header include order

[willie]

I'm moving parts of an older project over to vcpkg, and it uses two pkgs, zlib and cryptopp. Unfortunately, when I try to access zlib's zlib.h, it's pulling in cryptopp's zlib.h instead and they are incompatible, because they are totally different headers.

Before moving to vcpkg fully, I managed this problem by making sure that zlib's headers were included first, but I'm not sure how to tell vcpkg or cmake how to do this.

FWIW, I have both in my vcpkg.json, and I include them in my CMakeLists.txt file like so:

find_package (ZLIB REQUIRED)
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE ZLIB::ZLIB)

...

find_package(cryptopp CONFIG REQUIRED)
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE cryptopp::cryptopp)
get_target_property(INCLUDE_DIRS cryptopp::cryptopp INTERFACE_INCLUDE_DIRECTORIES)
foreach(dir ${INCLUDE_DIRS})
	target_include_directories(${CMAKE_PROJECT_NAME} PRIVATE ${dir}/cryptopp)
endforeach()

Perhaps it's how I'm ensuring that crytopp headers are included? (If I don't do the extra part, it won't find them at all.)

[Osyotr]

My quick search over linux packages revealed that:

1. Some distributions install includes into includes/cryptopp/ (notably RHEL)
2. Some distributions install includes into includes/crypto++/ (notably Debian)
3. None of them provide cmake configs, but all of them provide pkg-config files
4. None of them add cryptopp or crypto++ to the includes directories.

You probably should use #include <cryptopp/*.h> instead of #include <*.h> in your project.

[willie]

You are right. Our historical usage predates the nested include structure, but updating it is probably the best solution.

[willie]

If I change all my cryptopp header references to cryptopp/*, and remove the foreach, etc., then it works, but now a different question: how do you set header include order with cmake? Hmmm.