[Bug other/116936] [UBSAN] gcc/diagnostic.cc: null pointer passed as argument

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116936

--- Comment #2 from Filip Kastl <pheeck at gcc dot gnu.org> ---
To replicate this bug, you can do for example

gcc -x c++-header ./gcc/testsuite/g++.dg/header.C

or

gcc -x c-header ./gcc/testsuite/gcc.dg/header.c

There are many more GCC testsuite testcases that produce this error.  Looks
like the error happens only when one of the input files is a header.