[CMake] add_custom_command/get_target_property bug on Windows?

[Steven Wilson]

Thanks!  These comments have the insight that I needed!

Steve

On Thu, Oct 22, 2009 at 6:22 AM, Brad King <brad.king at kitware.com> wrote:

> Steven Wilson wrote:
>
>> Consider the following simple C++ file foo.cpp:
>>
>> #include <iostream>
>>
>> int main()
>> {
>>    std::cout << "bar" << std::endl;
>>    return 0;
>> }
>>
>>
>> Now consider the following CMakeLists.txt file for foo.cpp:
>>
>>
>> cmake_minimum_required(VERSION 2.6)
>>
>> project(Bug)
>>
>> set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
>>
>>
>> add_executable(foo foo.cpp)
>>
>> get_target_property(FOO_LOCATION foo LOCATION)
>>
>> message("${FOO_LOCATION}")
>>
>> add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/bar
>>    COMMAND ${CMAKE_COMMAND} -E make_directory bat
>>    COMMAND chdir bat
>>    COMMAND ${FOO_LOCATION} > ${CMAKE_CURRENT_BINARY_DIR}/bar
>>    DEPENDS foo
>> )
>>
>>
>> add_custom_target(Bar DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/bar)
>>
>>
>> When you configure this project using the Windows Visual Studio 9
>> generator, the generation step correctly displays(ie from the message()
>> command) the value C:\path\to\build\directory\bin\$(OutDir)\foo.exe for the
>> variable FOO_LOCATION.
>> The problem comes in the add_custom_command step.   The generator writes
>> the following line into the .vcproj file:
>>
>> bin\$(OutDir)\foo.exe > C:\path\to\build\directory\bar
>>
>> What I'm pointing out is that the generator puts a path to foo.exe that is
>> not the full path name and this behavior causes the add_custom_command build
>> step to fail because the custom command includes a chdir command so the
>> current working directory has changed and bin\$(OutDir)\foo.exe is not
>> longer available.
>>
>> Now, if you instead modify the add_custom_command the line to read:
>>
>> COMMAND "..\${FOO_LOCATION}|" > ${CMAKE_CURRENT_BINARY_DIR}/bar
>>
>> the generator instead puts the following in the project files:
>>
>> ..\C:\path\to\build\directory\bin\$(OutDir)\foo.exe
>>
>> ?!?
>>
>> The correct path now appears, but it is wrong because of the ..\ prepended
>> to the value.
>>
>> What is going on?   Why doesn't the value of FOO_LOCATION always and
>> everywhere stay C:\path\to\build\directory\bin\$(OutDir)\foo.exe?
>>
>
> It's converted to a path relative to the expected working directory
> of the custom command.  This is the current binary directory by
> default, or can be set with the add_custom_command() call through the
> WORKING_DIRECTORY option.  You can use file(MAKE_DIRECTORY) to prepare
> the directory at CMake time, or a separate custom command to make it.
>
> FYI, the LOCATION property is not necessary in CMake 2.6.  You can
> just name the target:
>
>  file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bat)
>  add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/bar
>    COMMAND foo > ${CMAKE_CURRENT_BINARY_DIR}/bar
>    DEPENDS foo
>    WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bat
>    )
>
> -Brad
>
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