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Date:	Thu, 30 Jun 2011 22:23:10 +0300
Message-ID:	<BANLkTiniQr5TEPpVM4FGP5MdDhvDH1cJOQ@mail.gmail.com>
Subject:	Re: [patch] fix epunzip stric aliasing warnings
From:	Ozkan Sezer <sezeroz AT gmail DOT com>
To:	djgpp-workers AT delorie DOT com
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On Thu, Jun 30, 2011 at 10:09 PM, Juan Manuel Guerrero
<juan DOT guerrero AT gmx DOT de> wrote:
> Am Dienstag, 28. Juni 2011 schrieb Ozkan Sezer:
>> Hi:
>>
>> The attached patch fixes strict aliasing violation warnings in
>> djtar/epunzip.c.  The warnings are only visible when using gcc<=3.3
>> (old but one I do use) but worth fixing, IMO, considering the shape
>> of the code.
>>
>> Regards.
>>
>> --
>> O.S.
>>
>
> I tested the patch submitted by Ozkan Sezer using gcc453b and gcc460b both
> djdev204 versions and it fixes the strict warning issues.  The proposed changes
> look ok to me.  If no one objects in a reasonable period of time I will commit
> the patch below.
>

Just a note:  Replacing (int *) casts onto char buffers by (__dj_int_a *)
is not necessary, as char* is already a may_alias type.

