diff options
| author | Ulf Hermann <ulf.hermann@qt.io> | 2017-08-18 13:06:36 +0200 |
|---|---|---|
| committer | Mark Wielaard <mark@klomp.org> | 2017-08-18 22:32:44 +0200 |
| commit | 1127470a3ebf507981af5d2864bfe57ee67e868a (patch) | |
| tree | ddc7c4eb260bdb5cc677d7af958618f5a779d0ae /configure.ac | |
| parent | 07737584e73714eff3481fcf17f9f0331c8a5b88 (diff) | |
Check if gcc complains about __attribute__ (visibility(..))
If so, define attribute_hidden to be empty. Also, use attribute_hidden
in all places where we hide symbols. If this attribute is missing, it
simply means that we cannot hide private symbols in the binary using
attributes. This disables some optimizations and may increase the risk
of symbol name clashes with other libraries, but is not fatal.
However, we still employ linker version scripts to explicitly define
the exported symbols. This serves much of the same purpose. Also, as
all our symbols are prefixed with the library name, and "__" for
private ones, the chance of clashes is low anyway.
Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>
Diffstat (limited to 'configure.ac')
| -rw-r--r-- | configure.ac | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/configure.ac b/configure.ac index e6e3b675..c4fc7e3d 100644 --- a/configure.ac +++ b/configure.ac @@ -127,6 +127,22 @@ CFLAGS="$old_CFLAGS"]) AS_IF([test "x$ac_cv_c99" != xyes], AC_MSG_ERROR([gcc with GNU99 support required])) +AC_CACHE_CHECK([whether gcc supports __attribute__((visibility()))], + ac_cv_visibility, [dnl +save_CFLAGS="$CFLAGS" +CFLAGS="$save_CFLAGS -Werror" +AC_COMPILE_IFELSE([AC_LANG_SOURCE([dnl +int __attribute__((visibility("hidden"))) +foo (int a) +{ + return a; +}])], ac_cv_visibility=yes, ac_cv_visibility=no) +CFLAGS="$save_CFLAGS"]) +if test "$ac_cv_visibility" = "yes"; then + AC_DEFINE([HAVE_VISIBILITY], [1], + [Defined if __attribute__((visibility())) is supported]) +fi + AC_CACHE_CHECK([whether gcc supports -fPIC], ac_cv_fpic, [dnl save_CFLAGS="$CFLAGS" CFLAGS="$save_CFLAGS -fPIC -Werror" |