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Build: Fix ax_gcc_func_attribute.m4 for compilers other than GCC >= 4.6. 

With other compilers it accepted all attributes as it didn't recognize
the warning messages about unsupported attributes. The problem occurs
only with compilers that warn instead of error when an unsupported
attribute is seen.

FIXME? gnu_format is broken but so it was before.
This commit is contained in:
Lasse Collin 2023-10-16 17:41:22 +03:00
parent ab2e9be00a
commit 8a8b8042e7
1 changed files with 41 additions and 4 deletions
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45
m4/ax_gcc_func_attribute.m4
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@ -1,5 +1,9 @@
# =========================================================================== # ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html # https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html
#
# NOTE: This is a modified version! This has a fix for the grep pattern
# to make it detect unsupported attributes with GCC < 4.6, Clang >= 3.5,
# ICC, Solaris Studio, XL C, and CompCert.
# =========================================================================== # ===========================================================================
# #
# SYNOPSIS # SYNOPSIS
@ -69,6 +73,38 @@
# returning an int and not accepting any arguments and the result of the # returning an int and not accepting any arguments and the result of the
# check might be wrong or meaningless so use with care. # check might be wrong or meaningless so use with care.
# #
# The following are known to only warn about unsupported attributes:
# GCC, Clang/LLVM and Clang-based compilers, Intel C Compiler Classic (ICC),
# Oracle Solaris Studio, IBM XL C, and CompCert. Examples:
#
# GCC <= 4.5.3:
# warning: 'foobar' attribute directive ignored
#
# GCC >= 4.6:
# warning: 'foobar' attribute directive ignored [-Wattributes]
#
# Clang < 3.5:
# warning: unknown attribute 'foobar' ignored [-Wattributes]
#
# Clang >= 3.5, CompCert:
# warning: unknown attribute 'foobar' ignored [-Wunknown-attributes]
#
# ICC:
# warning #1292: unknown attribute "foobar"
#
# Solaris Studio:
# warning: attribute "foobar" is unknown, ignored
#
# XL C message might not contain "warning" but might contain
# "WARNING" (z/OS) or "(W)" (AIX). Documentation lists many
# attribute-related messages but they all contain the strings
# "Attribute" or "attribute" and "ignored". For example:
# Attribute "foobar" is not supported and is ignored.
#
# The regex ' [Aa]ttribute .* ignored' matches all the above except
# ICC. It can be matched with ': unknown attribute' which happens to
# match Clang too.
#
# LICENSE # LICENSE
# #
# Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com> # Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com>
@ -225,10 +261,11 @@ AC_DEFUN([AX_GCC_FUNC_ATTRIBUTE], [
] ]
)], []) )], [])
], ],
dnl GCC doesn't exit with an error if an unknown attribute is dnl Some compilers don't exit with an error if an unknown
dnl provided but only outputs a warning, so accept the attribute dnl attribute is provided. They only output a warning, so accept
dnl only if no warning were issued. dnl the attribute only if no attribute-related warnings were issued.
[AS_IF([grep -- -Wattributes conftest.err], [AS_IF([[grep ' [Aa]ttribute .* ignored' conftest.err >/dev/null \
|| grep ': unknown attribute' conftest.err >/dev/null]],
[AS_VAR_SET([ac_var], [no])], [AS_VAR_SET([ac_var], [no])],
[AS_VAR_SET([ac_var], [yes])])], [AS_VAR_SET([ac_var], [yes])])],
[AS_VAR_SET([ac_var], [no])]) [AS_VAR_SET([ac_var], [no])])