[PATCH] "used" attribute saves decl from linker garbage collection

Hans-Peter Nilsson hp@bitrange.com
Thu Nov 5 11:21:21 GMT 2020


On Wed, 4 Nov 2020, H.J. Lu wrote:
> .retain is ill-defined.   For example,
>
> [hjl@gnu-cfl-2 gcc]$ cat /tmp/x.c
> static int xyzzy __attribute__((__used__));
> [hjl@gnu-cfl-2 gcc]$ ./xgcc -B./ -S /tmp/x.c -fcommon
> [hjl@gnu-cfl-2 gcc]$ cat x.s
> .file "x.c"
> .text
> .retain xyzzy  <<<<<<<<< What does it do?
> .local xyzzy
> .comm xyzzy,4,4
> .ident "GCC: (GNU) 11.0.0 20201103 (experimental)"
> .section .note.GNU-stack,"",@progbits
> [hjl@gnu-cfl-2 gcc]$

To answer that question: it's up to the assembler, but for ELF
and SHF_GNU_RETAIN, it seems obvious it'd tell the assembler to
set SHF_GNU_RETAIN for the section where the symbol ends up.
We both know this isn't rocket science with binutils.

brgds, H-P


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