Description:
------------
From the libpng README at ftp://ftp.simplesystems.org/pub/libpng/png/src/libpng-1.4.0-README.txt :
"Removed the deprecated png_check_sig() function/macro."

The file ext/gd/libgd/gd_png.c currently uses this function and so will not compile against libpng 1.4.0.  The libpng man page notes the following:

"The function
    png_check_sig(sig, num) was replaced with
    !png_sig_cmp(sig, 0, num) It has been deprecated since libpng-0.90."

I made the following change in gd_png.c and php compiled successfully.


--- ext/gd/libgd/gd_png.c.bad     2010-01-12 16:16:18.000000000 -0600
+++ ext/gd/libgd/gd_png.c 2010-01-12 16:16:55.000000000 -0600
@@ -145,7 +145,7 @@
                return NULL;
        }
 
-       if (!png_check_sig (sig, 8)) { /* bad signature */
+       if (png_sig_cmp (sig, 0, 8)) { /* bad signature */
                return NULL;
        }
 


Reproduce code:
---------------
Compile PHP with --with-gd and --with-libpng-dir pointing to a libpng-1.4.0 install.

Expected result:
----------------
PHP should compile without error.

Actual result:
--------------
ext/gd/libgd/.libs/gd_png.o: In function `php_gd_gdImageCreateFromPngCtx':
....../php-5.3.1/ext/gd/libgd/gd_png.c:148: undefined reference to `png_check_sig'
collect2: ld returned 1 exit status
make: *** [sapi/cli/php] Error 1