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Message-ID: <20151117121429.GI26951@example.net>
Date: Tue, 17 Nov 2015 13:14:29 +0100
From: u-uy74@...ey.se
To: musl@...ts.openwall.com
Subject: some odd library loading errors
Hello,
The environment:
Linux 3.# on x#86
binutils 2.24
musl 1.1.8 compiled for i486
gcc 5.2.0
(the gcc has arch=i486 as the default)
No oddities were observed with the above until trying to use libatomic
which is provided by gcc-5.2.0.
The test case:
$ cat >a.c <<____
int main(){ return 0; }
____
$ gcc -o a a.c -L<path-to-gcc-5.2.0-libs> -latomic
$ LD_LIBRARY_PATH=<path-to-gcc-5.2.0-libs> ./a
Error relocating <path-to-gcc-5.2.0-libs>/libatomic.so.1: __atomic_store_8: symbol not found
Error relocating <path-to-gcc-5.2.0-libs>/libatomic.so.1: __atomic_exchange_8: symbol not found
Error relocating <path-to-gcc-5.2.0-libs>/libatomic.so.1: __atomic_load_8: symbol not found
Error relocating <path-to-gcc-5.2.0-libs>/libatomic.so.1: __atomic_compare_exchange_8: symbol not found
$
(No error if doing the same with e.g. -lgcc_s.)
Of course the symbols shown in the diagnostics *are* defined in the library.
When I look at the store_8_.o object file, I notice though that the
__atomic_store_8 is not "a function" even though the value is
the same as of select_store_8:
$ objdump -t store_8_.o
store_8_.o: file format elf32-i386
SYMBOL TABLE:
00000000 l df *ABS* 00000000 store_n.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .text.unlikely 00000000 .text.unlikely
00000030 l F .text 00000016 select_store_8
00000000 l d .debug_info 00000000 .debug_info
00000000 l d .debug_abbrev 00000000 .debug_abbrev
00000000 l d .debug_loc 00000000 .debug_loc
00000000 l d .debug_aranges 00000000 .debug_aranges
00000000 l d .debug_ranges 00000000 .debug_ranges
00000000 l d .debug_line 00000000 .debug_line
00000000 l d .debug_str 00000000 .debug_str
00000000 l d .note.GNU-stack 00000000 .note.GNU-stack
00000000 l d .eh_frame 00000000 .eh_frame
00000000 l d .comment 00000000 .comment
00000000 g F .text 0000002c .hidden libat_store_8
00000000 *UND* 00000000 .hidden libat_lock_1
00000000 *UND* 00000000 .hidden libat_unlock_1
00000000 *UND* 00000000 .hidden libat_feat1_edx
00000000 *UND* 00000000 .hidden libat_store_8_i1
00000030 g .text 00000016 __atomic_store_8
$
I would appreciate help with finding out who is doing wrong:
- gcc
- ld
- musl
- myself
and what is to be corrected to make it work.
The actual practical problem is with the mesa library not being able
to load drivers which need symbols from libatomic, but this tiny test
case ought to be working, so it is not mesa who is at fault.
This does not either seem to involve lazy binding, which is otherwise
a known source of problems for mesa.
It looks like I can avoid the usage of libatomic with
"gcc -fno-sync-libcalls"
but the behaviour seems wrong and I would rather see it fixed or otherwise
learn if I made an error.
Regards,
Rune
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