... and I forgot to add bug-gnulib to cc before I hit send. Siddhesh
On Tue, Feb 03, 2015 at 08:26:49PM +0530, Siddhesh Poyarekar wrote:
> Hi,
>
> obstack_init does not completely initialize the obstack structure; it
> leaves out the padding bits and valgrind complains about it on s390x:
>
> ==15793== Memcheck, a memory error detector
> ==15793== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
> ==15793== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
> ==15793== Command: /root/obstack
> ==15793==
> ==15793== Conditional jump or move depends on uninitialised value(s)
> ==15793== at 0x403E48CA4E: obstack_free (in /lib64/libc-2.12.so)
> ==15793== by 0x8000072D: main (obstack.c:12)
> ==15793==
> ==15793==
> ==15793== HEAP SUMMARY:
> ==15793== in use at exit: 0 bytes in 0 blocks
> ==15793== total heap usage: 1 allocs, 1 frees, 4,064 bytes allocated
> ==15793==
> ==15793== All heap blocks were freed -- no leaks are possible
> ==15793==
> ==15793== For counts of detected and suppressed errors, rerun with: -v
> ==15793== Use --track-origins=yes to see where uninitialised values come from
> ==15793== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)
>
>
> The fix below (against gnulib, but is identical for glibc) initializes
> all of the obstack struct at once. Verified that the valgrind warning
> is fixed. OK for 2.22 and gnulib?
>
> Siddhesh
>
> ChangeLog for gnulib:
>
> obstack: Initialize whole obstack structure.
> * lib/obstack.c (_obstack_begin): Initialize all of H.
>
> ChangeLog for glibc:
>
> [BZ #17919]
> * malloc/obstack.c (_obstack_begin): Initialize all of H.
>
> diff --git a/malloc/obstack.c b/malloc/obstack.c
> index 5bb3f0d..c1d6ded 100644
> --- a/lib/obstack.c
> +++ b/lib/obstack.c
> @@ -148,6 +148,8 @@ _obstack_begin (struct obstack *h,
> {
> struct _obstack_chunk *chunk; /* points to new chunk */
>
> + memset (h, 0, sizeof (struct obstack));
> +
> if (alignment == 0)
> alignment = DEFAULT_ALIGNMENT;
> if (size == 0)
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