Windows: Can't link a project to OpenEXR that was built with static zlib

[ignus2]

Branch: master (f04fcdd)

Trying to use a Windows build of OpenEXR built with built-in zlib fails at first with the following error at CMake time:

Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
...
... /openexr/lib/cmake/OpenEXR/OpenEXRConfig.cmake:31 (find_dependency)

This is due to find_dependency(ZLIB REQUIRED) in OpenEXRConfig.cmake:31.
If I manually comment out that line, CMake succeeds, but now I get a linker error:

LINK : fatal error LNK1181: cannot open input file 'zlib_static.lib'

This is due to zlib_static being present in the INTERFACE_LINK_LIBRARIES of OpenEXR::OpenEXR
If I also manually remove zlib_static (from OpenEXRTargets.cmake) then my program all builds and runs fine.

I believe if OpenEXR is built with internal static zlib library, then zlib should not appear as a dependency and neither at the interface link libraries.

[meshula]

Can you provide the command line you are using for the cmake generation step?

[ignus2]

In empty build dir, openexr one level up:

cmake ..\openexr -DCMAKE_INSTALL_PREFIX=..\install
cmake --build . --config Release --target Install

[meshula]

Ok, I removed zlib from my path, and I can reproduce the problem.

CMake Error at cmake/OpenEXRSetup.cmake:241 (add_library):
  add_library cannot create ALIAS target "ZLIB::ZLIB" because target
  "zlib_static" is imported but not globally visible.

Here's a fix, could you try it out?

diff --git a/cmake/OpenEXRSetup.cmake b/cmake/OpenEXRSetup.cmake
index 02dd4c5e..0b1049a9 100644
--- a/cmake/OpenEXRSetup.cmake
+++ b/cmake/OpenEXRSetup.cmake
@@ -228,7 +228,7 @@ if(OPENEXR_FORCE_INTERNAL_ZLIB OR NOT ZLIB_FOUND)
     target_include_directories(zlib_shared INTERFACE "${zlib_INTERNAL_DIR}/include")
   endif()

-  add_library(zlib_static STATIC IMPORTED)
+  add_library(zlib_static STATIC IMPORTED GLOBAL)
   add_dependencies(zlib_static zlib_external)
   set_property(TARGET zlib_static PROPERTY
     IMPORTED_LOCATION "${zlib_INTERNAL_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}${zlibstaticlibname}${CMAKE_STATIC_LIBRARY_SUFFIX}"

[ignus2]

It made no difference (should it have?, did it work for you?), resulting OpenEXRConfig.cmake and OpenEXRTargets.cmake ended up being the same.
However using this change did:

diff --git a/src/lib/OpenEXR/CMakeLists.txt b/src/lib/OpenEXR/CMakeLists.txt
index 64797f67..0775daac 100644
--- a/src/lib/OpenEXR/CMakeLists.txt
+++ b/src/lib/OpenEXR/CMakeLists.txt
@@ -189,5 +189,6 @@ openexr_define_library(OpenEXR
     OpenEXR::Iex
     OpenEXR::IlmThread
     Imath::Imath
+  PRIVATE_DEPS
     ZLIB::ZLIB
   )

But it only removed the zlib_static from the INTERFACE_LINK_LIBRARIES of the OpenEXR::OpenEXR target in OpenEXRTargets.cmake.
The find_dependency(ZLIB REQUIRED) still remained in OpenEXRConfig.cmake, and that also needs to be removed.
Unfortunately this change is not suitable, as it must only be used as a PRIVATE_DEPS if zlib was built internally, not otherwise (I think?).

EDIT:
BTW, I don't get this error at all:

CMake Error at cmake/OpenEXRSetup.cmake:241 (add_library):
  add_library cannot create ALIAS target "ZLIB::ZLIB" because target
  "zlib_static" is imported but not globally visible.

OpenEXR builds fine as it is, it is only when I try to use it that I have the issues.

CMake version I use is 3.18.1.

[ignus2]

It seems you have an older CMake, one before 3.18, which introduced the ALIAS_GLOBAL property, and since it is possible to alias non-global imported targets. https://cmake.org/cmake/help/v3.18/prop_tgt/ALIAS_GLOBAL.html
So that'll fix your issue (either that or the GLOBAL option you mentioned).

But the original issue remains. To clarify the title: I successfully built OpenEXR on Windows using it's internal static zlib. Using this build in my own project fails (as detailed in the original post).

[meshula]

Ok, thanks for the extra investigation. Yes, I built with CMake 3.17. I'll update my cmake and try again.

[Camuvingian]

Hi, I have this same issue. Would it be possible to provide the steps required in order to get this to build please? @meshula did you make any progress with this?

My version of cmake is 3.19.2.