On Mon, 26 Jun 2006, Eric Botcazou wrote:
> > Reverting your patch makes it go away too. I'll try and look into it
> > tomorrow.
>
> tree
> build_string (int len, const char *str)
> {
> tree s;
> size_t length;
>
> length = len + sizeof (struct tree_string);
>
> s = ggc_alloc_tree (length);
>
> Breakpoint 5, build_string (len=34,
> str=0x1048e58 "No space for profiling buffer(s)\n")
> at /home/eric/svn/gcc/gcc/tree.c:1124
> 1124 length = len + sizeof (struct tree_string);
> (gdb) next
> 1131 s = ggc_alloc_tree (length);
> (gdb) p length
> $1 = 58
> (gdb) next
> 1133 memset (s, 0, sizeof (struct tree_common));
> (gdb) p s
> $2 = 0xff3803fc
>
> 's' should be 8-byte aligned because it's a "tree".
The way it works is that ggc_alloc_stat is asked for 58 bytes, which
if being a correct C object size, has alignof (object) == 2. Now, with
struct tree_string GTY(())
{
struct tree_common common;
int length;
char str[1];
};
it is unfortunate that we compute the allocation size by doing magic
arithmetic instead of asking for sizeof (struct
tree_string_with_length_FOO) (maybe one can do this with some VLA
type?!).
At least I know what's going on, and given stage3 and yadayada it might
be best to revert the non-bugfixing parts of the patch. Or adjust
all ggc_alloc callers to request properly aligned storage... e.g. for
this particular case
Index: tree.c
===================================================================
--- tree.c (revision 115006)
+++ tree.c (working copy)
@@ -1121,7 +1121,8 @@ build_string (int len, const char *str)
tree s;
size_t length;
- length = len + sizeof (struct tree_string);
+ length = (len + sizeof (struct tree_string)
+ + __alignof__ (struct tree_string)) & ~__alignof__ (struct
tree_string);
#ifdef GATHER_STATISTICS
tree_node_counts[(int) c_kind]++;
but with this things going on, the whole reasoning why the patch is
correct falls apart (if we declare doing so correct).
Thanks for tracking this down (and I wonder why ia64 bootstrap succeeded
with trapping misaligned),
Richard.
--
Richard Guenther <[EMAIL PROTECTED]>
Novell / SUSE Labs
