(Philippe Waroquiers, philippe.waroquiers@skynet.be)
This patch provides three improvements in the way the free list is
handled in memcheck.
First improvement: a new command line option --freelist-big-blocks
(default 1000000) specifies the size of "free list big blocks".
Such big blocks will be put on the free list, but will be re-cycled first
(i.e. in preference to block having a smaller size).
This fixes the bug https://bugs.kde.org/show_bug.cgi?id=250065.
Technically, the freed list is divided in two lists : small
and big blocks. Blocks are first released from the big block list.
Second improvement: the blocks of the freed list are re-cycled before
a new block is malloc-ed, not after a block is freed.
This gives better error messages for dangling pointer errors
when doing many frees without doing malloc between the frees.
(this does not uses more memory).
Third improvement: a block bigger than the free list volume will be
put in the free list (till a malloc is done, so as the needed memory
is not bigger than before) but will be put at the beginning of the
free list, rather than at the end. So, allocating then freeing such a
block does not cause any blocks in the free list to be released.
Results of the improvements above, with the new regression test
memcheck/test/big_blocks_freed_list: with the patch, 7 errors
are detected, 6 are giving the (correct) allocation stack.
Without the patch, only 6 errors are detected, 5 errors without
allocation stack, 1 with a (wrong) allocation stack.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12202
lots of the details changed. Made the following generalisations:
- Recast everything to be entirely terms of bytes, instead of a mixture
of (32-bit) words and bytes. This is a bit easier to understand, and
made the following generalisations possible...
- Almost 64-bit clean; no longer assuming 32-bit words/pointers. Only
(I think) non-64-bit clean part is that VG_(malloc)() et al take an
Int as the size arg, and size_t is 64-bits on 64-bit machines.
- Made the alignment of blocks returned by malloc() et al completely
controlled by a single value, VG_MIN_MALLOC_SZB. (Previously there
were various magic numbers and assumptions about block alignment
scattered throughout.) I tested this, all the regression tests pass
with VG_MIN_MALLOC_SZB of 4, 8, 16, 32, 64. One thing required for
this was to make redzones elastic; the asked-for redzone size is now
the minimum size; it will use bigger ones if necessary to get the
required alignment.
Some other specific changes:
- Made use of types a bit more; ie. actually using the type 'Block',
rather than just having everything as arrays of words, so that should
be a bit safer.
- Removed the a->rz_check field, which was redundant wrt. a->clientmem.
- Fixed up the decision about which list to use so the 4 lists which
weren't ever being used now are -- the problem was that this hasn't
been properly updated when alignment changed from 4 to 8 bytes.
- Added a regression test for memalign() and posix_memalign().
memalign() was aborting if passed a bad alignment argument.
- Added some high-level comments in various places, explaining how the
damn thing works.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2579
