Re: [PATCH] Initialize the entire obstack struct [BZ #17919]

[Siddhesh Poyarekar]

... 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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