https://gcc.gnu.org/g:56c73729c3eab08ca48f366bd435f98457743e45
commit r14-10286-g56c73729c3eab08ca48f366bd435f98457743e45
Author: Jakub Jelinek <ja...@redhat.com>
Date: Thu Jun 6 22:12:11 2024 +0200
c: Fix up pointer types to may_alias structures [PR114493]
The following testcase ICEs in ipa-free-lang, because the
fld_incomplete_type_of
gcc_assert (TYPE_CANONICAL (t2) != t2
&& TYPE_CANONICAL (t2) == TYPE_CANONICAL (TREE_TYPE
(t)));
assertion doesn't hold.
This is because t is a struct S * type which was created while struct S
was still incomplete and without the may_alias attribute (and TYPE_CANONICAL
of a pointer type is a type created with can_alias_all = false argument),
while later on on the struct definition may_alias attribute was used.
fld_incomplete_type_of then creates an incomplete distinct copy of the
structure (but with the original attributes) but pointers created for it
are because of the "may_alias" attribute TYPE_REF_CAN_ALIAS_ALL, including
their TYPE_CANONICAL, because while that is created with !can_alias_all
argument, we later set it because of the "may_alias" attribute on the
to_type.
This doesn't ICE with C++ since PR70512 fix because the C++ FE sets
TYPE_REF_CAN_ALIAS_ALL on all pointer types to the class type (and its
variants) when the may_alias is added.
The following patch does that in the C FE as well.
2024-06-06 Jakub Jelinek <ja...@redhat.com>
PR c/114493
* c-decl.cc (c_fixup_may_alias): New function.
(finish_struct): Call it if "may_alias" attribute is
specified.
* gcc.dg/pr114493-1.c: New test.
* gcc.dg/pr114493-2.c: New test.
(cherry picked from commit d5a3c6d43acb8b2211d9fb59d59482d74c010f01)
Diff:
---
gcc/c/c-decl.cc | 15 +++++++++++++++
gcc/testsuite/gcc.dg/pr114493-1.c | 19 +++++++++++++++++++
gcc/testsuite/gcc.dg/pr114493-2.c | 26 ++++++++++++++++++++++++++
3 files changed, 60 insertions(+)
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 52af8f32998..e63dab49589 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -9393,6 +9393,17 @@ c_update_type_canonical (tree t)
}
}
+/* TYPE is a struct or union that we're applying may_alias to after the body is
+ parsed. Fixup any POINTER_TO types. */
+
+static void
+c_fixup_may_alias (tree type)
+{
+ for (tree t = TYPE_POINTER_TO (type); t; t = TYPE_NEXT_PTR_TO (t))
+ for (tree v = TYPE_MAIN_VARIANT (t); v; v = TYPE_NEXT_VARIANT (v))
+ TYPE_REF_CAN_ALIAS_ALL (v) = true;
+}
+
/* Fill in the fields of a RECORD_TYPE or UNION_TYPE node, T.
LOC is the location of the RECORD_TYPE or UNION_TYPE's definition.
FIELDLIST is a chain of FIELD_DECL nodes for the fields.
@@ -9737,6 +9748,10 @@ finish_struct (location_t loc, tree t, tree fieldlist,
tree attributes,
C_TYPE_BEING_DEFINED (t) = 0;
+ if (lookup_attribute ("may_alias", TYPE_ATTRIBUTES (t)))
+ for (x = TYPE_MAIN_VARIANT (t); x; x = TYPE_NEXT_VARIANT (x))
+ c_fixup_may_alias (x);
+
/* Set type canonical based on equivalence class. */
if (flag_isoc23)
{
diff --git a/gcc/testsuite/gcc.dg/pr114493-1.c
b/gcc/testsuite/gcc.dg/pr114493-1.c
new file mode 100644
index 00000000000..446f33eac3b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr114493-1.c
@@ -0,0 +1,19 @@
+/* PR c/114493 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-O2 -flto" } */
+
+void foo (void);
+struct S;
+struct S bar (struct S **);
+struct S qux (const struct S **);
+
+struct __attribute__((__may_alias__)) S {
+ int s;
+};
+
+struct S
+baz (void)
+{
+ foo ();
+ return (struct S) {};
+}
diff --git a/gcc/testsuite/gcc.dg/pr114493-2.c
b/gcc/testsuite/gcc.dg/pr114493-2.c
new file mode 100644
index 00000000000..1b4a5792dc9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr114493-2.c
@@ -0,0 +1,26 @@
+/* PR c/114493 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-O2 -flto -std=c23" } */
+
+void foo (void);
+struct S;
+struct S bar (struct S **);
+struct S qux (const struct S **);
+
+void
+corge (void)
+{
+ struct S { int s; } s;
+ s.s = 0;
+}
+
+struct __attribute__((__may_alias__)) S {
+ int s;
+};
+
+struct S
+baz (void)
+{
+ foo ();
+ return (struct S) {};
+}
