If QUIET= is omitted or the scalar-logical-expr has the value false:
- if any exception (17) is signaling on that image, the processor shall issue a warning indicating which exceptions are signaling, and this warning shall be on the unit identified by the named constant ERROR_UNIT from the intrinsic module ISO_FORTRAN_ENV (16.10.2.9);
- if a stop code is specified, it is recommended that it be made available by formatted output to the same unit.
That’s about as close as it can be to implying that a character stop code in a STOP statement should be output on ERROR_UNIT without saying it outright.