So, annoyingly, I got this wrong.
Bootstrapped and regression tested on x86_64.
Best,
Martin
c23: fix TBAA error for function returning structure [PR125252]
To fix PR122572 we globbed pointers to structure or union types nested
within other structure or union types to a void pointer when computing
the TYPE_CANONICAL. But when doing this for function return types this
then leads to wrong aliasing decisions, because for some reason function
derivation behaves differently than pointer and array derivation. Instead
of globbing to void, replace the nested structure or union type with an
incomplete type instead.
PR c/124252
gcc/c/ChangeLog:
* c-typeck.cc (ptr_to_tagged_member): Return type of member.
(c_type_canonical): Use incomplete type.
gcc/testsuite/ChangeLog:
* gcc.dg/pr125252.c
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 6195d179543..3ffeed73d8c 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -579,8 +579,9 @@ c_reconstruct_complex_type (tree type, tree bottom)
/* Helper function for c_canonical_type. Check whether FIELD
contains a pointer to a structure or union with tag,
- possibly nested in other type derivations. */
-static bool
+ possibly nested in other type derivations, and return the
+ type of this nested structure or union. */
+static tree
ptr_to_tagged_member (tree field)
{
gcc_assert (FIELD_DECL == TREE_CODE (field));
@@ -598,17 +599,17 @@ ptr_to_tagged_member (tree field)
if (ptr_seen
&& RECORD_OR_UNION_TYPE_P (type)
&& NULL_TREE != c_type_tag (type))
- return true;
+ return type;
- return false;
+ return NULL_TREE;
}
/* For a record or union type, make necessary adaptations so that the
type can be used as TYPE_CANONICAL.
If the TYPE contains a pointer (possibly nested in other type
- derivations) to a structure or union as a member, create a copy
- and change such pointers to void pointers. Otherwise, the middle-end
+ derivations) to a structure or union as a member, create a copy and
+ change the nested type to an incomplete type. Otherwise, the middle-end
gets confused when recording component aliases in the case where we
have formed equivalency classes that include types for which these
member pointers end up pointing to other structure or unions types
@@ -635,9 +636,15 @@ c_type_canonical (tree type)
for (tree x = TYPE_FIELDS (type); x; x = DECL_CHAIN (x))
{
tree f = copy_node (x);
- if (ptr_to_tagged_member (x))
- TREE_TYPE (f) = c_reconstruct_complex_type (TREE_TYPE (x),
- ptr_type_node);
+ if (tree m = ptr_to_tagged_member (x))
+ {
+ tree new_node = make_node (TREE_CODE (m));
+ TYPE_NAME (new_node) = TYPE_NAME (m);
+ SET_TYPE_STRUCTURAL_EQUALITY (new_node);
+ new_node = qualify_type (new_node, m);
+ TREE_TYPE (f) = c_reconstruct_complex_type (TREE_TYPE (x),
+ new_node);
+ }
*fields = f;
fields = &DECL_CHAIN (f);
}
diff --git a/gcc/testsuite/gcc.dg/pr125252.c b/gcc/testsuite/gcc.dg/pr125252.c
new file mode 100644
index 00000000000..4e27fa15978
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr125252.c
@@ -0,0 +1,36 @@
+/* { dg-do run } */
+/* { dg-options "-std=gnu23 -O2" } */
+
+
+int k;
+struct S {};
+
+#define T struct S
+
+T *get_sender () {
+ k = 1;
+ return (void *)0;
+}
+
+T *get_cc () { }
+
+void test () {
+ struct {
+ T *(*get_header) (void);
+ } reply_to_map[] = {
+ { get_sender },
+ { get_cc },
+ };
+
+ for (int i = 0; i < 2; i++) {
+ asm ("" ::"r"(reply_to_map[i].get_header ()));
+ }
+}
+
+int main() {
+ test ();
+
+ if (k != 1)
+ __builtin_abort();
+}
+
