[Bug middle-end/86121] [9 Regression] missing -Wstringop-overflow on strcpy followed by strcat

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86121

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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           Keywords|                            |diagnostic

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The problem is due to the MEM_REF that the strcat() call is transformed into. 
Prior to GCC 9 the strcat() call would be transformed to memcpy() like so:

  MEM[(char * {ref-all})&a] = MEM[(char * {ref-all})"12"];
  __builtin_memcpy (&MEM[(void *)&a + 2B], "3", 2); [tail call]

Bisection points to the following commit as the cause of the change:

r261061 | rguenth | 2018-06-01 06:49:54 -0400 (Fri, 01 Jun 2018) | 8 lines

2018-06-01  Richard Biener  <rguenther@suse.de>

        PR middle-end/86017
        * gimple-fold.c (var_decl_component_p): Also allow offsetted
        vars wrapped in MEM_REFs.

        * gcc.dg/tree-ssa/pr86017.c: New testcase.