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[build] Refine the -Wno-attribute test to check our use cases.

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We don't actually check that -Wno-attribute does what
we think it does.  On clang it doesn't since it happily
seems to recognize but ignore the attribute.

This patch factors out a silent version of CAIRO_CC_TRY_FLAG
which accepts an optional program argument and actually tests
that the compiler doesn't produce any warning messages.  It
is then used to check that -Wno-attribute doesn't complain
when the __warn_unused_result__ attribute is applied to
void functions or variables.
This commit is contained in:
M Joonas Pihlaja 2009-09-02 04:10:39 +01:00
parent c87b366bfe
commit f081a5ff55
3 changed files with 43 additions and 15 deletions
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46
build/aclocal.cairo.m4
View file

@ -75,21 +75,47 @@ AC_DEFUN([CAIRO_CONFIG_COMMANDS],
], $3)
])
dnl check compiler flags
AC_DEFUN([CAIRO_CC_TRY_FLAG],
[dnl
AC_MSG_CHECKING([whether $CC supports $1])
dnl check compiler flags with a program and no muttering.
AC_DEFUN([CAIRO_CC_TRY_FLAG_SILENT],
[dnl (flags..., optional program, true-action, false-action)
_compile_program='$2'
if test "x$_compile_program" = "x"; then
# AC_LANG_PROGRAM() produces a main() w/o args,
# but -Wold-style-definition doesn't like that.
# We need _some_ program so that we don't get
# warnings about empty compilation units.
_compile_program='
int main(int c, char **v) {
(void)c; (void)v; return 0; }'
fi
_save_cflags="$CFLAGS"
CFLAGS="$CFLAGS -Werror $1"
AC_COMPILE_IFELSE([ ], [cairo_cc_flag=yes], [cairo_cc_flag=no])
CFLAGS="$CFLAGS $1"
AC_COMPILE_IFELSE(
[$_compile_program],
[cairo_cc_stderr=`test -f conftest.err && cat conftest.err`
cairo_cc_flag=yes],
[cairo_cc_stderr=`test -f conftest.err && cat conftest.err`
cairo_cc_flag=no])
CFLAGS="$_save_cflags"
if test "x$cairo_cc_flag" = "xyes"; then
ifelse([$2], , :, [$2])
else
ifelse([$3], , :, [$3])
if test "x$cairo_cc_stderr" != "x"; then
cairo_cc_flag=no
fi
if test "x$cairo_cc_flag" = "xyes"; then
ifelse([$3], , :, [$3])
else
ifelse([$4], , :, [$4])
fi
])
dnl check compiler flags possibly using -Werror if available.
AC_DEFUN([CAIRO_CC_TRY_FLAG],
[dnl (flags..., optional program, true-action, false-action)
AC_MSG_CHECKING([whether $CC supports $1])
CAIRO_CC_TRY_FLAG_SILENT([-Werror $1], [$2], [$3], [$4])
AC_MSG_RESULT([$cairo_cc_flag])
])

2
build/configure.ac.analysis
View file

@ -72,7 +72,7 @@ dnl PHP_ADD_MAKEFILE_FRAGMENT($abs_srcdir/Makefile.gcov, $abs_srcdir)
dnl In order to workaround a debian bug in libtool where they strip
dnl $dependency_libs from the link line and CFLAGS, we need to pass
dnl --coverage via LDFLAGS.
CAIRO_CC_TRY_FLAG([--coverage],
CAIRO_CC_TRY_FLAG([--coverage],,
[
CAIRO_CFLAGS="$CAIRO_CFLAGS -O0 --coverage"
CAIRO_LDFLAGS="$CAIRO_LDFLAGS -O0 --coverage"

10
build/configure.ac.warnings
View file

@ -46,7 +46,7 @@ AC_CACHE_CHECK([for supported warning flags], cairo_cv_warn_cflags, [
# last.
for W in $MAYBE_WARN; do
CAIRO_CC_TRY_FLAG([$W], [WARN_CFLAGS="$WARN_CFLAGS $W"])
CAIRO_CC_TRY_FLAG([$W],, [WARN_CFLAGS="$WARN_CFLAGS $W"])
done
cairo_cv_warn_cflags=$WARN_CFLAGS
@ -63,9 +63,11 @@ CAIRO_CFLAGS="$CAIRO_CFLAGS $WARN_CFLAGS"
AC_CACHE_CHECK([how to enable unused result warnings], cairo_cv_warn_unused_result, [
cairo_cv_warn_unused_result=""
if echo $WARN_CFLAGS | grep -e '-Wno-attributes' >/dev/null; then
AC_TRY_COMPILE([__attribute__((__warn_unused_result__))
int f (int i) { return i; }], [],
[cairo_cv_warn_unused_result="__attribute__((__warn_unused_result__))"])
CAIRO_CC_TRY_FLAG_SILENT(
[-Wno-attributes],
[__attribute__((__warn_unused_result__)) void f (void) {}
__attribute__((__warn_unused_result__)) int g;],
[cairo_cv_warn_unused_result="__attribute__((__warn_unused_result__))"])
fi
])
AC_DEFINE_UNQUOTED([WARN_UNUSED_RESULT], [$cairo_cv_warn_unused_result],