[Bug c++/46078] [4.6 regression] new valgrind warnings when compiling an optimization test case

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46078

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-11-29 
18:04:52 UTC ---
As I said earlier, libcpp warnings aren't actually bugs.
For the zlib warnings, here is a standalone testcase:
#include <zlib.h>
#include <stdlib.h>
#include <string.h>

static void *
lto_zalloc (void *opaque, unsigned items, unsigned size)
{
  void *p = malloc (items * size);
//  memset (p, 0xaa, items * size);
  return p;
}

static void
lto_zfree (void *opaque, void *address)
{
  free (address);
}

/* #define lto_zalloc NULL */
/* #define lto_zfree NULL */

__attribute__((noinline, noclone)) void
lto_end_compression (unsigned char *cursor, size_t remaining)
{
  const size_t outbuf_length = 4096;
  unsigned char *outbuf = (unsigned char *) malloc (outbuf_length);
  z_stream out_stream;
  size_t compressed_bytes = 0;
  int status;

  out_stream.next_out = outbuf;
  out_stream.avail_out = outbuf_length;
  out_stream.next_in = cursor;
  out_stream.avail_in = remaining;
  out_stream.zalloc = lto_zalloc;
  out_stream.zfree = lto_zfree;
  out_stream.opaque = Z_NULL;

  status = deflateInit (&out_stream, Z_DEFAULT_COMPRESSION);
  if (status != Z_OK)
    abort ();

  size_t in_bytes, out_bytes;
  status = deflate (&out_stream, Z_FINISH);
  if (status != Z_STREAM_END)
    abort ();

  in_bytes = remaining - out_stream.avail_in;
  out_bytes = outbuf_length - out_stream.avail_out;

  compressed_bytes += out_bytes;

  cursor += in_bytes;
  remaining -= in_bytes;
  out_stream.next_out = outbuf;
  out_stream.avail_out = outbuf_length;
  out_stream.next_in = cursor;
  out_stream.avail_in = remaining;
  status = deflateEnd (&out_stream);
  if (status != Z_OK)
    abort ();
}

unsigned char blob[1024] = {
1, 0, 0, 0, 10, 0, 0, 0, 0x58, 0, 0, 0, 0, 0, 0, 0,
3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 8, 2, 0, 0,
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0x80, 0, 0, 0xab, 3, 0,
0, 0, 0, 0, 0, 1, 6, 0, 0, 0, 0, 0, 0, 0, 0x78, 0x38,
0x36, 0x2d, 0x36, 0x34, 1, 0, 0, 0, 0, 0x80, 0, 0, 0xef, 3, 0, 0,
0, 0, 0, 0, 1, 7, 0, 0, 0, 0, 0, 0, 0, 0x67, 0x65, 0x6e,
0x65, 0x72, 0x69, 0x63, 1, 0, 0, 0 };

int
main (void)
{
  lto_end_compression (blob, 104);
  return 0;
}

on which valgrind warns when it is linked against gcc's libz.a (but not when
linked against Fedora 14 libz.so).

But
http://zlib.net/zlib_faq.html#faq36
says this is not a bug either.  zlib 1.2.4 nevertheless has some changes in
fill_window etc. which memset the area.