From 27594524d8a93cddb197ad8c9d4075c5870f1473 Mon Sep 17 00:00:00 2001 From: Stefan Schulze Frielinghaus Date: Tue, 28 Apr 2020 13:14:28 +0200 Subject: [PATCH] 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 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. --- gcc/fortran/ChangeLog | 7 +++++++ gcc/fortran/io.c | 4 +++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog index 1e6b593163d..f245cb4d7c0 100644 --- a/gcc/fortran/ChangeLog +++ b/gcc/fortran/ChangeLog @@ -1,3 +1,10 @@ +2020-04-29 Stefan Schulze Frielinghaus + + 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. + 2020-04-27 Thomas Koenig PR fortran/93956 diff --git a/gcc/fortran/io.c b/gcc/fortran/io.c index e066666e01d..981cf9e88dd 100644 --- a/gcc/fortran/io.c +++ b/gcc/fortran/io.c @@ -3840,7 +3840,7 @@ if (condition) \ if (dt->asynchronous) { - int num; + int num = -1; static const char * asynchronous[] = { "YES", "NO", NULL }; /* Note: gfc_reduce_init_expr reports an error if not init-expr. */ @@ -3853,6 +3853,8 @@ if (condition) \ io_kind_name (k), warn, &dt->asynchronous->where, &num)) return false; + gcc_checking_assert (num != -1); + /* For "YES", mark related symbols as asynchronous. */ if (num == 0) { -- 2.30.2