[Bug sanitizer/104929] New: UBSAN: false positive with sprintf

[jengelh at inai dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104929

            Bug ID: 104929
           Summary: UBSAN: false positive with sprintf
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jengelh at inai dot de
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org
  Target Milestone: ---

// g++ -Wall -fsanitize=undefined -O2 -c t.cpp
#include <cstdio>
size_t fun(char *s)
{
        sprintf(s, " ");
        return __builtin_strlen(s);
}

Observed:
t.cpp: In function ‘size_t fun(char*)’:
t.cpp:5:16: warning: null destination pointer [-Wformat-overflow=]
    5 |         sprintf(s, " ");
//gcc version 11.2.1 20220103 [revision
d4a1d3c4b377f1d4acb34fe1b55b5088a3f293f6] (SUSE Linux), Linux amd64 glibc-2.35

Expected:
Don't warn(?)