[PATCH] avoid incomplete types in -Warray-bounds (PR 86741)

[PATCH] avoid incomplete types in -Warray-bounds (PR 86741)

[Martin Sebor]

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The enhanced handling of MEM_REFs in -Warray-bounds assumes
the object from whose address an offset is being computed has
a complete type.  Since the size of such objects isn't known,
whether the offset (or index) from its beginning is valid
cannot be reliably determined.  The attached patch avoids
dealing with such objects.

Martin

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PR tree-optimization/86741 - ICE in -Warray-bounds indexing into an object of incomplete type

gcc/ChangeLog:

	PR tree-optimization/86741
	* tree-vrp.c (vrp_prop::check_mem_ref): Avoid incomplete types.

gcc/testsuite/ChangeLog:

	PR tree-optimization/86741
	* gcc.dg/Warray-bounds-33.c: New test.

Index: gcc/testsuite/gcc.dg/Warray-bounds-33.c
===================================================================
--- gcc/testsuite/gcc.dg/Warray-bounds-33.c	(nonexistent)
+++ gcc/testsuite/gcc.dg/Warray-bounds-33.c	(working copy)
@@ -0,0 +1,36 @@
+/* PR tree-optimization/86741 - ICE in -Warray-bounds indexing into
+   an object of incomplete type
+   { dg-do compile }
+   { dg-options "-O2 -Wall" }  */
+
+struct S
+{
+  int s;
+};
+
+void f (void);
+
+void test_void (void)
+{
+  extern void v;
+  struct S *b = (struct S*)&v;
+  if (b->s)
+    f ();
+}
+
+void test_incomplete_enum (void)
+{
+  extern enum E e;
+  struct S *b = (struct S*)&e;
+  if (b->s)
+    f ();
+}
+
+void test_func (void)
+{
+  struct S *b = (struct S*)&f;
+  if (b->s)
+    f ();
+}
+
+/* { dg-prune-output "taking address of expression of type .void." } */
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c	(revision 263072)
+++ gcc/tree-vrp.c	(working copy)
@@ -5048,9 +5048,12 @@ vrp_prop::check_mem_ref (location_t location, tree
      a reference/subscript via a pointer to an object that is not
      an element of an array.  References to members of structs and
      unions are excluded because MEM_REF doesn't make it possible
-     to identify the member where the reference originated.  */
+     to identify the member where the reference originated.
+     Incomplete types are excluded as well because their size is
+     not known.  */
   tree reftype = TREE_TYPE (arg);
   if (POINTER_TYPE_P (reftype)
+      || !COMPLETE_TYPE_P (reftype)
       || RECORD_OR_UNION_TYPE_P (reftype))
     return;
 

Re: [PATCH] avoid incomplete types in -Warray-bounds (PR 86741)

[Richard Biener]

On Mon, Jul 30, 2018 at 10:16 PM Martin Sebor <msebor@gmail.com> wrote:
>
> The enhanced handling of MEM_REFs in -Warray-bounds assumes
> the object from whose address an offset is being computed has
> a complete type.  Since the size of such objects isn't known,
> whether the offset (or index) from its beginning is valid
> cannot be reliably determined.  The attached patch avoids
> dealing with such objects.

Looks ok to deal with the testcase, thus please install.

Richard.




> Martin