ID: 24174
Comment by: tim at sparkart dot com
Reported By: legion at altlinux dot org
Status: Closed
Bug Type: GD related
Operating System: ALTLinux
PHP Version: 4.3.2
New Comment:
I ran into this same issue and went and spent some time debugging it.
Here is the backtrace:
#0 0x40359f9d in _int_free () from /lib/libc.so.6
#1 0x40358dda in free () from /lib/libc.so.6
#2 0x400c3e3f in gdFree (ptr=0x8224114) at gdhelpers.c:100
#3 0x400bae28 in gdFreeDynamicCtx (ctx=0x8224114) at gd_io_dp.c:154
#4 0x0806dcaa in _php_image_create_from_string (data=0x82105c4,
tn=0x81922e2 "JPEG",
ioctx_func_p=0x806433c <gdImageCreateFromJpegCtx>) at
/usr/local/build/php-4.3.2/ext/gd/gd.c:1286
#5 0x0806de1f in zif_imagecreatefromstring (ht=1,
return_value=0x8215ed4, this_ptr=0x0, return_value_used=1)
at /usr/local/build/php-4.3.2/ext/gd/gd.c:1315
#6 0x08189f24 in execute (op_array=0x8216074) at
/usr/local/build/php-4.3.2/Zend/zend_execute.c:1606
#7 0x0817838c in zend_execute_scripts (type=8, retval=0x0,
file_count=3) at /usr/local/build/php-4.3.2/Zend/zend.c:869
#8 0x081442d3 in php_execute_script (primary_file=0xbffff830) at
/usr/local/build/php-4.3.2/main/main.c:1671
#9 0x081908dc in main (argc=2, argv=0xbffff8e4) at
/usr/local/build/php-4.3.2/sapi/cgi/cgi_main.c:1501
#10 0x402fadc4 in __libc_start_main () from /lib/libc.so.6
It looks like the cause of the seg fault is the GD library (I used
gd-2.0.15gif) trying to free some of the memory that php is using.
Specifically php's pointer to the image data.
So the work around was to null out the data pointer on php's side
before it made its call to GD to free up stuff it was using.
Details:
The call made from php that eventually causes the seg fault is in
ext/gd/gd.c around line 1284 in the _php_image_create_from_string
function:
io_ctx->gd_free(io_ctx);
This calls the gdFreeDynamicCtx function in gd_io_dp.c (line 141 in my
copy).
To null out the data pointer contained under the io_ctx variables to
prevent GD from trying to free the memory I added the following above
the gd_free call:
**((void***)(io_ctx+1)) = NULL;
Its kinda messy since we don't have access to any of the GD structs.
The equivalent code on the GD side of things, for example in the
gdFreeDynamicCtx function, would be something like:
((dynamicPtr*)((dpIOCtx*)ctx)->dp)->data = NULL;
Here is what the whole section of code in ext/gd/gd.c looks like (in my
copy):
...
if (!im) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Passed
data is not in '%s' format", tn);
return NULL;
}
// tp - 7/2/2003 - we don't want gd trying to free() our data
**((void***)(io_ctx+1)) = NULL;
#if HAVE_LIBGD204
io_ctx->gd_free(io_ctx);
#else
io_ctx->free(io_ctx);
#endif
...
PHP's built in Gd library doesn't try to free the PHP's data so this
work around shouldn't effect any of the built in stuff (assuming the
structs have the same layouts).
Previous Comments:
------------------------------------------------------------------------
[2003-06-16 13:33:13] [EMAIL PROTECTED]
Not really, but what do you want us to do? We can't fix segfaults in
3rd-party libraries. Well, we can, we can fix them and redistribute
them, exactly like we are doing. So either use the 3rd-party stuff and
hope you get one which doesn't segfault or use the one we bundle that
we have tested and fixed.
------------------------------------------------------------------------
[2003-06-16 13:25:43] legion at altlinux dot org
This is the official position of mantainers of this module ? You don't
support external GD library and use your own fork. Am i right ?
------------------------------------------------------------------------
[2003-06-16 13:00:15] [EMAIL PROTECTED]
<Then next bug is: i can't use function
imagegif() in your solution. Can i post it ?>
No, this is not a bug. Even Boutell does not support gif export.
I strongly suggest you to use only the bundled GD (and thinking about
alternatives for the gif format), its quality and its integration to
php is really better.
pierre
------------------------------------------------------------------------
[2003-06-16 12:40:21] legion at altlinux dot org
This is not the solution at all. Then next bug is: i can't use
function imagegif() in your solution. Can i post it ?
------------------------------------------------------------------------
[2003-06-16 11:54:26] [EMAIL PROTECTED]
There is the solution then, use the bundled library (which has some
bugs fixed the external one hasn't)
------------------------------------------------------------------------
The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at
http://bugs.php.net/24174
--
Edit this bug report at http://bugs.php.net/?id=24174&edit=1
