Adding zlib-ng as a third-party library

[kbieniex]

I'm trying to replace zlib with zlib-ng, as a third-party library to my project.
In my project's CMakeLists.txt:
add_custom_target(zlib-ng) set(ZLIB_COMPAT ON) add_subdirectory("src/thirdparty/zlib-ng")

But I'm getting an error during building: error: ‘Z_EXTERN’ does not name a type; did you mean ‘ZEXTERN’

Am I missing a step in CMake?

[mtl1979]

add_subdirectory() requires two parameters, so you are missing the second one.

Even though cmake documentation says the second parameter is optional, it only is optional when building in-tree, as when building out of source tree, the path in second parameter is used to find any generated files. The path in second parameter has to be subdirectory of current build directory.

[nmoinvaz]

I have an example on how to do this on the Wiki.

[kbieniex]

I followed the guide "Using zlib-ng with third-party projects in CMake" and my CMakeLists.tx looks like this:
set(ZLIB_COMPAT ON)
add_subdirectory("src/thirdparty/zlib-ng" "src/thirdparty/zlib-ng" EXCLUDE_FROM_ALL)

SET(ZLIB_INCLUDE_DIR ${CMAKE_BINARY_DIR}/zlib-ng CACHE STRING "Path to zlib include directory")
SET(ZLIB_LIBRARY ZLIB:ZLIB CACHE STRING "Path to zlib directory")
include_directories(${ZLIB_INCLUDE_DIR})

add_library(ZLIB:ZLIB ALIAS zlib)

I'm getting an error in one of my .cpp files that includes "zlib.h":
error: ‘Bytef’ was not declared in this scope

[mtl1979]

Byfef type was used in 16-bit processors, it has no use in 32-bit or 64-bit processors.

[kbieniex]

When I change it to Byte, same error. It seams that during build zconf is not seen by the compiler

[mtl1979]

That usually means that the second parameter to add_subdirectory() is not absolute path, it should start with contents of CMAKE_CURRENT_BINARY_DIR.

[kbieniex]

Changed it to "${CMAKE_BINARY_DIR}/src/thirdparty/zlib-ng", but still persists

[mtl1979]

Then you need to check that the include path in generated Makefiles match the location of zconf.h... As long as ZLIB_INCLUDE_DIR is set correctly and used, it should find the file. Looking at the earlier snippet, it is set incorrectly. It needs to include both the source and binary directories.

[kbieniex]

Solved it. include_directories(${ZLIB_SOURCE_DIR}) also needs to be included, because I had a different subproject that had it's own zlib.h

[Shosh18]

I’m trying to do this on my iPad. I’m looking for the old a-library I can’t find it