find_package(VTK) causes IMPORTED_LOCATION not set for imported target "EXPAT::EXPAT" error in x64-linux

[jasjuang]

Environment

• OS: Ubuntu 20.04
• Compiler: gcc 9.3.0

To Reproduce
Please see below CMakeLists.txt to reproduce the error

set(CMAKE_TOOLCHAIN_FILE $ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)

cmake_minimum_required(VERSION 3.20)

project(example)

find_package(VTK)

add_executable(${PROJECT_NAME} ${PROJECT_SOURCE_DIR}/main.cpp)

target_link_libraries(${PROJECT_NAME} ${VTK_LIBRARIES})

In x64-linux, a simple mkdir build && cd build && cmake .. shows the below error

-- Searching for PEGTL
-- Searching for PEGTL - found target taocpp::pegtl
-- Found LibXml2: /home/jasjuang/vcpkg/installed/x64-linux/lib/libxml2.a (found version "2.9.12") 
-- Configuring done
CMake Error in CMakeLists.txt:
  IMPORTED_LOCATION not set for imported target "EXPAT::EXPAT".


-- Generating done
CMake Generate step failed.  Build files cannot be regenerated correctly.

After some debugging, I realized that if I insert set(CMAKE_BUILD_TYPE "Release") the error will go away, e.g.

set(CMAKE_TOOLCHAIN_FILE $ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)

cmake_minimum_required(VERSION 3.20)

project(example)

set(CMAKE_BUILD_TYPE "Release")

find_package(VTK)

add_executable(${PROJECT_NAME} ${PROJECT_SOURCE_DIR}/main.cpp)

target_link_libraries(${PROJECT_NAME} ${VTK_LIBRARIES})

However, cmake config should not fail even if CMAKE_BUILD_TYPE is not set. Would appreciate if someone can fix this.

[dg0yt]

VTK comes with its own FindEXPAT.cmake. And vcpkg comes with a patch for it. There is one suspicious spot in that patch:

vcpkg/ports/vtk/FindExpat.patch

Lines 11 to 16 in 8275003

	+ if(EXPAT_LIBRARY_RELEASE)
	+ vtk_detect_library_type(expat_library_type
	+ PATH "${EXPAT_LIBRARY_RELEASE}")
	+ elseif(EXPAT_LIBRARY_DEBUG)
	+ vtk_detect_library_type(expat_library_type
	+ PATH "${EXPAT_LIBRARY_RELEASE}")

In the last line, what was meant is probably EXPAT_LIBRARY_DEBUG. EXPAT_LIBRARY_RELEASE is known to resolve to false at this point.

[JackBoosY]

But I can't repro it:

cmake_minimum_required(VERSION 3.10)

project(sample)
find_package(VTK REQUIRED)
add_executable(sample test.cpp)
target_link_libraries(sample PRIVATE ${VTK_LIBRARIES})

root@usrUb:/home/usr/work/test# ./../vcpkg/downloads/tools/cmake-3.20.2-linux/cmake-3.20.2-linux-x86_64/bin/cmake CMakeLists.txt  -DCMAKE_TOOLCHAIN_FILE=/home/usr/work/20237/vcpkg/scripts/buildsystems/vcpkg.cmake
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
CMake Warning (dev) at /home/usr/work/20237/vcpkg/installed/x64-linux/share/zlib/vcpkg-cmake-wrapper.cmake:13 (_find_package):
  Policy CMP0074 is not set: find_package uses <PackageName>_ROOT variables.
  Run "cmake --help-policy CMP0074" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  CMake variable ZLIB_ROOT is set to:

