> is there a simple macro that will test for a specific compiler flag and set
> a variable in both Makefile and config.h?
> I am looking for an easy way to test for GCC's -fvisibility=hidden and
> have an indicator whether or not it is available in said files.
Hi,
Here's (attached) a test for visibility attributes instead of
visibility flags, which might give the same effect. It defines the
config.h variables HAVE_ATTRIBUTE_VISIBILITY_HIDDEN and
HAVE_ATTRIBUTE_VISIBILITY_DEFAULT if the respective attributes are
understood. You can easily add an AM_CONDITIONAL to it as well. This
particular test runs in C++ mode. I had to temporarily add the -Werror
flag to the compile flags to make the compiler reject warnings about
unsupported attributes. Feedback is welcome.
Fang
dnl @synopsis FANG_CXX_ATTRIBUTE_VISIBILITY
dnl
dnl Checking for visibility attributes, "hidden" and "default"
dnl New since gcc-4.0.
dnl Define HAVE_ATTRIBUTE_VISIBILITY_HIDDEN if supported.
dnl Define HAVE_ATTRIBUTE_VISIBILITY_DEFAULT if supported.
dnl
dnl @category Cxx
dnl @version 2006-05-08
dnl @author David Fang <fangism@xxxxxxxxxxxxxxxxxxxxx>
dnl @license AllPermissive
dnl
AC_DEFUN([FANG_CXX_ATTRIBUTE_VISIBILITY],
[
AC_LANG_PUSH(C++)
saved_CXXFLAGS=$CXXFLAGS
CXXFLAGS="$saved_CXXFLAGS -Werror"
dnl check for __visibility__(("hidden"))
AC_CACHE_CHECK([whether compiler accepts __attribute__((visibility("hidden")))],
[fang_cv_cxx_attribute_visibility_hidden],
AC_COMPILE_IFELSE(
AC_LANG_PROGRAM(
[struct __attribute__((visibility("hidden"))) foo {
foo() { }
~foo() { }
};],
[foo bar;]),
[fang_cv_cxx_attribute_visibility_hidden=yes],
[fang_cv_cxx_attribute_visibility_hidden=no]
)
)
if test "$fang_cv_cxx_attribute_visibility_hidden" = "yes"; then
AC_DEFINE(HAVE_ATTRIBUTE_VISIBILITY_HIDDEN, [],
[True if compiler supports __attribute__((visibility("hidden"))) ])
fi
dnl check for __visibility__(("default"))
AC_CACHE_CHECK([whether compiler accepts __attribute__((visibility("default")))],
[fang_cv_cxx_attribute_visibility_default],
AC_COMPILE_IFELSE(
AC_LANG_PROGRAM(
[struct __attribute__((visibility("default"))) foo {
foo() { }
~foo() { }
};],
[foo bar;]),
[fang_cv_cxx_attribute_visibility_default=yes],
[fang_cv_cxx_attribute_visibility_default=no]
)
)
if test "$fang_cv_cxx_attribute_visibility_default" = "yes"; then
AC_DEFINE(HAVE_ATTRIBUTE_VISIBILITY_DEFAULT, [],
[True if compiler supports __attribute__((visibility("default"))) ])
fi
dnl restore flags and language
CXXFLAGS=$saved_CXXFLAGS
AC_LANG_POP(C++)
])dnl
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