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#
# SYNOPSIS
#
# DLP_FALLTHROUGH
#
# DESCRIPTION
#
# This macro checks if the compiler supports a fallthrough warning
# suppression attribute in GCC or CLANG style.
#
# If a fallthrough warning suppression attribute is supported define
# HAVE_<STYLE>_ATTRIBUTE_FALLTHROUGH.
#
# The macro caches its result in ax_cv_have_<style>_attribute_fallthrough
# variables.
#
# LICENSE
#
# Copyright (c) 2017 David Tardon <dtardon@redhat.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 1
m4_defun([_DLP_FALLTHROUGH], [
AS_VAR_PUSHDEF([ac_var], [ax_cv_have_$2_attribute_falltrough])
AC_CACHE_CHECK([for $1], [ac_var], [
AC_LINK_IFELSE([AC_LANG_PROGRAM([
void foo(int &i)
{
switch (i)
{
case 0:
i += 1;
$1;
default:
i += 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_$3_ATTRIBUTE_FALLTHROUGH), 1,
[Define to 1 if the system has the $4-style `fallthrough' attribute])], [])
AS_VAR_POPDEF([ac_var])
])
AC_DEFUN([DLP_FALLTHROUGH], [
_DLP_FALLTHROUGH([[__attribute__((fallthrough))]], [gcc], [GCC], [GNU])
_DLP_FALLTHROUGH([[[[clang::fallthrough]]]], [clang], [CLANG], [clang])
])
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