https://sourceware.org/bugzilla/show_bug.cgi?id=16457
Bug ID: 16457
Summary: Weak reference leads to bogus entry in .gnu.version_r
section
Product: binutils
Version: 2.24
Status: NEW
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: ldv at altlinux dot org
Weak reference may cause ld to generate an entry in .gnu.version_r section that
would reference an object not present in the dynamic section.
This actually happens with most of c++ objects that have weak references to
versioned symbols from libpthread.
Here is an artificial test case without c++ and foreign libraries:
$ cat libb.c
int fb(void){return 0;}
$ cat libb.map
FOO{global:fb;};
$ gcc -shared -Wl,-soname,libb.so,--version-script,libb.map -Wall -Werror -fPIC
-o libb.so libb.c
$ cat liba.c
int fb(void);
int fa(void){return fb();}
$ gcc -shared -Wl,--no-undefined,-soname,liba.so -Wall -Werror -fPIC -o liba.so
liba.c -L. -lb
$ cat e.c
int fa(void);
int fb(void) __attribute__((weak));
int main(void){return fb?fb():fa();}
$ gcc -Wall -Werror e.c -Wl,--rpath-link,. -L. -la -o e
$ readelf -Wd e | grep -F NEEDED
0x0000000000000001 (NEEDED) Shared library: [liba.so]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
$ readelf -WV e
Version symbols section '.gnu.version' contains 13 entries:
Addr: 00000000004004e8 Offset: 0x0004e8 Link: 5 (.dynsym)
000: 0 (*local*) 0 (*local*) 2 (GLIBC_2.2.5) 0 (*local*)
004: 0 (*local*) 0 (*local*) 0 (*local*) 1 (*global*)
008: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
00c: 3 (FOO)
Version needs section '.gnu.version_r' contains 2 entries:
Addr: 0x0000000000400508 Offset: 0x000508 Link: 6 (.dynstr)
000000: Version: 1 File: libb.so Cnt: 1
0x0010: Name: FOO Flags: none Version: 3
0x0020: Version: 1 File: libc.so.6 Cnt: 1
0x0030: Name: GLIBC_2.2.5 Flags: none Version: 2
Note that there is no DT_NEEDED entry for libb.so, but the latter is referenced
from .gnu.version_r section.
Older ld versions used to add a DT_NEEDED entry in this case, see
https://sourceware.org/bugzilla/show_bug.cgi?id=15149
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