> Regards,
> Juan M. Guerrero
>
>
>
>        * src/utils/djtar/epunzip.c (epunzip_read): Fix strict aaliasing warning.
>        From Ozkan Sezer <sezeroz AT gmail DOT com>
>
>
>
> Index: djgpp/src/utils/djtar/epunzip.c
> ===================================================================
> RCS file: /cvs/djgpp/djgpp/src/utils/djtar/epunzip.c,v
> retrieving revision 1.8
> diff -U 3 -r1.8 epunzip.c
> --- djgpp/src/utils/djtar/epunzip.c     9 Jan 2011 14:19:59 -0000       1.8
> +++ djgpp/src/utils/djtar/epunzip.c     30 Jun 2011 19:08:00 -0000
> @@ -54,30 +54,30 @@
>    * for a one-segment ZIP, but fail on other headers. */
>   while(1)
>     {
> -      int buffer = 0;
> +      char buffer[4];
>
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
>
> -      if(*(__dj_short_a *)&buffer != *(const short *)(const void *)"PK")
> +      if(*(__dj_short_a *)buffer != ('K' << 8) + 'P')
>        break;
>
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
>
> -      if(*(__dj_short_a *)&buffer == *(const short *)(const void *)"\x3\x4")
> +      if(*(__dj_short_a *)buffer == ('\004' << 8) + '\003')
>        {
>          /* local header */
>          at_local_header = 1;
>          break;
>        }
> -      else if(*(__dj_short_a *)&buffer == *(const short *)(const void *)"\x30\x30")
> +      else if(*(__dj_short_a *)buffer == ('0' << 8) + '0')
>        {
>          /* spanning marker, but only one segment
>           * => need to find local header. */
>          continue;
>        }
> -      else if(*(__dj_short_a *)&buffer == *(const short *)(const void *)"\x7\x8")
> +      else if(*(__dj_short_a *)buffer == ('\010' << 8) + '\007')
>        {
>          /* spanning marker, multiple segments. */
>          fprintf(log_out, "%s: spanning is not supported\n", zipfilename);
> @@ -89,7 +89,7 @@
>          /* unknown header */
>          fprintf(log_out,
>                  "%s: don't understand header type 0x%02x%02x\n",
> -                 zipfilename, ((char *)&buffer)[0], ((char *)&buffer)[1]);
> +                 zipfilename, buffer[0], buffer[1]);
>          dont_understand = 1;
>          break;
>        }
> @@ -100,25 +100,26 @@
>
>   if (at_local_header) while(1)
>     {
> -      int buffer, ext_header, timedate, crc, size, length, name_length,
> +      int ext_header, timedate, crc, size, length, name_length,
>        extra_length, should_be_written, count, real_file = 0;
> +      char buffer[4];
>       char filename[2048];
>
>       if (!at_local_header)
>        {
> -         ((char *)&buffer)[0] = (char)get_byte();
> -         ((char *)&buffer)[1] = (char)get_byte();
> +         buffer[0] = (char)get_byte();
> +         buffer[1] = (char)get_byte();
>
> -         if(*(__dj_short_a *)&buffer != *(const short *)(const void *)"PK")
> +         if(*(__dj_short_a *)buffer != ('K' << 8) + 'P')
>            {
>              fprintf(log_out, "%s: invalid zip file structure\n", zipfilename);
>              break;
>            }
>
> -         ((char *)&buffer)[0] = (char)get_byte();
> -         ((char *)&buffer)[1] = (char)get_byte();
> +         buffer[0] = (char)get_byte();
> +         buffer[1] = (char)get_byte();
>
> -         if(*(__dj_short_a *)&buffer != *(const short *)(const void *)"\x3\x4")
> +         if(*(__dj_short_a *)buffer != ('\004' << 8) + '\003')
>            {
>              /* not a local header - all done */
>              break;
> @@ -133,57 +134,57 @@
>       get_byte();
>       get_byte();
>
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
>
> -      if(*(__dj_short_a *)&buffer & CRYFLG)
> +      if(*(__dj_short_a *)buffer & CRYFLG)
>        {
>          fprintf(log_out, "%s has encrypted file(s) - use unzip\n", zipfilename);
>          break;
>        }
> -      ext_header = *(__dj_short_a *)&buffer & EXTFLG ? 1 : 0;
> +      ext_header = *(__dj_short_a *)buffer & EXTFLG ? 1 : 0;
>
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
>
> -      method = *(__dj_short_a *)&buffer;
> +      method = *(__dj_short_a *)buffer;
>       if(method != 8 && method != 0)
>        {
>          fprintf(log_out, "%s has file(s) compressed with unsupported method - use unzip\n", zipfilename);
>          break;
>        }
>
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      ((char *)&buffer)[2] = (char)get_byte();
> -      ((char *)&buffer)[3] = (char)get_byte();
> -      timedate = buffer;
> -
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      ((char *)&buffer)[2] = (char)get_byte();
> -      ((char *)&buffer)[3] = (char)get_byte();
> -      crc = buffer;
> -
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      ((char *)&buffer)[2] = (char)get_byte();
> -      ((char *)&buffer)[3] = (char)get_byte();
> -      size = buffer;
> -
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      ((char *)&buffer)[2] = (char)get_byte();
> -      ((char *)&buffer)[3] = (char)get_byte();
> -      length = buffer;
> -
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      name_length = *(__dj_short_a *)&buffer;
> -
> -      ((char *)&buffer)[0] = (char)get_byte();
> -      ((char *)&buffer)[1] = (char)get_byte();
> -      extra_length = *(__dj_short_a *)&buffer;
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      buffer[2] = (char)get_byte();
> +      buffer[3] = (char)get_byte();
> +      timedate = *(__dj_int_a *)buffer;
> +
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      buffer[2] = (char)get_byte();
> +      buffer[3] = (char)get_byte();
> +      crc = *(__dj_int_a *)buffer;
> +
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      buffer[2] = (char)get_byte();
> +      buffer[3] = (char)get_byte();
> +      size = *(__dj_int_a *)buffer;
> +
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      buffer[2] = (char)get_byte();
> +      buffer[3] = (char)get_byte();
> +      length = *(__dj_int_a *)buffer;
> +
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      name_length = *(__dj_short_a *)buffer;
> +
> +      buffer[0] = (char)get_byte();
> +      buffer[1] = (char)get_byte();
> +      extra_length = *(__dj_short_a *)buffer;
>
>       for(count = 0; count < name_length; count++)
>        {
> @@ -277,34 +278,34 @@
>
>          if(ext_header)
>            {
> -             ((char *)&buffer)[0] = (char)get_byte();
> -             ((char *)&buffer)[1] = (char)get_byte();
> -             ((char *)&buffer)[2] = (char)get_byte();
> -             ((char *)&buffer)[3] = (char)get_byte();
> -             if(buffer != *(int *)"PK\x7\x8")
> +             buffer[0] = (char)get_byte();
> +             buffer[1] = (char)get_byte();
> +             buffer[2] = (char)get_byte();
> +             buffer[3] = (char)get_byte();
> +             if(*(__dj_int_a *)buffer != ('\010' << 24) + ('\007' << 16) + ('K' << 8) + 'P')
>                {
>                  fprintf(log_out, "%s: invalid zip file structure\n",
>                          zipfilename);
>                  break;
>                }
>
> -             ((char *)&buffer)[0] = (char)get_byte();
> -             ((char *)&buffer)[1] = (char)get_byte();
> -             ((char *)&buffer)[2] = (char)get_byte();
> -             ((char *)&buffer)[3] = (char)get_byte();
> -             crc = buffer;
> -
> -             ((char *)&buffer)[0] = (char)get_byte();
> -             ((char *)&buffer)[1] = (char)get_byte();
> -             ((char *)&buffer)[2] = (char)get_byte();
> -             ((char *)&buffer)[3] = (char)get_byte();
> -             size = buffer;
> -
> -             ((char *)&buffer)[0] = (char)get_byte();
> -             ((char *)&buffer)[1] = (char)get_byte();
> -             ((char *)&buffer)[2] = (char)get_byte();
> -             ((char *)&buffer)[3] = (char)get_byte();
> -             length = buffer;
> +             buffer[0] = (char)get_byte();
> +             buffer[1] = (char)get_byte();
> +             buffer[2] = (char)get_byte();
> +             buffer[3] = (char)get_byte();
> +             crc = *(__dj_int_a *)buffer;
> +
> +             buffer[0] = (char)get_byte();
> +             buffer[1] = (char)get_byte();
> +             buffer[2] = (char)get_byte();
> +             buffer[3] = (char)get_byte();
> +             size = *(__dj_int_a *)buffer;
> +
> +             buffer[0] = (char)get_byte();
> +             buffer[1] = (char)get_byte();
> +             buffer[2] = (char)get_byte();
> +             buffer[3] = (char)get_byte();
> +             length = *(__dj_int_a *)buffer;
>            }
>
>        }
>
>

Regards.

--
O.S.

- Raw text -