142 lines
4.7 KiB
Plaintext
142 lines
4.7 KiB
Plaintext
# ===========================================================================
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# https://www.gnu.org/software/autoconf-archive/ax_gcc_var_attribute.html
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# ===========================================================================
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#
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# SYNOPSIS
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#
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# AX_GCC_VAR_ATTRIBUTE(ATTRIBUTE)
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#
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# DESCRIPTION
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#
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# This macro checks if the compiler supports one of GCC's variable
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# attributes; many other compilers also provide variable attributes with
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# the same syntax. Compiler warnings are used to detect supported
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# attributes as unsupported ones are ignored by default so quieting
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# warnings when using this macro will yield false positives.
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#
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# The ATTRIBUTE parameter holds the name of the attribute to be checked.
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#
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# If ATTRIBUTE is supported define HAVE_VAR_ATTRIBUTE_<ATTRIBUTE>.
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#
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# The macro caches its result in the ax_cv_have_var_attribute_<attribute>
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# variable.
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#
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# The macro currently supports the following variable attributes:
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#
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# aligned
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# cleanup
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# common
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# nocommon
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# deprecated
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# mode
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# packed
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# tls_model
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# unused
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# used
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# vector_size
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# weak
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# dllimport
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# dllexport
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# init_priority
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#
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# Unsupported variable attributes will be tested against a global integer
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# variable and without any arguments given to the attribute itself; the
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# result of this check might be wrong or meaningless so use with care.
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#
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# LICENSE
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#
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# Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com>
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#
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# Copying and distribution of this file, with or without modification, are
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# permitted in any medium without royalty provided the copyright notice
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# and this notice are preserved. This file is offered as-is, without any
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# warranty.
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#serial 5
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AC_DEFUN([AX_GCC_VAR_ATTRIBUTE], [
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AS_VAR_PUSHDEF([ac_var], [ax_cv_have_var_attribute_$1])
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AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [
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AC_LINK_IFELSE([AC_LANG_PROGRAM([
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m4_case([$1],
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[aligned], [
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int foo __attribute__(($1(32)));
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],
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[cleanup], [
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int bar(int *t) { return *t; };
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],
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[common], [
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int foo __attribute__(($1));
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],
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[nocommon], [
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int foo __attribute__(($1));
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],
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[deprecated], [
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int foo __attribute__(($1)) = 0;
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],
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[mode], [
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long foo __attribute__(($1(word)));
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],
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[packed], [
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struct bar {
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int baz __attribute__(($1));
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};
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],
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[tls_model], [
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__thread int bar1 __attribute__(($1("global-dynamic")));
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__thread int bar2 __attribute__(($1("local-dynamic")));
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__thread int bar3 __attribute__(($1("initial-exec")));
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__thread int bar4 __attribute__(($1("local-exec")));
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],
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[unused], [
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int foo __attribute__(($1));
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],
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[used], [
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int foo __attribute__(($1));
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],
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[vector_size], [
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int foo __attribute__(($1(16)));
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],
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[weak], [
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int foo __attribute__(($1));
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],
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[dllimport], [
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int foo __attribute__(($1));
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],
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[dllexport], [
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int foo __attribute__(($1));
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],
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[init_priority], [
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struct bar { bar() {} ~bar() {} };
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bar b __attribute__(($1(65535/2)));
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],
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[
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m4_warn([syntax], [Unsupported attribute $1, the test may fail])
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int foo __attribute__(($1));
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]
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)], [
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m4_case([$1],
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[cleanup], [
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int foo __attribute__(($1(bar))) = 0;
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foo = foo + 1;
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],
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[]
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)])
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],
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dnl GCC doesn't exit with an error if an unknown attribute is
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dnl provided but only outputs a warning, so accept the attribute
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dnl only if no warning were issued.
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[AS_IF([test -s conftest.err],
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[AS_VAR_SET([ac_var], [no])],
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[AS_VAR_SET([ac_var], [yes])])],
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[AS_VAR_SET([ac_var], [no])])
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])
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AS_IF([test yes = AS_VAR_GET([ac_var])],
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[AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_VAR_ATTRIBUTE_$1), 1,
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[Define to 1 if the system has the `$1' variable attribute])], [])
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AS_VAR_POPDEF([ac_var])
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])
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