Re: [PATCH 2/4] Fix gcc-11 compilation warning on symbols.c

[lijiang <lijiang@xxxxxxxxxx>]

Hi, Kazu

Thank  you for the fix.

On Fri, Jul 22, 2022 at 12:45 PM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab@xxxxxxx> wrote:

Without the patch, the following gcc-11 compliation warning is emitted
for symbols.c:

symbols.c: In function 'cmd_p':
symbols.c:7412:38: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 7412 |                         *(cpuspec-1) = ':';
      |                         ~~~~~~~~~~~~~^~~~~

I have one question about it:

This issue only appears in gcc-11 and earlier, I tested it with gcc-12, but it disappeared. It's interesting.

In addition, a new warning was found(gcc-12), but it is not related to this patch.

...

gcc -c -g -DX86_64 -DLZO -DGDB_10_2 -g -O2 lkcd_v1.c -DMCLX -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
lkcd_v1.c: In function ‘dump_lkcd_environment_v1’:
lkcd_v1.c:252:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dh_panic_string’ will never be NULL [-Waddress]
  252 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v1.c:21:
lkcd_vmdump_v1.h:108:30: note: ‘dh_panic_string’ declared here
  108 |         char                 dh_panic_string[DUMP_PANIC_LEN];
      |                              ^~~~~~~~~~~~~~~
gcc -c -g -DX86_64 -DLZO -DGDB_10_2 -g -O2 lkcd_v2_v3.c -DMCLX -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
lkcd_v2_v3.c: In function ‘dump_lkcd_environment_v2_v3’:
lkcd_v2_v3.c:310:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dh_panic_string’ will never be NULL [-Waddress]
  310 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v2_v3.c:21:
lkcd_vmdump_v2_v3.h:205:30: note: ‘dh_panic_string’ declared here
  205 |         char                 dh_panic_string[DUMP_PANIC_LEN];
      |                              ^~~~~~~~~~~~~~~
gcc -c -g -DX86_64 -DLZO -DGDB_10_2 -g -O2 lkcd_v5.c -DMCLX -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
lkcd_v5.c: In function ‘dump_lkcd_environment_v5’:
lkcd_v5.c:273:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dh_panic_string’ will never be NULL [-Waddress]
  273 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v5.c:20:
lkcd_dump_v5.h:163:30: note: ‘dh_panic_string’ declared here
  163 |         char                 dh_panic_string[DUMP_PANIC_LEN];
      |                              ^~~~~~~~~~~~~~~
gcc -c -g -DX86_64 -DLZO -DGDB_10_2 -g -O2 lkcd_v7.c -DMCLX -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
lkcd_v7.c: In function ‘dump_lkcd_environment_v7’:
lkcd_v7.c:350:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dh_panic_string’ will never be NULL [-Waddress]
  350 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v7.c:21:
lkcd_dump_v5.h:163:30: note: ‘dh_panic_string’ declared here
  163 |         char                 dh_panic_string[DUMP_PANIC_LEN];
      |                              ^~~~~~~~~~~~~~~
gcc -c -g -DX86_64 -DLZO -DGDB_10_2 -g -O2 lkcd_v8.c -DMCLX -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
lkcd_v8.c: In function ‘dump_lkcd_environment_v8’:
lkcd_v8.c:546:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dh_panic_string’ will never be NULL [-Waddress]
  546 |                 dh && dh->dh_panic_string &&
      |                    ^~
In file included from lkcd_v8.c:23:
lkcd_dump_v8.h:165:30: note: ‘dh_panic_string’ declared here
  165 |         char                 dh_panic_string[DUMP_PANIC_LEN];

...

Thanks.

Lianbo

 

Signed-off-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
---
 symbols.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/symbols.c b/symbols.c
index bee1faf..42c4eb4 100644
--- a/symbols.c
+++ b/symbols.c
@@ -7351,7 +7351,7 @@ cmd_p(void)
        unsigned radix;
        int do_load_module_filter;
        char buf1[BUFSIZE];
-       char *cpuspec;
+       char *cpuspec, *p;

        do_load_module_filter = radix = 0;

@@ -7386,7 +7386,7 @@ cmd_p(void)
         if (argerrs || !args[optind])
                 cmd_usage(pc->curcmd, SYNOPSIS);

-       cpuspec = strrchr(args[optind], ':');
+       p = cpuspec = strrchr(args[optind], ':');
        if (cpuspec)
                *cpuspec++ = NULLCHAR;

@@ -7409,7 +7409,7 @@ cmd_p(void)
                              sp->name);
                else
                        /* maybe a valid C _expression_ (e.g. ':') */
-                       *(cpuspec-1) = ':';
+                       *p = ':';
        }

        process_gdb_output(concat_args(buf1, 0, TRUE), radix,
--
2.31.1

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