[Bug libc/27492] Make static linking friendly with {ld.bfd,ld.lld} -z start-stop-gc: removing unused section '__libc_atexit'

["i at maskray dot me" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27492

Fangrui Song <i at maskray dot me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unspecified                 |2.33
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Fangrui Song <i at maskray dot me> ---
Fixed by
https://sourceware.org/git/?p=glibc.git;a=commit;h=cd6ae7ea5431c2b8f16201fb0e2c413bf8d2df06

commit cd6ae7ea5431c2b8f16201fb0e2c413bf8d2df06
Author: Fangrui Song <maskray@google.com>
Date:   Fri Apr 16 11:26:39 2021

    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>

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