[CMake] Add dependencies to the automoc/autorcc target?

[Yves Frederix]

Hi Jacob,

Thanks for your answer. I am aware that add_custom_command() does not
create a target, hence the call to add_custom_target(generate_files),
followed by add_custom_command(TARGET generate_files...).

The presence of the sleep command is for illustration purposes only.
It delays the generation of 'myfile.txt' so that I can illustrate the
problem (in a parallel build the autorcc will be started before the
file is generated and the error will be shown).

Regards,
Yves

On Tue, Jan 17, 2017 at 12:47 PM, Jakob van Bethlehem
<jsvanbethlehem at gmail.com> wrote:
> Hej Yves,
>
> The problem is that the 'add_custom_command' does *NOT* create a new target,
> which seems to be what you assume, see
> https://cmake.org/cmake/help/v3.0/command/add_custom_command.html
>
> The signature you're using is supposed to be used to *add* a custom command
> to an *existing* target. In other words, it should read:
>
> add_custom_command(TARGET foo PRE_BUILD COMMAND ${CMAKE_COMMAND} -E touch
>   ${CMAKE_BINARY_DIR}/myfile.txt)
>
> (and hopefully it is immediately obvious that the 'sleep' command should go
> - CMake will never execute that command)
>
> Sincerely,
> Jakob
>
> On Tue, Jan 17, 2017 at 12:02 PM, Yves Frederix
> <yves.frederix+cmake at gmail.com> wrote:
>>
>> Hi all,
>>
>> I have a situation in which I would need to define a dependency for
>> the automoc target. Is it possible to do this somehow?
>>
>> Basically, I have a setup in which a resource that is to be embedded
>> is generated by another target. However, due to parallelism in the
>> build and the lack of a dependency of the _automoc target on this
>> target, I often get an error like :
>>
>>    RCC: Error in '.../build/resources.qrc': Cannot find file
>> '../build/myfile.txt'
>>
>> I tried adding a dependency using add_dependencies, but this doesn't
>> seem to work.
>>
>> Minimal example code is below (you will need to create an empty
>> main.cpp though). I am using CMake 3.7.1 with a VS generator. My build
>> command looks like 'cmake --build . -- -m'.
>>
>>
>> cmake_minimum_required(VERSION 3.7)
>>
>> project(test CXX)
>>
>> find_package(Qt5Quick REQUIRED)
>>
>> set(CMAKE_AUTORCC ON)
>>
>> # Define target that generates some files.
>> add_custom_target(generate_files)
>> add_custom_command(TARGET generate_files COMMAND sleep 1) # Wait a bit...
>> add_custom_command(TARGET generate_files COMMAND ${CMAKE_COMMAND} -E touch
>>   ${CMAKE_BINARY_DIR}/myfile.txt)
>>
>> # Write the .qrc file for embedding these generated files.
>> file(WRITE ${CMAKE_BINARY_DIR}/resources.qrc
>>   "<!DOCTYPE RCC><RCC
>>
>> version=\"1.0\">\n<qresource>\n<file>${CMAKE_BINARY_DIR}/myfile.txt</file>\n</qresource>\n</RCC>")
>>
>> add_library(foo SHARED main.cpp ${CMAKE_BINARY_DIR}/resources.qrc)
>> add_dependencies(foo generate_files)
>> target_link_libraries(foo PRIVATE Qt5::Quick)
>>
>>
>> Thanks!
>>
>> Regards,
>> Yves
>> --
>>
>> Powered by www.kitware.com
>>
>> Please keep messages on-topic and check the CMake FAQ at:
>> http://www.cmake.org/Wiki/CMake_FAQ
>>
>> Kitware offers various services to support the CMake community. For more
>> information on each offering, please visit:
>>
>> CMake Support: http://cmake.org/cmake/help/support.html
>> CMake Consulting: http://cmake.org/cmake/help/consulting.html
>> CMake Training Courses: http://cmake.org/cmake/help/training.html
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Follow this link to subscribe/unsubscribe:
>> http://public.kitware.com/mailman/listinfo/cmake
>
>