https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93733
jvdelisle at charter dot net changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jvdelisle at charter dot net --- Comment #10 from jvdelisle at charter dot net --- There are two levels of checking, compile time and run time. Compile time, if the string is known/constant in gcc/fortran/format.c (IIRC). Runtime is libgfortran parse_format_string or similar. The -std=xxx routines are always a little different betwen implementation in compile time and run-time. Honestly, every time I do these checks I have to try combination to find the right one. Hope this helps a little. If you get stuck, let me know and I will try to take a closer look.