Build failure on GCC 5.2.0

[Earnestly]

• libpng: 1.6.18
• zlib 1.2.8

I am guessing the dependencies based on the linker arguments, if I am missing
any please do mention them:

g++ -std=gnu++11 -DNDEBUG -O3 -g0 -Wall maniac/util.c maniac/chance.cpp image/crc32k.c image/image.cpp image/image-png.cpp image/image-pnm.cpp image/color_range.cpp transform/factory.cpp flif.cpp -lpng -o flif
image/image-png.cpp: In function ‘int image_save_png(const char*, const Image&)’:
image/image-png.cpp:133:37: error: ‘Z_BEST_COMPRESSION’ was not declared in this scope
   png_set_compression_level(png_ptr,Z_BEST_COMPRESSION);
                                     ^
Makefile:2: recipe for target 'flif' failed
make: *** [flif] Error 1

[Earnestly]

Was caused by a missing zlib.h include in image-cpp.h. This was apparently fixed in commit 3efcfce and the build now proceeds. Please consider maybe using pkg-config for the flags such as:

CXXFLAGS := $(shell pkg-config --cflags zlib libpng)
LDFLAGS := $(shell pkg-config --libs zlib libpng)

And then using an appropriate makefile which (re)uses proper rules. Consider this simple example: https://github.com/vodik/envoy/blob/master/Makefile

Also see:

• http://make.mad-scientist.net/papers/rules-of-makefiles/