1 dnl Copyright 2010 The Kyua Authors.
2 dnl All rights reserved.
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5 dnl modification, are permitted provided that the following conditions are
8 dnl * Redistributions of source code must retain the above copyright
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10 dnl * Redistributions in binary form must reproduce the above copyright
11 dnl notice, this list of conditions and the following disclaimer in the
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13 dnl * Neither the name of Google Inc. nor the names of its contributors
14 dnl may be used to endorse or promote products derived from this software
15 dnl without specific prior written permission.
17 dnl THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 dnl "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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26 dnl (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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29 dnl \file compiler-flags.m4
31 dnl Macros to check for the existence of compiler flags. The macros in this
32 dnl file support both C and C++.
34 dnl Be aware that, in order to detect a flag accurately, we may need to enable
35 dnl strict warning checking in the compiler (i.e. enable -Werror). Some
36 dnl compilers, e.g. Clang, report unknown -W flags as warnings unless -Werror is
37 dnl selected. This fact would confuse the flag checks below because we would
38 dnl conclude that a flag is valid while in reality it is not. To resolve this,
39 dnl the macros below will pass -Werror to the compiler along with any other flag
43 dnl Checks for a compiler flag and sets a result variable.
45 dnl This is an auxiliary macro for the implementation of _KYUA_FLAG.
47 dnl \param 1 The shell variable containing the compiler name. Used for
48 dnl reporting purposes only. C or CXX.
49 dnl \param 2 The shell variable containing the flags for the compiler.
50 dnl CFLAGS or CXXFLAGS.
51 dnl \param 3 The name of the compiler flag to check for.
52 dnl \param 4 The shell variable to set with the result of the test. Will
53 dnl be set to 'yes' if the flag is valid, 'no' otherwise.
54 dnl \param 5 Additional, optional flags to pass to the C compiler while
55 dnl looking for the flag in $3. We use this here to pass -Werror to the
56 dnl flag checks (unless we are checking for -Werror already).
57 AC_DEFUN([_KYUA_FLAG_AUX], [
58 if test x"${$4-unset}" = xunset; then
59 AC_MSG_CHECKING(whether ${$1} supports $3)
63 # The inclusion of a header file in the test program below is needed
64 # because some compiler flags that we test for may actually not be
65 # compatible with other flags, and such compatibility checks are
66 # performed within the system header files.
68 # As an example, if we are testing for -D_FORTIFY_SOURCE=2 and the
69 # compilation is being done with -O2, Linux's /usr/include/features.h
70 # will abort the compilation of our code later on. By including a
71 # generic header file here that pulls in features.h we ensure that
72 # this test is accurate for the build stage.
73 AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [return 0;])],
82 dnl Checks for a compiler flag and appends it to a result variable.
84 dnl \param 1 The shell variable containing the compiler name. Used for
85 dnl reporting purposes only. CC or CXX.
86 dnl \param 2 The shell variable containing the flags for the compiler.
87 dnl CFLAGS or CXXFLAGS.
88 dnl \param 3 The name of the compiler flag to check for.
89 dnl \param 4 The shell variable to which to append $3 if the flag is valid.
90 AC_DEFUN([_KYUA_FLAG], [
91 _KYUA_FLAG_AUX([$1], [$2], [-Werror], [kyua_$1_has_werror])
92 if test "$3" = "-Werror"; then
93 found=${kyua_$1_has_werror}
96 if test ${kyua_$1_has_werror} = yes; then
97 _KYUA_FLAG_AUX([$1], [$2], [$3], [found], [-Werror])
99 _KYUA_FLAG_AUX([$1], [$2], [$3], [found], [])
102 if test ${found} = yes; then
108 dnl Checks for a C compiler flag and appends it to a variable.
110 dnl \pre The current language is C.
112 dnl \param 1 The name of the compiler flag to check for.
113 dnl \param 2 The shell variable to which to append $1 if the flag is valid.
114 AC_DEFUN([KYUA_CC_FLAG], [
116 _KYUA_FLAG([CC], [CFLAGS], [$1], [$2])
120 dnl Checks for a C++ compiler flag and appends it to a variable.
122 dnl \pre The current language is C++.
124 dnl \param 1 The name of the compiler flag to check for.
125 dnl \param 2 The shell variable to which to append $1 if the flag is valid.
126 AC_DEFUN([KYUA_CXX_FLAG], [
127 AC_LANG_ASSERT([C++])
128 _KYUA_FLAG([CXX], [CXXFLAGS], [$1], [$2])
132 dnl Checks for a set of C compiler flags and appends them to CFLAGS.
134 dnl The checks are performed independently and only when all the checks are
135 dnl done, the output variable is modified.
137 dnl \param 1 Whitespace-separated list of C flags to check.
138 AC_DEFUN([KYUA_CC_FLAGS], [
142 KYUA_CC_FLAG(${f}, valid_cflags)
144 if test -n "${valid_cflags}"; then
145 CFLAGS="${CFLAGS} ${valid_cflags}"
151 dnl Checks for a set of C++ compiler flags and appends them to CXXFLAGS.
153 dnl The checks are performed independently and only when all the checks are
154 dnl done, the output variable is modified.
156 dnl \pre The current language is C++.
158 dnl \param 1 Whitespace-separated list of C flags to check.
159 AC_DEFUN([KYUA_CXX_FLAGS], [
163 KYUA_CXX_FLAG(${f}, valid_cxxflags)
165 if test -n "${valid_cxxflags}"; then
166 CXXFLAGS="${CXXFLAGS} ${valid_cxxflags}"