[PATCH] posix: Fix wordexp WRDE_APPEND to preserve state on non-NOSPACE errors (BZ 34090, CVE-2026-6368)

[Florian Weimer]

* Adhemerval Zanella:

> diff --git a/posix/tst-wordexp-append.c b/posix/tst-wordexp-append.c
> new file mode 100644
> index 0000000000..6253520c57
> --- /dev/null
> +++ b/posix/tst-wordexp-append.c
> @@ -0,0 +1,307 @@

> +/* Attempt to force realloc to relocate the we_wordv buffer by placing an
> +   allocation right after it.  Returns a pointer that must be freed after
> +   the test.  */
> +static void *
> +place_blocker (void)
> +{
> +  void *p = xmalloc (0x1000);
> +  /* Write to it so the compiler cannot optimize it away and the allocator
> +     actually commits the pages.  */
> +  memset (p, 0x41, 0x1000);
> +  return p;
> +}

Is it possible to replace this with an interposed realloc?  Wouldn't
that result in a much more predictable test?

None of the tests check interaction with WRDE_DOOFFS.

The actual code changes look okay to me.

Thanks,
Florian