| Message ID | 61212D56-5FE8-4496-BC6E-19920F55236E@comcast.net |
|---|---|
| State | New |
| Headers | show |
On 11/13/14 12:37, Mike Stump wrote: > I was doing a merge, and it failed to even compile the runtime > libraries due to checking in bitmap. bitmap goes to remove set bits > from the bitmap (the second hunk in a two hunk set), and it fails to > update the current pointer. That memory is freed and then > reallocated and a new index is put into it, and then we fail a > consistency check later on due to the mismatch between head->index > and head->current->indx, because current was not properly maintained. > This patch removes the old value of current when we remove what it > points to from the bitmap. Was the calling code iterating through the bit with a form like EXECUTE_IF_SET_IN_BITMAP (something, 0, i, bi) { bitmap_clear_bit (something, i) [ ... whatever code we want to process i, ... ] } If so, that's the real issue and we'd really like to identify & fix any code that has that kind of structure. See: https://gcc.gnu.org/ml/gcc/2009-06/msg00482.html jeff
On Fri, Nov 14, 2014 at 2:10 AM, Jeff Law <law@redhat.com> wrote: > On 11/13/14 12:37, Mike Stump wrote: >> >> I was doing a merge, and it failed to even compile the runtime >> libraries due to checking in bitmap. bitmap goes to remove set bits >> from the bitmap (the second hunk in a two hunk set), and it fails to >> update the current pointer. That memory is freed and then >> reallocated and a new index is put into it, and then we fail a >> consistency check later on due to the mismatch between head->index >> and head->current->indx, because current was not properly maintained. >> This patch removes the old value of current when we remove what it >> points to from the bitmap. > > Was the calling code iterating through the bit with a form like > > EXECUTE_IF_SET_IN_BITMAP (something, 0, i, bi) > { > bitmap_clear_bit (something, i) > [ ... whatever code we want to process i, ... ] > } > > If so, that's the real issue and we'd really like to identify & fix any code > that has that kind of structure. > > See: > > https://gcc.gnu.org/ml/gcc/2009-06/msg00482.html Indeed. I can't see how this can have triggered: prev = elt->prev; if (prev) { prev->next = NULL; if (head->current->indx > prev->indx) { head->current = prev; head->indx = prev->indx; so if there was elt->prev then if current == elt current->indx should better be > prev->indx. Sth else must be wrong (and I doubt it's the above bogus use of bitmaps). Richard. > jeff
diff --git a/gcc/bitmap.c b/gcc/bitmap.c index 8f7f306..844c32e 100644 --- a/gcc/bitmap.c +++ b/gcc/bitmap.c @@ -278,7 +296,8 @@ bitmap_elt_clear_from (bitmap head, bitmap_element *elt) if (prev) { prev->next = NULL; - if (head->current->indx > prev->indx) + if (head->current->indx > prev->indx + || head->current == elt) { head->current = prev; head->indx = prev->indx;