[CMake] Include directories problem when cross compiling with MinGW

[David Demelier]

Hello,

I'm trying to cross compile a project on Arch Linux using MinGW for
Windows.

I've installed a lot of libraries from their AUR into /usr/x86_64-w64-
mingw32. This seems okay as CMake finds every library needed.

My example project consists of:

cmake_minimum_required(VERSION 3.5)
project(test)
find_package(PNG REQUIRED)
add_executable(main main.cpp)
target_link_libraries(main PNG::PNG)

The main.cpp only contains an #include <cstdlib> statement.

The toolchain file contains:

set (CMAKE_SYSTEM_NAME Windows)
set (CMAKE_C_COMPILER x86_64-w64-mingw32-gcc)
set (CMAKE_CXX_COMPILER x86_64-w64-mingw32-g++)
set (CMAKE_FIND_ROOT_PATH /usr/x86_64-w64-mingw32)
set (CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set (CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set (CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set (CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
set (QT_BINARY_DIR /usr/x86_64-w64-mingw32/bin /usr/bin)
set (QT_INCLUDE_DIRS_NO_SYSTEM ON)
set (CMAKE_RC_COMPILER x86_64-w64-mingw32-windres)
set (CMAKE_MC_COMPILER x86_64-w64-mingw32-windmc)
set (Boost_THREADAPI win32)
set (CMAKE_Fortran_COMPILER x86_64-w64-mingw32-gfortran)
set (CMAKE_AR:FILEPATH x86_64-w64-mingw32-ar)
set (CMAKE_RANLIB:FILEPATH x86_64-w64-mingw32-ranlib)

Then, running CMake with that toolchain produce:

$ cmake -DCMAKE_TOOLCHAIN_FILE=/usr/share/mingw/toolchain-x86_64-w64-
mingw32.cmake ..
-- The C compiler identification is GNU 6.1.1
-- The CXX compiler identification is GNU 6.1.1
-- Check for working C compiler: /usr/bin/x86_64-w64-mingw32-gcc
-- Check for working C compiler: /usr/bin/x86_64-w64-mingw32-gcc --
works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/x86_64-w64-mingw32-g++
-- Check for working CXX compiler: /usr/bin/x86_64-w64-mingw32-g++ --
works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found ZLIB: /usr/x86_64-w64-mingw32/lib/libz.dll.a (found version
"1.2.8") 
-- Found PNG: /usr/x86_64-w64-mingw32/lib/libpng.dll.a (found version
"1.6.24") 
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/test/build

So as you can see, the libraries are correctly found. However, compile
fails with:

$ make
Scanning dependencies of target main
[ 50%] Building CXX object CMakeFiles/main.dir/main.cpp.obj
In file included from /tmp/test/main.cpp:1:0:
/usr/x86_64-w64-mingw32/include/c++/6.1.1/cstdlib:75:25: fatal error:
stdlib.h: No such file or directory
 #include_next <stdlib.h>
                         ^
compilation terminated.

The includes directories specified in the
CMakeFiles/main.dir/includes_CSS.rsp seems to be the culprit:

$ cat CMakeFiles/main.dir/includes_CXX.rsp
-isystem /usr/x86_64-w64-mingw32/include 

Removing that option from the file ends with a successful build. I
don't understand why it does not work with that because stdlib.h can be
found as /usr/x86_64-w64-mingw32/include/stdilb.h.

Do you have any clue?

Regards,

-- 
David Demelier