From a338f624711a63b89ce97bb0a69cda5c99ff8f61 Mon Sep 17 00:00:00 2001 From: Lasse Collin Date: Sun, 15 Oct 2023 02:20:47 +0300 Subject: [PATCH] CMake: Don't assume that -fvisibility=hidden is supported outside Windows. The original code was good enough for supporting GNU/Linux and a few others but it wasn't very portable. --- CMakeLists.txt | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/CMakeLists.txt b/CMakeLists.txt index 51635505..c37c92b0 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -862,10 +862,30 @@ if(HAVE_IMMINTRIN_H) tuklib_add_definition_if(liblzma HAVE_USABLE_CLMUL) endif() -# Support -fvisiblity=hidden when building shared liblzma. -# These lines do nothing on Windows (even under Cygwin). -# HAVE_VISIBILITY should always be defined to 0 or 1. -if(BUILD_SHARED_LIBS) +# Symbol visibility support: +# +# The C_VISIBILITY_PRESET property takes care of adding the compiler +# option -fvisibility=hidden (or equivalent) if and only if it is supported. +# +# HAVE_VISIBILITY indicates if __attribute__((__visibility__("default"))) +# is supported. HAVE_VISIBILITY is ignored on Windows and Cygwin in +# the C code so we don't need to handle that here. HAVE_VISIBILITY +# should always be defined to 0 or 1. +# +# CMake's GenerateExportHeader module is too fancy since liblzma already +# has the necessary macros. Instead, check CMake's internal variable +# CMAKE_C_COMPILE_OPTIONS_VISIBILITY (it's the C-specific variant of +# CMAKE__COMPILE_OPTIONS_VISIBILITY) which contains the string or +# substring "-fvisibility=" when that compiler option is supported (due to +# the possibility of substring, we use MATCHES instead of STREQUAL). It's +# empty or unset when visibility isn't supported. +# +# NOTE: CMake 3.27 doesn't support other visibility mechanisms. For example, +# SolarisStudio ("SunPro") has the option -xldscope=hidden and uses __global +# instead of GNU C's __attribute__ to mark exported symbols. Autotools-based +# build doesn't support -xldscope=hidden either. +if(BUILD_SHARED_LIBS + AND CMAKE_C_COMPILE_OPTIONS_VISIBILITY MATCHES "-fvisibility=") set_target_properties(liblzma PROPERTIES C_VISIBILITY_PRESET hidden) target_compile_definitions(liblzma PRIVATE HAVE_VISIBILITY=1) else()