Hi Tobias,
On Tue, Apr 28, 2020 at 05:06:15PM +0200, Tobias Burnus wrote:
> Hi Stefan,
>
> I prefer Jakub's suggestion – his change LGTM.
Please find attached an updated patch. Bootstrapped and regtested on
S/390. Ok for master?
Cheers,
Stefan
> On 4/28/20 2:30 PM, Jakub Jelinek via Gcc-patches wrote:
> > On Tue, Apr 28, 2020 at 01:53:07PM +0200, Stefan Schulze Frielinghaus via
> > Gcc-patches wrote:
> > > gcc/fortran/ChangeLog:
> > >
> > > 2020-04-28 Stefan Schulze Frielinghaus <stefa...@linux.ibm.com>
> > >
> > > PR fortran/94769
> > > * io.c (check_io_constraints): Initialize local variable num.
> > > ---
> > > gcc/fortran/io.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/gcc/fortran/io.c b/gcc/fortran/io.c
> > > index e066666e01d..4526f729d1d 100644
> > > --- a/gcc/fortran/io.c
> > > +++ b/gcc/fortran/io.c
> > > @@ -3840,7 +3840,7 @@ if (condition) \
> > >
> > > if (dt->asynchronous)
> > > {
> > > - int num;
> > > + int num = 2;
> > > static const char * asynchronous[] = { "YES", "NO", NULL };
> > Just nitpicking, wouldn't -1 be more usual value?
> > And, I think there should be an assertion that it didn't remain -1 after the
> > call, above
> > /* For "YES", mark related symbols as asynchronous. */
> > do
> > gcc_checking (num != -1);
> > or so.
> >
> > Note, the reason why this triggers only on s390x is the vastly different
> > inlining parameters the target uses, that causes a lot of headaches
> > everywhere.
> >
> > Jakub
> >
> -----------------
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> Alexander Walter
>From 6118c522e96b978a2a8ba5df5fd90f7b38176e16 Mon Sep 17 00:00:00 2001
From: Stefan Schulze Frielinghaus <stefa...@linux.ibm.com>
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:
2020-04-28 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.
---
gcc/fortran/io.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
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)
{
--
2.25.3
