https://sourceware.org/bugzilla/show_bug.cgi?id=23268
--- Comment #1 from Mike Hommey <mh-sourceware at glandium dot org> ---
As for what kind of subtle problem this can cause:
$ cat foo.c
#include <stdlib.h>
void* malloc_hook(size_t s) {
abort();
}
void* (*__malloc_hook)(size_t s) = malloc_hook;
int main() { malloc(1);}
$ cat ver
hidden {
local: main;
};
$ gcc -o foo foo.c -rdynamic -Wl,--version-script,ver
# Aborted means we got in the hook.
$ ./foo
Aborted
$ gcc -o foo foo.c -rdynamic -Wl,--version-script,ver -fuse-ld=gold
$ ./foo
No output in this case, because the hook is not found by ld.so:
$ LD_DEBUG=bindings ./foo 2>&1 | grep malloc_hook
1531: binding file /lib/x86_64-linux-gnu/libc.so.6 [0] to
/lib/x86_64-linux-gnu/libc.so.6 [0]: normal symbol `__malloc_hook'
[GLIBC_2.2.5]
The reason being that since __malloc_hook has a symbol version (that thanks to
bug 23267, neither objdump nor readelf show), ld.so doesn't pick it up because
the symbol version doesn't match GLIBC_2.2.5.
(Yes, the version script is a little contrived, for $reasons ; but this would
happen with a version script that exports other symbols with a symbol version
too)
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