[Bug 2013140] [NEW] -Werror=stringop-overflow -O3 returns false-positives on ppc64el

[Steve Langasek]

Public bug reported:

I have seen various ppc64el-specific build failures in lunar because of
use of -Werror + -O3 and -Wstringop-overflow returing false positive
results.  E.g.:


[...]
mme_context.c: In function ‘mme_context_parse_config’:
mme_context.c:1237:66: error: writing 16 bytes into a region of size 5 [-Werror=stringop-overflow=]
 1237 |                                 network_full_name->name[(i*2)+1] =
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
 1238 |                                     c_network_name[i];
      |                                     ~~~~~~~~~~~~~~~~~             
mme_context.c:29:22: note: at offset 804187 into destination object ‘self’ of size 804192
   29 | static mme_context_t self;
      |                      ^~~~
mme_context.c:1237:66: error: writing 16 bytes into a region of size 0 [-Werror=stringop-overflow=]
 1237 |                                 network_full_name->name[(i*2)+1] =
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
 1238 |                                     c_network_name[i];
      |                                     ~~~~~~~~~~~~~~~~~             
mme_context.c:29:22: note: at offset 804203 into destination object ‘self’ of size 804192
   29 | static mme_context_t self;
      |                      ^~~~
[...]

https://launchpad.net/ubuntu/+source/nextepc/0.3.10+nods-4.2/+build/24633802

There is no object of size 804192 here and these offsets appear to be
fabricated out of whole cloth.

** Affects: gcc-12 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2013140

Title:
  -Werror=stringop-overflow -O3 returns false-positives on ppc64el

Status in gcc-12 package in Ubuntu:
  New

Bug description:
  I have seen various ppc64el-specific build failures in lunar because
  of use of -Werror + -O3 and -Wstringop-overflow returing false
  positive results.  E.g.:

  
  [...]
  mme_context.c: In function ‘mme_context_parse_config’:
  mme_context.c:1237:66: error: writing 16 bytes into a region of size 5 [-Werror=stringop-overflow=]
   1237 |                                 network_full_name->name[(i*2)+1] =
        |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
   1238 |                                     c_network_name[i];
        |                                     ~~~~~~~~~~~~~~~~~             
  mme_context.c:29:22: note: at offset 804187 into destination object ‘self’ of size 804192
     29 | static mme_context_t self;
        |                      ^~~~
  mme_context.c:1237:66: error: writing 16 bytes into a region of size 0 [-Werror=stringop-overflow=]
   1237 |                                 network_full_name->name[(i*2)+1] =
        |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
   1238 |                                     c_network_name[i];
        |                                     ~~~~~~~~~~~~~~~~~             
  mme_context.c:29:22: note: at offset 804203 into destination object ‘self’ of size 804192
     29 | static mme_context_t self;
        |                      ^~~~
  [...]

  https://launchpad.net/ubuntu/+source/nextepc/0.3.10+nods-4.2/+build/24633802

  There is no object of size 804192 here and these offsets appear to be
  fabricated out of whole cloth.

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