On March 21, 2016 6:55:28 PM GMT+01:00, Marek Polacek <pola...@redhat.com>
wrote:
>This PR points out to a GC problem: when we freed a duplicate typedef,
>we were
>leaving its type in the variants list, with its TYPE_NAME still
>pointing to the
>now-freed TYPE_DECL, leading to a crash. I was lucky to discover that
>the
>exact same problem was fixed in November for the C++ FE, so I could
>just follow
>suit here. And because that change didn't add a new testcase, I'm
>putting the
>new test into c-c++-common/.
>
>Bootstrapped/regtested on x86_64-linux, ok for trunk/5?
But IIRC this will drop the aligned attribute effect as that applied to the new
type?
Richard.
>2016-03-21 Marek Polacek <pola...@redhat.com>
>
> PR c/70297
> * c-decl.c (merge_decls): When combining typedefs, remove the new
> type from the variants list.
>
> * c-c++-common/pr70297.c: New test.
>
>diff --git gcc/c/c-decl.c gcc/c/c-decl.c
>index bab4715..98d7f2a 100644
>--- gcc/c/c-decl.c
>+++ gcc/c/c-decl.c
>@@ -2358,6 +2358,26 @@ merge_decls (tree newdecl, tree olddecl, tree
>newtype, tree oldtype)
> DECL_ATTRIBUTES (newdecl)
> = targetm.merge_decl_attributes (olddecl, newdecl);
>
>+ /* For typedefs use the old type, as the new type's DECL_NAME points
>+ at newdecl, which will be ggc_freed. */
>+ if (TREE_CODE (newdecl) == TYPE_DECL)
>+ {
>+ newtype = oldtype;
>+
>+ /* And remove the new type from the variants list. */
>+ if (TYPE_NAME (TREE_TYPE (newdecl)) == newdecl)
>+ {
>+ tree remove = TREE_TYPE (newdecl);
>+ for (tree t = TYPE_MAIN_VARIANT (remove); ;
>+ t = TYPE_NEXT_VARIANT (t))
>+ if (TYPE_NEXT_VARIANT (t) == remove)
>+ {
>+ TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (remove);
>+ break;
>+ }
>+ }
>+ }
>+
> /* Merge the data types specified in the two decls. */
> TREE_TYPE (newdecl)
> = TREE_TYPE (olddecl)
>diff --git gcc/testsuite/c-c++-common/pr70297.c
>gcc/testsuite/c-c++-common/pr70297.c
>index e69de29..bc078c8 100644
>--- gcc/testsuite/c-c++-common/pr70297.c
>+++ gcc/testsuite/c-c++-common/pr70297.c
>@@ -0,0 +1,10 @@
>+/* PR c/70297 */
>+/* { dg-do compile } */
>+/* { dg-options "-g" } */
>+
>+typedef unsigned int uint32_t;
>+typedef uint32_t T;
>+typedef uint32_t T __attribute__((aligned(4)));
>+struct S {
>+ T *t;
>+};
>
> Marek
