[Bug tree-optimization/83733] -Wformat-overflow false positive for %d on bounded integer when inlining

[tim.vanholder at anubex dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83733

--- Comment #2 from Tim Van Holder <tim.vanholder at anubex dot com> ---
Created attachment 43062
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43062&action=edit
Testcase

Testcase attached.

Compiling with "gcc -c -Wall -Wextra -Werror -O3 gcc83733.c" yields:

gcc83733.c: In function ‘caller1’:
gcc83733.c:33:44: error: ‘%02d’ directive writing between 2 and 6 bytes into a
region of size 4 [-Werror=format-overflow=]
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
                                            ^~~~
gcc83733.c:33:38: note: directive argument in the range [-32768, 32767]
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
                                      ^~~~~~~~~~~
gcc83733.c:33:7: note: ‘sprintf’ output between 8 and 12 bytes into a
destination of size 9
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
gcc83733.c: In function ‘caller2’:
gcc83733.c:33:44: error: ‘%02d’ directive writing between 2 and 6 bytes into a
region of size 4 [-Werror=format-overflow=]
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
                                            ^~~~
gcc83733.c:33:38: note: directive argument in the range [-32768, 32767]
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
                                      ^~~~~~~~~~~
gcc83733.c:33:7: note: ‘sprintf’ output between 8 and 12 bytes into a
destination of size 9
       sprintf (r->definition.ddname, "CMPRT%02d", foo);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


There seem to be several subtleties involved.
For example, dropping the 'definition' struct (making 'ddname' a field directly
in 'foo_t') changes the diagnostic, claiming there's 11 bytes in the target
(slack space in the struct?).