On 07/10/2013 01:24 AM, Eric Botcazou wrote:
The idea behind the existing trick is that the reference is within the bounds
of the base object, i.e. the global offset (offset<<3 + bitpos) is positive,
but the bitpos part is negative, so we rearrange it into ((offset-c>>3)<<3 +
(bitpos+c)). Here the global offset is negative because it has overflowed so
I'm not sure the rearrangement makes any sense.
I thought the idea of the trick was that when offset<<3 is too big, we
can use offset as a byte offset and then use bitpos separately in order
to avoid the overflowing operation. But I guess I was wrong; we end up
with a negative number in the assembly output.
So here's a patch that just complains about the class being too big.
Tested x86_64-pc-linux-gnu, applying to trunk. Joseph, I'm assuming the
change makes sense for C as well; let me know if you disagree.
commit b3639b7c7ebca9ee1e2f1adf1b9a41451cbfbe22
Author: Jason Merrill <ja...@redhat.com>
Date: Fri Jul 12 17:45:59 2013 -0700
PR c++/57793
c/
* c-decl.c (finish_struct): Check for too-large class.
cp/
* class.c (layout_class_type): Check for too-large class.
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 8170a80..f7ae648 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -7210,6 +7210,12 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
layout_type (t);
+ if (TYPE_SIZE_UNIT (t)
+ && TREE_CODE (TYPE_SIZE_UNIT (t)) == INTEGER_CST
+ && !TREE_OVERFLOW (TYPE_SIZE_UNIT (t))
+ && !valid_constant_size_p (TYPE_SIZE_UNIT (t)))
+ error ("type %qT is too large", t);
+
/* Give bit-fields their proper types. */
{
tree *fieldlistp = &fieldlist;
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index e516632..45652a6 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6237,6 +6237,12 @@ layout_class_type (tree t, tree *virtuals_p)
/* Let the back end lay out the type. */
finish_record_layout (rli, /*free_p=*/true);
+ if (TYPE_SIZE_UNIT (t)
+ && TREE_CODE (TYPE_SIZE_UNIT (t)) == INTEGER_CST
+ && !TREE_OVERFLOW (TYPE_SIZE_UNIT (t))
+ && !valid_constant_size_p (TYPE_SIZE_UNIT (t)))
+ error ("type %qT is too large", t);
+
/* Warn about bases that can't be talked about due to ambiguity. */
warn_about_ambiguous_bases (t);
diff --git a/gcc/testsuite/c-c++-common/pr57793.c b/gcc/testsuite/c-c++-common/pr57793.c
new file mode 100644
index 0000000..d66fada
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr57793.c
@@ -0,0 +1,23 @@
+/* PR c++/57793 */
+
+struct A { unsigned a : 1; unsigned b : 1; };
+struct B /* { dg-error "type .B. is too large" "" { target { c++ && ilp32 } } } */
+{
+ unsigned char c[0x40000000];
+ unsigned char d[0x40000ff0];
+ struct A e;
+}; /* { dg-error "type .struct B. is too large" "" { target { c && ilp32 } } } */
+
+void *foo (struct B *p)
+{
+ if (p->e.a)
+ return (void *) 0;
+ p->e.b = 1;
+ return p->c;
+}
+
+void
+bar (struct B *p)
+{
+ foo (p);
+}