    /home/usr/work/20237/vcpkg/installed/x64-linux

  For compatibility, CMake is ignoring the variable.
Call Stack (most recent call first):
  /home/usr/work/20237/vcpkg/scripts/buildsystems/vcpkg.cmake:740 (include)
  /home/usr/work/20237/vcpkg/installed/x64-linux/share/freetype/vcpkg-cmake-wrapper.cmake:4 (find_package)
  /home/usr/work/20237/vcpkg/scripts/buildsystems/vcpkg.cmake:740 (include)
  /home/usr/work/20237/vcpkg/installed/x64-linux/share/vtk/patches/99/FindX11.cmake:207 (find_package)
  /home/usr/work/20237/vcpkg/scripts/buildsystems/vcpkg.cmake:786 (_find_package)
  /home/usr/work/20237/vcpkg/installed/x64-linux/share/vtk/VTK-vtk-module-find-packages.cmake:162 (find_package)
  /home/usr/work/20237/vcpkg/installed/x64-linux/share/vtk/vtk-config.cmake:136 (include)
  /home/usr/work/20237/vcpkg/scripts/buildsystems/vcpkg.cmake:786 (_find_package)
  CMakeLists.txt:5 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Found ZLIB: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libz.a (found version "1.2.11")
-- Found BZip2: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libbz2.a (found version "1.0.8")
-- Looking for BZ2_bzCompressInit
-- Looking for BZ2_bzCompressInit - found
-- Found PNG: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libpng.a (found version "1.6.37")
-- Found X11: /usr/include
-- Looking for XOpenDisplay in /usr/lib/x86_64-linux-gnu/libX11.so;/usr/lib/x86_64-linux-gnu/libXext.so
-- Looking for XOpenDisplay in /usr/lib/x86_64-linux-gnu/libX11.so;/usr/lib/x86_64-linux-gnu/libXext.so - found
-- Looking for gethostbyname
-- Looking for gethostbyname - found
-- Looking for connect
-- Looking for connect - found
-- Looking for remove
-- Looking for remove - found
-- Looking for shmat
-- Looking for shmat - found
-- Looking for IceConnectionNumber in ICE
-- Looking for IceConnectionNumber in ICE - found
-- Found OpenGL: /usr/lib/x86_64-linux-gnu/libOpenGL.so  found components: OpenGL GLX
-- Found OGG: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libogg.a
-- Found THEORA: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libtheora.a
-- Found NetCDF: /home/usr/work/20237/vcpkg/installed/x64-linux/include (found version "4.7.4")
-- Searching for PEGTL
-- Searching for PEGTL - found target taocpp::pegtl
-- Found JsonCpp: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libjsoncpp.a (found suitable version "1.9.3", minimum required is "0.7.0")
-- Found LibXml2: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libxml2.a (found version "2.9.12")
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - yes
-- Performing Test Iconv_IS_BUILT_IN
-- Performing Test Iconv_IS_BUILT_IN - Success
-- Found Iconv: /usr/lib/x86_64-linux-gnu/libc.so
-- Found LibHaru: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libhpdf.a (found suitable version "2.4.0-dev", minimum required is "2.4.0")
-- Found SQLite3: /home/usr/work/20237/vcpkg/installed/x64-linux/include (found version "3.36.0")
-- Found LibPROJ: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libproj.a (found version "7.2.1")
-- Found Eigen3: /home/usr/work/20237/vcpkg/installed/x64-linux/include/eigen3 (found version "3.3.9")
-- Found EXPAT: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libexpat.a (found version "2.4.1")
-- Found double-conversion: /home/usr/work/20237/vcpkg/installed/x64-linux/debug/lib/libdouble-conversion.a
-- Found LZMA: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/liblzma.a (found version "5.2.5")
-- Found utf8cpp: /home/usr/work/20237/vcpkg/installed/x64-linux/include/utf8cpp
-- Found JPEG: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libjpeg.a (found version "62")
-- Found TIFF: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libtiff.a (found version "4.3.0")
-- Found Freetype: /home/usr/work/20237/vcpkg/installed/x64-linux/lib/libfreetype.a (found version "2.11.0")
-- Configuring done
CMake Warning (dev) in CMakeLists.txt:
  Policy CMP0111 is not set: An imported target missing its location property
  fails during generation.  Run "cmake --help-policy CMP0111" for policy
  details.  Use the cmake_policy command to set the policy and suppress this
  warning.

  IMPORTED_LOCATION not set for imported target "EXPAT::EXPAT".
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Generating done
-- Build files have been written to: /home/usr/work/test
root@usrUb:/home/usr/work/test# make
CMakeFiles/sample.dir/build.make:247: *** target pattern contains no '%'.  Stop.
CMakeFiles/Makefile2:82: recipe for target 'CMakeFiles/sample.dir/all' failed
make[1]: *** [CMakeFiles/sample.dir/all] Error 2
Makefile:90: recipe for target 'all' failed
make: *** [all] Error 2

Oh, it's a warning message in my side.

[JackBoosY]

Okay, the related issues are #19035 #9947.
I wish to fix them completely.

[dg0yt]

The expat wrapper sets IMPORTED_LOCATION_RELEASE and IMPORTED_LOCATION_DEBUG, but not IMPORTED_LOCATION.

Policy CMP0111 is not set

This policy is set as soon as you use cmake_minimum_required(3.19) or higher, and then it will become an error to not have an IMPORTED_LOCATION... matching the CMAKE_BUILD_TYPE. All ports in vcpkg build with either Release or Debug type. But user projects may leave CMAKE_BUILD_TYPE uninitialized. This is what is reported here.
(AFAICT there are some other quirks when you don't set CMAKE_BUILD_TYPE.)

[JackBoosY]

In installed/x64-linux/share/vtk/VTK-vtk-module-find-packages.cmake:
find_package(EXPAT
VTK will call the installed FindEXPAT.cmake first.

Remove the internal FindEXPAT.cmake can fix this issue.

[dg0yt]

VTK will call the installed FindEXPAT.cmake first.

But even then, vcpkg will use the expat wrapper.

[JackBoosY]

@dg0yt vtk will use them both: call vcpkg-cmake-wrapper in share/expat first, then call FindEXPAT.cmake in share/vtk at last.
That because:

vcpkg/ports/expat/vcpkg-cmake-wrapper.cmake

Line 16 in 59a3f35

_find_package(${ARGS})