[Bug tree-optimization/110579] O2, O1 opmtimizations cause a buffer overflow panic during a strcpy

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110579

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The warning:
In function ‘strcpy’,
    inlined from ‘start_header’ at create.c:695:7:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:79:10: warning:
‘__builtin___strcpy_chk’ writing 8 bytes into a region of size 6
[-Wstringop-overflow=]
   79 |   return __builtin___strcpy_chk (__dest, __src, __glibc_objsize
(__dest));
      |         
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Which comes from:

      strcpy (header->header.magic, "ustar  "); //8


The code is not _FORTIFY_SOURCE=2 safe which requires strcpy to only write
exactly the amount to those fields and not combine character fields as
different.


  char magic[6];
  char version[2];