buffer size calculation in gethostby_helper()

buffer size calculation in gethostby_helper()

[Jan Kolar]

Dear Corinna,
Please note that in net.cc, some kind of
               string_size += addrsize_out;
is missing somewhere, which affects a buffer allocation.
See the two locations in diff.
(I do not see well how the two loops (passes) communicate, which might 
well be the origin of the problem.)


The problem was discovered with mplayer with some URLs, with DEBUGGING 
defined.

Best regards
Jan

--------------------------
EXAMPLE
$  mplayer.exe 
'http://www.ceskatelevize.cz/ivysilani/1096898594-udalosti-komentare/211411000370805/'
MPlayer SVN-r32518-snapshot-4.5.1 (C) 2000-2010 MPlayer Team
159 audio & 349 video codecs

Playing 
http://www.ceskatelevize.cz/ivysilani/1096898594-udalosti-komentare/211411000370805/.
Resolving www.ceskatelevize.cz for AF_INET6...

Couldn't resolve name for AF_INET6: www.ceskatelevize.cz
Resolving www.ceskatelevize.cz for AF_INET...
  223037 [main] mplayer 7812 gethostby_helper: Note: JK hopping to fix 
the -4 bug in net.cc saying (if defed DEBUGGING) 'Please debug.'
Connecting to server www.ceskatelevize.cz[212.47.26.209]: 80...

Cache size set to 320 KBytes
Cache fill:  0.00% (0 bytes)
Exiting... (End of file)

------------------------

DIFF
$ cd /usr/src/cygwin-1.7.6-1/winsup/ && diff -up 
../rozbalene-orig-src.tar.bz2/cygwin-1.7.6-1/winsup/cygwin/net.cc 
cygwin/net.cc
--- ../rozbalene-orig-src.tar.bz2/cygwin-1.7.6-1/winsup/cygwin/net.cc    
2010-08-16 15:55:07.000000000 +0200
+++ cygwin/net.cc    2011-08-12 00:07:51.709992400 +0200
@@ -1109,6 +1109,8 @@ gethostby_helper (const char *name, cons
        else if (address_len != namelen1)
          continue;
        address_count++;
+          string_size += addrsize_out; // jk-2011 hope this fixes the 
BUG below
+          system_printf ("Note: JK hopping to fix the -4 bug in net.cc 
saying (if defed DEBUGGING) 'Please debug.' ");
      }
        /* Update the records */
        curptr->type = antype; /* Host byte order */
@@ -1192,7 +1194,7 @@ gethostby_helper (const char *name, cons
            else
          memcpy (string_ptr, curptr->data, addrsize_in);
            string_ptr += addrsize_out;
-          string_size -= addrsize_out;
+          string_size -= addrsize_out; // jk-2011 FIXME BUG:   this 
makes it -4 sometimes - before my fix.
            continue;
          }
  #ifdef DEBUGGING


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Re: buffer size calculation in gethostby_helper()

[Corinna Vinschen]

On Aug 12 03:10, Jan Kolar wrote:
> 
> Dear Corinna,
> Please note that in net.cc, some kind of
>               string_size += addrsize_out;
> is missing somewhere, which affects a buffer allocation.
> See the two locations in diff.
> [...]
> DIFF
> $ cd /usr/src/cygwin-1.7.6-1/winsup/ && diff -up
> ../rozbalene-orig-src.tar.bz2/cygwin-1.7.6-1/winsup/cygwin/net.cc
> cygwin/net.cc
> ---
> ../rozbalene-orig-src.tar.bz2/cygwin-1.7.6-1/winsup/cygwin/net.cc
> 2010-08-16 15:55:07.000000000 +0200
> +++ cygwin/net.cc    2011-08-12 00:07:51.709992400 +0200
> @@ -1109,6 +1109,8 @@ gethostby_helper (const char *name, cons
>        else if (address_len != namelen1)
>          continue;
>        address_count++;
> +          string_size += addrsize_out; // jk-2011 hope this fixes
> the BUG below
> +          system_printf ("Note: JK hopping to fix the -4 bug in
> net.cc saying (if defed DEBUGGING) 'Please debug.' ");
>      }
>        /* Update the records */
>        curptr->type = antype; /* Host byte order */
> @@ -1192,7 +1194,7 @@ gethostby_helper (const char *name, cons
>            else
>          memcpy (string_ptr, curptr->data, addrsize_in);
>            string_ptr += addrsize_out;
> -          string_size -= addrsize_out;
> +          string_size -= addrsize_out; // jk-2011 FIXME BUG:   this
> makes it -4 sometimes - before my fix.
>            continue;
>          }
>  #ifdef DEBUGGING

This looks basically correct to me, but the original code is not
from me.  Pierre, would you mind to have a look?


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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