diff options
Diffstat (limited to 'src/liblzma/common/common.h')
| -rw-r--r-- | src/liblzma/common/common.h | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/liblzma/common/common.h b/src/liblzma/common/common.h index 36366dbc..4783e45d 100644 --- a/src/liblzma/common/common.h +++ b/src/liblzma/common/common.h @@ -34,6 +34,34 @@ #include "lzma.h" +#ifdef HAVE_SYMBOL_VERSIONS_LINUX +// To keep link-time optimization (LTO, -flto) working with GCC, +// the __symver__ attribute must be used instead of __asm__(".symver ..."). +// Otherwise the symbol versions may be lost, resulting in broken liblzma +// that has wrong default versions in the exported symbol list! +// The attribute was added in GCC 10; LTO with older GCC is not supported. +// +// To keep -Wmissing-prototypes happy, use LZMA_SYMVER_API only with function +// declarations (including those with __alias__ attribute) and LZMA_API with +// the function definitions. This means a little bit of silly copy-and-paste +// between declarations and definitions though. +// +// As of GCC 12.2, the __symver__ attribute supports only @ and @@ but the +// very convenient @@@ isn't supported (it's supported by GNU assembler +// since 2000). When using @@ instead of @@@, the internal name must not be +// the same as the external name to avoid problems in some situations. This +// is why "#define foo_52 foo" is needed for the default symbol versions. +# if TUKLIB_GNUC_REQ(10, 0) +# define LZMA_SYMVER_API(extnamever, type, intname) \ + extern __attribute__((__symver__(extnamever))) \ + LZMA_API(type) intname +# else +# define LZMA_SYMVER_API(extnamever, type, intname) \ + __asm__(".symver " #intname "," extnamever); \ + extern LZMA_API(type) intname +# endif +#endif + // These allow helping the compiler in some often-executed branches, whose // result is almost always the same. #ifdef __GNUC__ |