On Tue, Apr 28, 2020 at 08:27:12PM +0200, Stefan Schulze Frielinghaus wrote:
> On Tue, Apr 28, 2020 at 11:33:31AM +0200, Richard Biener wrote:
> > On Tue, Apr 28, 2020 at 10:03 AM Stefan Schulze Frielinghaus via
> > Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > In function handle_vector_size_attribute local variable nunits is
> > > supposed to be initialized by function type_valid_for_vector_size.
> > > However, in case ARGS is null the function may return with a non-null
> > > value and leave nunits uninitialized. This results in warning/error:
> > >
> > > gcc/poly-int.h: In function 'tree_node*
> > > handle_vector_size_attribute(tree_node**, tree, tree, int, bool*)':
> > > gcc/poly-int.h:330:3: error: 'nunits' may be used uninitialized in this
> > > function [-Werror=maybe-uninitialized]
> > > 330 | ((void) (&(RES).coeffs[0] == (C *) 0), \
> > > | ^
> > > gcc/c-family/c-attribs.c:3695:26: note: 'nunits' was declared here
> > > 3695 | unsigned HOST_WIDE_INT nunits;
> > > |
> > >
> > > This is fixed by also checking whether ARGS is null or not.
> > >
> > > Bootstrapped and regtested on S/390. Ok for master?
> >
> > I think it's better to assert that it is not null for example by adding a
> > nonnull attribute? Can you check if that works? If it doesn't the
> > patch is OK.
>
> Yes, that works, too. Please find an updated version attached. If you
> think it is useful I could also add a gcc_assert (!args) for minimal
> testing.
I guess initializing nunits to zero does not really solve the problem
and while failing to identify all call sides (which isn't future-proof
anyway), I went with adding a checking assert statement. Bootstrapped
and regtested on S/390. Ok for master?
>From e07fe025a710de80cade4ae5c6e4351fbd21b672 Mon Sep 17 00:00:00 2001
From: Stefan Schulze Frielinghaus <stefa...@linux.ibm.com>
Date: Sun, 26 Apr 2020 09:42:29 +0200
Subject: [PATCH] c-attribs.c: Fix warning about use of uninitialized variable
nunits
In function handle_vector_size_attribute local variable nunits is
supposed to be initialized by function type_valid_for_vector_size.
However, in case ARGS is null the function may return with a non-null
value and leave nunits uninitialized. This results in warning/error:
gcc/poly-int.h: In function 'tree_node*
handle_vector_size_attribute(tree_node**, tree, tree, int, bool*)':
gcc/poly-int.h:330:3: error: 'nunits' may be used uninitialized in this
function [-Werror=maybe-uninitialized]
330 | ((void) (&(RES).coeffs[0] == (C *) 0), \
| ^
gcc/c-family/c-attribs.c:3695:26: note: 'nunits' was declared here
3695 | unsigned HOST_WIDE_INT nunits;
|
Added attribute nonnull for argument args in order to silence warning
and added an assert statement in order to check the invariant candidate.
gcc/c-family/ChangeLog:
2020-05-04 Stefan Schulze Frielinghaus <stefa...@linux.ibm.com>
* c-attribs.c (handle_vector_size_attribute): Add attribute
nonnull for argument args in order to silence warning of
uninitialized variable usage and add assert statement in order
to check for invariant candidate.
---
gcc/c-family/c-attribs.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index ac936d5bbbb..dafc77cbcb7 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -117,7 +117,7 @@ static tree handle_tm_attribute (tree *, tree, tree, int,
bool *);
static tree handle_tm_wrap_attribute (tree *, tree, tree, int, bool *);
static tree handle_novops_attribute (tree *, tree, tree, int, bool *);
static tree handle_vector_size_attribute (tree *, tree, tree, int,
- bool *);
+ bool *) ATTRIBUTE_NONNULL(3);
static tree handle_nonnull_attribute (tree *, tree, tree, int, bool *);
static tree handle_nonstring_attribute (tree *, tree, tree, int, bool *);
static tree handle_nothrow_attribute (tree *, tree, tree, int, bool *);
@@ -3697,6 +3697,8 @@ handle_vector_size_attribute (tree *node, tree name, tree
args,
if (!type)
return NULL_TREE;
+ gcc_checking_assert (args != NULL);
+
tree new_type = build_vector_type (type, nunits);
/* Build back pointers if needed. */
--
2.25.3
