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malloc: Fix missing accounting of top chunk in malloc_info [BZ #24026]

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Fixes `<total type="rest" size="..."> incorrectly showing as 0 most
of the time.

The rest value being wrong is significant because to compute the
actual amount of memory handed out via malloc, the user must subtract
it from <system type="current" size="...">. That result being wrong
makes investigating memory fragmentation issues like
<https://bugzilla.redhat.com/show_bug.cgi?id=843478> close to
impossible.
This commit is contained in:
Niklas Hambüchen 2019-08-08 22:02:27 +02:00 committed by Florian Weimer
parent a02cd8e4e0
commit b6d2c4475d
2 changed files with 12 additions and 0 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2019-08-08 Niklas Hambüchen <mail@nh2.me>
Carlos O'Donell <carlos@redhat.com>
[BZ #24026]
* malloc/malloc.c (__malloc_info): Account for top chunk.
2019-08-07 Joseph Myers <joseph@codesourcery.com>
* sysdeps/unix/sysv/linux/bits/fcntl-linux.h [__USE_GNU]

6
malloc/malloc.c
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@ -5406,6 +5406,12 @@ __malloc_info (int options, FILE *fp)
__libc_lock_lock (ar_ptr->mutex);
/* Account for top chunk. The top-most available chunk is
treated specially and is never in any bin. See "initial_top"
comments. */
avail = chunksize (ar_ptr->top);
nblocks = 1; /* Top always exists. */
for (size_t i = 0; i < NFASTBINS; ++i)
{
mchunkptr p = fastbin (ar_ptr, i);