[PATCH v2] log: Fix result of strstr to 'const char *'

[PATCH v2] log: Fix result of strstr to 'const char *'

[Cédric Le Goater]

Assigning the result of strstr() to a 'char *' is unsafe since
strstr() returns a pointer into the original string which is a
read-only 'const char *' string.

A recent change in glibc 2.42.9000  :

   https://sourceware.org/git/?p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690

breaks compiles, complaining the result of strstr() is not a
'const char *' :

../util/log.c:208:24: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  208 |         char *pidstr = strstr(filename, "%");
      |                        ^~~~~~

Fix that.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20251209150346.650473-1-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 util/log.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/log.c b/util/log.c
index 41f78ce86b2522b8b7072c8b76d8e18603142db6..c44d66b5ce78338cf1b2cd26b7503cb94d4570cb 100644
--- a/util/log.c
+++ b/util/log.c
@@ -203,7 +203,7 @@ static ValidFilenameTemplateResult
 valid_filename_template(const char *filename, bool per_thread, Error **errp)
 {
     if (filename) {
-        char *pidstr = strstr(filename, "%");
+        const char *pidstr = strstr(filename, "%");
 
         if (pidstr) {
             /* We only accept one %d, no other format strings */
-- 
2.52.0

Re: [PATCH v2] log: Fix result of strstr to 'const char *'

[Cédric Le Goater]

On 12/9/25 16:41, Cédric Le Goater wrote:
> Assigning the result of strstr() to a 'char *' is unsafe since
> strstr() returns a pointer into the original string which is a
> read-only 'const char *' string.
> 
> A recent change in glibc 2.42.9000  :
> 
>     https://sourceware.org/git/?p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690
> 
> breaks compiles, complaining the result of strstr() is not a
> 'const char *' :
> 
> ../util/log.c:208:24: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    208 |         char *pidstr = strstr(filename, "%");
>        |                        ^~~~~~

There is much more to fix ... :/

../backends/tpm/tpm_passthrough.c: In function ‘tpm_passthrough_open_sysfs_cancel’:
../backends/tpm/tpm_passthrough.c:226:9: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   226 |     dev = strrchr(tpm_pt->tpm_dev, '/');
--
../tests/vhost-user-bridge.c: In function ‘vubr_parse_host_port’:
../tests/vhost-user-bridge.c:749:15: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   749 |     char *p = strchr(buf, ':');
--
../ui/ui-hmp-cmds.c: In function ‘sendkey_completion’:
../ui/ui-hmp-cmds.c:427:9: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   427 |     sep = strrchr(str, '-');
--
../monitor/hmp.c: In function ‘key_get_info’:
../monitor/hmp.c:589:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   589 |     p = strchr(type, ':');
--
../qga/commands-linux.c: In function ‘build_guest_fsinfo_for_pci_dev’:
../qga/commands-linux.c:409:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   409 |     p = strstr(syspath, "/devices/pci");
       |       ^
../qga/commands-linux.c:440:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   440 |     p = strstr(syspath, "/target");
       |       ^
../qga/commands-linux.c:446:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   446 |     p = strstr(syspath, "/ata");
       |       ^
../qga/commands-linux.c:451:11: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   451 |         p = strstr(syspath, "/host");
--
../qga/commands-linux.c: In function ‘build_guest_fsinfo_for_nonpci_virtio’:
../qga/commands-linux.c:553:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   553 |     p = strstr(syspath, "/target");
--
../qga/commands-linux.c: In function ‘build_guest_fsinfo_for_ccw_dev’:
../qga/commands-linux.c:580:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   580 |     p = strstr(syspath, "/devices/css");
--
../gdbstub/gdbstub.c: In function ‘get_feature_xml’:
../gdbstub/gdbstub.c:365:18: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
   365 |     char *term = strchr(p, ':');
--
../block/vmdk.c: In function ‘vmdk_parse_description’:
../block/vmdk.c:1095:13: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  1095 |     opt_pos = strstr(desc, opt_name);
--
../block/vvfat.c: In function ‘get_basename’:
../block/vvfat.c:1829:22: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  1829 |     char* basename = strrchr(path, '/');