why can't wsl be called from cmake scripts? - cmake

Question

I have bash scripts that generate c++ files and I would like to call them from an add_custom_command() in cmake. On windows, I'd like to call the bash script through wsl (windows subsytem for linux). cmake configures fine (finding wsl.exe), but on build it complains that:
'C:\Windows\System32\wsl.exe' is not recognized as an internal or external command,
Here is a simple cmake script to recreate. It succeeds in a linux environment (including wsl), but fails in the native windows environment.
cmake_minimum_required(VERSION 3.7)
project(WhyNotWSL)
set(source ${CMAKE_SOURCE_DIR}/Input/main.cpp)
set(target generated.cpp )
if (WIN32)
find_program(WSL wsl)
message("WSL is ${WSL}")
set (command ${WSL} cp ${source} ${target})
else()
set (command cp ${source} ${target})
endif()
message("command is ${command}")
add_custom_target( ${target} )
add_custom_command(
OUTPUT ${target}
COMMAND ${command}
DEPENDS ${source}
COMMENT "Generated ${target}"
)
add_custom_target(p ALL
DEPENDS ${target}
)
add_executable(hello ${target})
The following output is from cmake configure:
-- Building for: Visual Studio 16 2019
-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.18363.
-- The C compiler identification is MSVC 19.27.29110.0
-- The CXX compiler identification is MSVC 19.27.29110.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.27.29110/
bin/Hostx64/x64/cl.exe - 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: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.27.2911
0/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
**WSL is C:/Windows/System32/wsl.exe**
**command is C:/Windows/System32/wsl.exe;cp;D:/Development/CMakeWSLTest/Input/main.cpp;generated.cpp**
-- Configuring done
-- Generating done
-- Build files have been written to: D:/Development/CMakeWSLTest/BUILD
And the following is the output from cmake build
Microsoft (R) Build Engine version 16.7.0+b89cb5fde for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.
Checking Build System
Building Custom Rule D:/Development/CMakeWSLTest/CMakeLists.txt
Building Custom Rule D:/Development/CMakeWSLTest/CMakeLists.txt
Generated generated.cpp
'C:\Windows\System32\wsl.exe' is not recognized as an internal or external command,
operable program or batch file.
For the record, the following works from a DOS shell:
>C:\Windows\System32\wsl.exe cp ../Input/main.cpp generated.cpp

Answer 1

Try giving HINTS to find_program() and point to C:\Windows\Sysnative
Something like this:
if (WIN32)
find_program(WSL wsl HINTS C:/Windows/Sysnative)
message("WSL is ${WSL}")
set (command ${WSL} cp ${source} ${target})
else()
set (command cp ${source} ${target})
endif()
Rationale here: https://superuser.com/a/1528297/2201 but basicly, this could be caused by your cmake buil. find_program() finds executable with absolute path that then should be different when it actually gets called during the build, it should actually point the binary from another location due to inherited build type of parent process of your build.
Maybe..