file(WRITE ...) behaves differently on Linux compared to Windows regarding escaped whitespaces?

Code
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1

Hi,

I wanted to automate the version-string generation from a git tag via CMake and came up with an approach very similar to the following.

main.c:

#include <stdio.h>

int main()
{
    printf("Hello World!\n");
    return 0;
}

CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

project(TestingCmake LANGUAGES C)

add_executable(TestingCmake main.c)

set(FILE_NAME ${CMAKE_CURRENT_BINARY_DIR}/test_file.c)

add_custom_command(
    OUTPUT ${FILE_NAME}
    COMMAND ${CMAKE_COMMAND}
        -DSTRING_CONTENT="text with whitespace"
        -DFILE_PATH="${FILE_NAME}"
            -P ${CMAKE_CURRENT_SOURCE_DIR}/CreateVersion.cmake
)

add_custom_target(CreateClControllerVersionFile ALL
    COMMAND ${CMAKE_COMMAND}
        -DSTRING_CONTENT="text with whitespace"
        -DFILE_PATH="${FILE_NAME}"
            -P ${CMAKE_CURRENT_SOURCE_DIR}/CreateVersion.cmake
)

add_dependencies(TestingCmake CreateClControllerVersionFile)

CreateVersion.cmake:

file(WRITE ${FILE_PATH} "${STRING_CONTENT}")

Doing so I encountered [to me] seemingly strange behavior:
- under Windows [CMake 3.23.2] I got the expected result in the output file

text with whitespace

- under Linux [CMake 3.21.3] I encountered

text\ with\ whitespace

Is this expected behavior?

Is there a way for me to tell CMake to unescape the whitespaces during writing to file?

Should I approach my goal in a totally different way?

Thankful for any help

Johannes

2

You may want the VERBATIM argument here. Another problem (which may avoid the issue) is that inner quotes don’t work in CMake.

Try "-DSTRING_CONTENT=text with whitespace"; that may avoid the need for the VERBATIM. Also the same fix for FILE_PATH.

3

Hi Ben,

thanks for the fast reply.

Your proposed solution with the surrounding quotes seems to work. Thanks. Could you hint me to somewhere, in order to understand why?

In addition I ended up using VERBATIM as well, because I also had ( and ) as part of the string - which needed to be escaped for the command line.

Thanks

Johannes

4

My Quoting In CMake article discusses the broader topic. It may fill in a few blanks for you.

5

Other than the docs, quoting only works on whole “words”. It is not like bash (or other shells) where paired quotes can be jammed together to perform concatenation; in CMake the quotes become literal when they are not paired around words.