From 2ee86d20e49985b903b78ebcfa3fa672e73e93aa Mon Sep 17 00:00:00 2001 From: Lasse Collin Date: Fri, 17 Feb 2023 20:48:28 +0200 Subject: [PATCH] Build: Use only the generic symbol versioning on MicroBlaze. On MicroBlaze, GCC 12 is broken in sense that __has_attribute(__symver__) returns true but it still doesn't support the __symver__ attribute even though the platform is ELF and symbol versioning is supported if using the traditional __asm__(".symver ...") method. Avoiding the traditional method is good because it breaks LTO (-flto) builds with GCC. See also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766 For now the only extra symbols in liblzma_linux.map are the compatibility symbols with the patch that spread from RHEL/CentOS 7. These require the use of __symver__ attribute or __asm__(".symver ...") in the C code. Compatibility with the patch from CentOS 7 doesn't seem valuable on MicroBlaze so use liblzma_generic.map on MicroBlaze instead. It doesn't require anything special in the C code and thus no LTO issues either. An alternative would be to detect support for __symver__ attribute in configure.ac and CMakeLists.txt and fall back to __asm__(".symver ...") but then LTO would be silently broken on MicroBlaze. It sounds likely that MicroBlaze is a special case so let's treat it as a such because that is simpler. If a similar issue exists on some other platform too then hopefully someone will report it and this can be reconsidered. (This doesn't do the same fix in CMakeLists.txt. Perhaps it should but perhaps CMake build of liblzma doesn't matter much on MicroBlaze. The problem breaks the build so it's easy to notice and can be fixed later.) Thanks to Vincent Fazio for reporting the problem and proposing a patch (in the end that solution wasn't used): https://github.com/tukaani-project/xz/pull/32 --- configure.ac | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/configure.ac b/configure.ac index 5ad55898..ad94e01a 100644 --- a/configure.ac +++ b/configure.ac @@ -758,8 +758,16 @@ elif test "x$enable_shared" = xno ; then enable_symbol_versions=no AC_MSG_RESULT([no (not building a shared library)]) else - case $host_os in - linux*) + case "$host_cpu-$host_os" in + microblaze*) + # GCC 12 on MicroBlaze doesn't support __symver__ + # attribute. It's simplest and safest to use the + # generic version on that platform since then only + # the linker script is needed. The RHEL/CentOS 7 + # compatibility symbols don't matter on MicroBlaze. + enable_symbol_versions=generic + ;; + *-linux*) case "$pic_mode-$enable_static" in default-*) # Use symvers if PIC is defined.