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Bug 1684

Summary: SDL_image fails to load an image with libpng-compat installed
Product: SDL_image Reporter: David North <bigchimp2005>
Component: miscAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: bigchimp2005, yaohan.chen
Version: unspecified   
Hardware: x86_64   
OS: Linux   
Attachments: config.log with both libpng 1.2 and 1.6 installed, default configure options
config.log with both libpng 1.2 and 1.6 installed, --disable-png-shared
config.log with libpng 1.6 installed, and without libpng 1.2 installed

Description David North 2013-01-09 13:38:25 UTC 
Building SDL_image latest (from Mecurial) with libpng-compat installed under Fedora 17 causes PNG files (that worked perfectly well under SDL 1.2) to return NULL.

I am calling the method IMG_LoadTexture, but I believe the actual problem resides in IMG_Load

The error returned is 'undefined symbol: _png_set_longjmp_fn'

libpng-compat is installed with Google Chrome, and so it took a little bit of tracking down in order to find the offending package.

I've fixed it now by removing libpngt-compat and recompiling SDL_image, but if there is any other information you require, please let me know
Comment 1 Sam Lantinga 2013-06-03 01:57:38 UTC 
Can you download the source and send me the output of configure with and without libpng-compat installed?

My guess is that it's finding newer libpng headers, and finding the old png library and using that as the one to load.
Comment 2 Yaohan Chen 2013-06-07 13:13:23 UTC 
Created attachment 1182 [details]
config.log with both libpng 1.2 and 1.6 installed, default configure options
Comment 3 Yaohan Chen 2013-06-07 13:15:34 UTC 
Created attachment 1183 [details]
config.log with both libpng 1.2 and 1.6 installed, --disable-png-shared
Comment 4 Yaohan Chen 2013-06-07 13:17:44 UTC 
Created attachment 1184 [details]
config.log with libpng 1.6 installed, and without libpng 1.2 installed
Comment 5 Yaohan Chen 2013-06-07 13:32:20 UTC 
I also have this problem on Arch Linux. I have the following library files owned by the libpng 1.6 and 1.2 packages:

libpng 1.6
/usr/lib/libpng.so
/usr/lib/libpng16.so
/usr/lib/libpng16.so.16
/usr/lib/libpng16.so.16.2.0

libpng 1.2
/usr/lib/libpng.so.3
/usr/lib/libpng.so.3.50.0
/usr/lib/libpng12.so
/usr/lib/libpng12.so.0
/usr/lib/libpng12.so.0.50.0

With both packages installed, configure will by default generate both -lpng and -lpng.so.3. With both packages installed and --disable-png-shared, configure will generate only -lpng, which produces a working build for me. With libpng 1.2 removed, it also produces a working build.

The problem seems to be due to in lines 218 to 226 of configure.in:
                png_lib=[`find_lib "libpng.so.[0-9]"`]
                if test x$png_lib = x; then
                    png_lib=[`find_lib "libpng.so.[0-9]*"`]
                fi
                if test x$png_lib = x; then
                    png_lib=[`find_lib "libpng*.so.[0-9]"`]
                fi
                if test x$png_lib = x; then
                    png_lib=[`find_lib "libpng*.so.[0-9]*"`]
                fi
This matches libpng.so.3 but not ligpng.so. Maybe this is not even necessary since another part of configure uses pkg-config to get flags for libpng 1.6 correctly.
Comment 6 Sam Lantinga 2013-06-08 00:56:18 UTC 
Okay, this should be fixed.
http://hg.libsdl.org/SDL_image/rev/2608ba5feac1

Please let me know if this doesn't work or breaks something else.

Thanks!