligned
# cleanup
# common
# nocommon
# deprecated
# mode
# packed
# tls_model
# unused
# used
# vector_size
# weak
# dllimport
# dllexport
# init_priority
#
# Unsupported variable attributes will be tested against a global integer
# variable and without any arguments given to the attribute itself; the
# result of this 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 5
AC_DEFUN([AX_GCC_VAR_ATTRIBUTE], [
AS_VAR_PUSHDEF([ac_var], [ax_cv_have_var_attribute_$1])
AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [
AC_LINK_IFELSE([AC_LANG_PROGRAM([
m4_case([$1],
[aligned], [
int foo __attribute__(($1(32)));
],
[cleanup], [
int bar(int *t) { return *t; };
],
[common], [
int foo __attribute__(($1));
],
[nocommon], [
int foo __attribute__(($1));
],
[deprecated], [
int foo __attribute__(($1)) = 0;
],
[mode], [
long foo __attribute__(($1(word)));
],
[packed], [
struct bar {
int baz __attribute__(($1));
};
],
[tls_model], [
__thread int bar1 __attribute__(($1("global-dynamic")));
__thread int bar2 __attribute__(($1("local-dynamic")));
__thread int bar3 __attribute__(($1("initial-exec")));
__thread int bar4 __attribute__(($1("local-exec")));
],
[unused], [
int foo __attribute__(($1));
],
[used], [
int foo __attribute__(($1));
],
[vector_size], [
int foo __attribute__(($1(16)));
],
[weak], [
int foo __attribute__(($1));
],
[dllimport], [
int foo __attribute__(($1));
],
[dllexport], [
int foo __attribute__(($1));
],
[init_priority], [
struct bar { bar() {} ~bar() {} };
bar b __attribute__(($1(65535/2)));
],
[
m4_warn([syntax], [Unsupported attribute $1, the test may fail])
int foo __attribute__(($1));
]
)], [
m4_case([$1],
[cleanup], [
int foo __attribute__(($1(bar))) = 0;
foo = foo + 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_VAR_ATTRIBUTE_$1), 1,
[Define to 1 if the system has the `$1' variable attribute])], [])
AS_VAR_POPDEF([ac_var])
])
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