https://sourceware.org/bugzilla/show_bug.cgi?id=23268
Bug ID: 23268
Summary: gold doesn't handle symbol versions like BFD ld when
linking executable with both -E and --version-script
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gold
Assignee: ccoutant at gmail dot com
Reporter: mh-sourceware at glandium dot org
CC: ian at airs dot com
Target Milestone: ---
$ cat foo.c
void foo() {}
int main() { return 0; }
$ cat ver
FOO {
global: foo;
};
$ gcc -o foo foo.c -Wl,--version-script,ver -fuse-ld=gold -rdynamic
$ objdump -T foo | grep -e '\b\(main\|foo\)$'
000000000000085a g DF .text 0000000000000007 Base foo
0000000000000861 g DF .text 000000000000000b Base main
The above is actually confusing because of bug 23267.
$ readelf -V foo
Version symbols section '.gnu.version' contains 20 entries:
Addr: 00000000000005dc Offset: 0x0005dc Link: 4 (.dynsym)
000: 0 (*local*) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 0 (*local*)
004: 0 (*local*) 0 (*local*) 1 (*global*) 1 (*global*)
008: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
00c: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
010: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
Version definition section '.gnu.version_d' contains 1 entry:
Addr: 0x0000000000000604 Offset: 0x000604 Link: 5 (.dynstr)
000000: Rev: 1 Flags: none Index: 1 Cnt: 1 Name: FOO
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000620 Offset: 0x000620 Link: 5 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 1
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 2
So the problem here is that both exported symbols end up with the same version,
named FOO.
What BFD ld does is:
$ objdump -T foo | grep -e '\b\(main\|foo\)$'
000000000000084a g DF .text 0000000000000007 FOO foo
0000000000000851 g DF .text 000000000000000b Base main
$ readelf -V foo
Version symbols section '.gnu.version' contains 20 entries:
Addr: 00000000000005ba Offset: 0x0005ba Link: 5 (.dynsym)
000: 0 (*local*) 0 (*local*) 3 (GLIBC_2.2.5) 0 (*local*)
004: 0 (*local*) 3 (GLIBC_2.2.5) 1 (*global*) 1 (*global*)
008: 2 (FOO) 1 (*global*) 1 (*global*) 2 (FOO)
00c: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
010: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
Version definition section '.gnu.version_d' contains 2 entries:
Addr: 0x00000000000005e8 Offset: 0x0005e8 Link: 6 (.dynstr)
000000: Rev: 1 Flags: BASE Index: 1 Cnt: 1 Name: foo
0x001c: Rev: 1 Flags: none Index: 2 Cnt: 1 Name: FOO
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000620 Offset: 0x000620 Link: 6 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 1
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 3
That is, it places main in the Base version, and foo in the FOO version.
Please note that gold actually does that when linking libraries:
$ gcc -shared -o libfoo.so foo.c -Wl,--version-script,ver -fuse-ld=gold
$ objdump -T libfoo.so | grep -e '\b\(main\|foo\)$'
000000000000069a g DF .text 0000000000000007 FOO foo
00000000000006a1 g DF .text 000000000000000b Base main
And more than skipping the base version, it actually attributes all symbols to
the first version in executables:
$ cat ver2
FOO {
global: foo;
};
BAR {
global: main;
};
$ gcc -o foo foo.c -Wl,--version-script,ver2 -fuse-ld=gold -rdynamic
$ LANG=C objdump -T foo | grep -e '\b\(main\|foo\)$'
000000000000089a g DF .text 0000000000000007 Base foo
00000000000008a1 g DF .text 000000000000000b Base main
$ readelf -V foo
Version symbols section '.gnu.version' contains 21 entries:
Addr: 00000000000005f8 Offset: 0x0005f8 Link: 4 (.dynsym)
000: 0 (*local*) 3 (GLIBC_2.2.5) 3 (GLIBC_2.2.5) 0 (*local*)
004: 0 (*local*) 0 (*local*) 1 (*global*) 1 (*global*)
008: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
00c: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
010: 1 (*global*) 1 (*global*) 1 (*global*) 1 (*global*)
014: 1 (*global*)
Version definition section '.gnu.version_d' contains 2 entries:
Addr: 0x0000000000000624 Offset: 0x000624 Link: 5 (.dynstr)
000000: Rev: 1 Flags: none Index: 1 Cnt: 1 Name: FOO
0x001c: Rev: 1 Flags: none Index: 2 Cnt: 1 Name: BAR
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x000000000000065c Offset: 0x00065c Link: 5 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 1
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 3
Here, main is not even associated to version BAR.
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