Avoid .symver on common symbols [BZ #21666]
Commit Message
The .symver directive on common symbol just creates a new common symbol,
not an alias and the newer assembler with the bug fix for
https://sourceware.org/bugzilla/show_bug.cgi?id=21661
will issue an error. Before the fix, we got
$ readelf -sW libc.so | grep "loc[12s]"
5109: 00000000003a0608 8 OBJECT LOCAL DEFAULT 36 loc1
5188: 00000000003a0610 8 OBJECT LOCAL DEFAULT 36 loc2
5455: 00000000003a0618 8 OBJECT LOCAL DEFAULT 36 locs
6575: 00000000003a05f0 8 OBJECT GLOBAL DEFAULT 36 locs@GLIBC_2.2.5
7156: 00000000003a05f8 8 OBJECT GLOBAL DEFAULT 36 loc1@GLIBC_2.2.5
7312: 00000000003a0600 8 OBJECT GLOBAL DEFAULT 36 loc2@GLIBC_2.2.5
in libc.so. The versioned loc1, loc2 and locs have the wrong addresses.
After the fix, we got
$ readelf -sW libc.so | grep "loc[12s]"
6570: 000000000039e3b8 8 OBJECT GLOBAL DEFAULT 34 locs@GLIBC_2.2.5
7151: 000000000039e3c8 8 OBJECT GLOBAL DEFAULT 34 loc1@GLIBC_2.2.5
7307: 000000000039e3c0 8 OBJECT GLOBAL DEFAULT 34 loc2@GLIBC_2.2.5
OK for master?
Thanks.
H.J.
---
[BZ #21666]
* misc/regexp.c: Include <stdlib.h>.
(loc1): Initialized to NULL.
(loc2): Likewise.
(locs): Likewise.
---
misc/regexp.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
Comments
On 06/23/2017 06:11 PM, H.J. Lu wrote:
> +/* Define the variables used for the interface. Avoid .symver on common
> + symbol, which just creates a new common symbol, not an alias. */
> +char *loc1 = NULL;
> +char *loc2 = NULL;
I think __attribute__ ((nocommon)) without the initializer would be more
explicit. We already use that for _res in resolv/res_libc.c.
Does this result in a visible difference for applications? If yes,
please file a bug for this and reference it in the ChangeLog and commit
message.
Why didn't our test suite catch it?
Thanks,
Florian
@@ -29,14 +29,17 @@
#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_23)
-/* Define the variables used for the interface. */
-char *loc1;
-char *loc2;
+#include <stdlib.h> /* Get NULL. */
+
+/* Define the variables used for the interface. Avoid .symver on common
+ symbol, which just creates a new common symbol, not an alias. */
+char *loc1 = NULL;
+char *loc2 = NULL;
compat_symbol (libc, loc1, loc1, GLIBC_2_0);
compat_symbol (libc, loc2, loc2, GLIBC_2_0);
/* Although we do not support the use we define this variable as well. */
-char *locs;
+char *locs = NULL;
compat_symbol (libc, locs, locs, GLIBC_2_0);