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| author | Fangrui Song <maskray@google.com> | 2021-04-16 11:26:39 -0700 |
|---|---|---|
| committer | Fangrui Song <maskray@google.com> | 2021-08-31 15:36:41 -0700 |
| commit | add8e34cd7223dc6770c34de820651eee879ff65 (patch) | |
| tree | 1c4ce7396339c339508a0e7f783740f4c31c60a3 /include/libc-symbols.h | |
| parent | bc129fb15b826520d16656df99a29910a487c252 (diff) | |
| download | glibc-add8e34cd7223dc6770c34de820651eee879ff65.zip glibc-add8e34cd7223dc6770c34de820651eee879ff65.tar.gz glibc-add8e34cd7223dc6770c34de820651eee879ff65.tar.bz2 | |
Set the retain attribute on _elf_set_element if CC supports [BZ #27492]
So that text_set_element/data_set_element/bss_set_element defined
variables will be retained by the linker.
Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable
will not be optimized out; 'retain' prevents section garbage collection
if the linker support SHF_GNU_RETAIN.
GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C
identifier name sections to be GCed even if there are live
__start_/__stop_ references.
Without the change, there are some static linking problems, e.g.
_IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so
stdout is not flushed on exit.
Note: GCC may warning 'retain' attribute ignored while __has_attribute(retain)
is 1 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587).
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit cd6ae7ea5431c2b8f16201fb0e2c413bf8d2df06)
Diffstat (limited to 'include/libc-symbols.h')
| -rw-r--r-- | include/libc-symbols.h | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/include/libc-symbols.h b/include/libc-symbols.h index c40f5fb..1e00fcb 100644 --- a/include/libc-symbols.h +++ b/include/libc-symbols.h @@ -286,6 +286,12 @@ for linking") */ +#ifdef HAVE_GNU_RETAIN +# define attribute_used_retain __attribute__ ((__used__, __retain__)) +#else +# define attribute_used_retain __attribute__ ((__used__)) +#endif + /* Symbol set support macros. */ /* Make SYMBOL, which is in the text segment, an element of SET. */ @@ -301,12 +307,12 @@ for linking") /* When building a shared library, make the set section writable, because it will need to be relocated at run time anyway. */ # define _elf_set_element(set, symbol) \ - static const void *__elf_set_##set##_element_##symbol##__ \ - __attribute__ ((used, section (#set))) = &(symbol) + static const void *__elf_set_##set##_element_##symbol##__ \ + attribute_used_retain __attribute__ ((section (#set))) = &(symbol) #else # define _elf_set_element(set, symbol) \ - static const void *const __elf_set_##set##_element_##symbol##__ \ - __attribute__ ((used, section (#set))) = &(symbol) + static const void *const __elf_set_##set##_element_##symbol##__ \ + attribute_used_retain __attribute__ ((section (#set))) = &(symbol) #endif /* Define SET as a symbol set. This may be required (it is in a.out) to |