https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94769
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Stefan Schulze Frielinghaus <stefa...@gcc.gnu.org>: https://gcc.gnu.org/g:27594524d8a93cddb197ad8c9d4075c5870f1473 commit r10-8053-g27594524d8a93cddb197ad8c9d4075c5870f1473 Author: Stefan Schulze Frielinghaus <stefa...@linux.ibm.com> Date: Tue Apr 28 13:14:28 2020 +0200 fortran/io.c: Fix use of uninitialized variable num [PR94769] While bootstrapping GCC on S/390 the following warning occurs: gcc/fortran/io.c: In function 'bool gfc_resolve_dt(gfc_code*, gfc_dt*, locus*)': gcc/fortran/io.c:3857:7: error: 'num' may be used uninitialized in this function [-Werror=maybe-uninitialized] 3857 | if (num == 0) | ^~ gcc/fortran/io.c:3843:11: note: 'num' was declared here 3843 | int num; Since gfc_resolve_dt is a non-static function we cannot assume anything about argument DT. Argument DT gets passed to function check_io_constraints which passes values depending on DT, namely dt->asynchronous->value.character.string to function compare_to_allowed_values as well as argument warn which is true as soon as DT->dterr is true. Thus both arguments depend on DT. If function compare_to_allowed_values is called with dt->asynchronous->value.character.string not being an allowed value, and ALLOWED_F2003 as well as ALLOWED_GNU being NULL (which is the case at the particular call side), and WARN equals true, then the function returns with a non-zero value and leaves num uninitialized which renders the warning true. Initialized num to -1 and added an assert statement. gcc/fortran/ChangeLog: 2020-04-29 Stefan Schulze Frielinghaus <stefa...@linux.ibm.com> PR fortran/94769 * io.c (check_io_constraints): Initialize local variable num to -1 and assert that it receives a meaningful value by function compare_to_allowed_values.
