Hi!
DECL_USER_ALIGN bit used to be formerly in tree_decl_common structure
directly, thus the memcpy merge_decls performs used to copy also the
DECL_USER_ALIGN (newdecl) bit to DECL_USER_ALIGN (olddecl). But
it has been moved into tree_base, which is not copied that way.
This means that in C if olddecl has normal alignment and newdecl has bigger
alignment and DECL_USER_ALIGN, it will have the bigger DECL_ALIGN (which
is copied with memcpy), but won't have DECL_USER_ALIGN set, so when we call
relayout_decl on it this DECL_ALIGN is reset back to the smaller value.
Fixed by copying that bit.
After writing a larger testcase for this I've noticed that the C++ FE
has a bug in this too, but the other way around, i.e. if olddecl had
user alignment and newdecl does not, newdecl will not inherit the user
alignment.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-02-09 Jakub Jelinek <ja...@redhat.com>
PR c/52181
* c-decl.c (merge_decls): Copy DECL_USER_ALIGN bit from olddecl to
newdecl.
* decl.c (duplicate_decls): If olddecl has bigger DECL_ALIGN than
newdecl, copy DECL_ALIGN to newdecl and or DECL_USER_ALIGN bits.
* c-c++-common/pr52181.c: New test.
--- gcc/c-decl.c.jj 2012-01-15 20:59:56.000000000 +0100
+++ gcc/c-decl.c 2012-02-09 09:33:35.955067726 +0100
@@ -2449,6 +2449,7 @@ merge_decls (tree newdecl, tree olddecl,
memcpy ((char *) olddecl + sizeof (struct tree_common),
(char *) newdecl + sizeof (struct tree_common),
sizeof (struct tree_decl_common) - sizeof (struct tree_common));
+ DECL_USER_ALIGN (olddecl) = DECL_USER_ALIGN (newdecl);
switch (TREE_CODE (olddecl))
{
case FUNCTION_DECL:
--- gcc/cp/decl.c.jj 2012-01-26 09:22:19.000000000 +0100
+++ gcc/cp/decl.c 2012-02-09 09:56:42.129108618 +0100
@@ -2214,7 +2214,12 @@ duplicate_decls (tree newdecl, tree oldd
SET_DECL_INIT_PRIORITY (olddecl, DECL_INIT_PRIORITY (newdecl));
DECL_HAS_INIT_PRIORITY_P (olddecl) = 1;
}
- /* Likewise for DECL_USER_ALIGN and DECL_PACKED. */
+ /* Likewise for DECL_ALIGN, DECL_USER_ALIGN and DECL_PACKED. */
+ if (DECL_ALIGN (olddecl) > DECL_ALIGN (newdecl))
+ {
+ DECL_ALIGN (newdecl) = DECL_ALIGN (olddecl);
+ DECL_USER_ALIGN (newdecl) |= DECL_USER_ALIGN (olddecl);
+ }
DECL_USER_ALIGN (olddecl) = DECL_USER_ALIGN (newdecl);
if (TREE_CODE (newdecl) == FIELD_DECL)
DECL_PACKED (olddecl) = DECL_PACKED (newdecl);
--- gcc/testsuite/c-c++-common/pr52181.c.jj 2012-02-09 09:36:36.332028377
+0100
+++ gcc/testsuite/c-c++-common/pr52181.c 2012-02-09 09:36:04.000000000
+0100
@@ -0,0 +1,13 @@
+/* PR c/52181 */
+/* { dg-do compile } */
+
+extern const int v1[];
+const int __attribute__((aligned(16))) v1[] = { 1 };
+extern const int __attribute__((aligned(16))) v2[];
+const int v2[] = { 1 };
+extern const int __attribute__((aligned(16))) v3[];
+const int __attribute__((aligned(16))) v3[] = { 1 };
+const int __attribute__((aligned(16))) v4[] = { 1 };
+int test[(__alignof__ (v4) != __alignof__ (v1) /* { dg-bogus "is
negative" } */
+ || __alignof__ (v4) != __alignof__ (v2)
+ || __alignof__ (v4) != __alignof__ (v3)) ? -1 : 0];
Jakub
