[CMake] Top level target depending on a file

[Alexander Broekhuis]

Hi,


> CMake takes great care regarding dependencies on files which are needed
> to build targets, i.e. usually, it's not necessary to specify any extra
> dependencies of a target on a file. In my exemplary project, the README
> file is actually not needed to build the library target, so CMake does
> not add an appropriate dependency. However, the README file is needed
> to generate the ZIP file, so the latter must be a separate target with
> dependencies on its own, whereas the approach to generate the ZIP file
> by a TARGET-style custom command for the library target is wrong, IMO;
> one can just trigger the ZIP file target in this way. In other words:
> You have two targets with different dependencies - don't mix them up.
>

In my case the output is the ZIP file. So the zip file is produced by the
top level target, and I don't want/need a separate target for it.
The generated zip file (bundle) is the deployable unit which contains a
library and additional information needed (at runtime) to use the library,
which is located in the manifest file. If the manifest file changes,
without a change to the library source, the zip file still needs to be
regenerated. As such the output of the target depends on the manifest file,
hence the need for a dependency to a file.


>
> PS: Please don't drop the ML.
>

I am used to mailing lists having the reply-to set, will try to keep it in
mind.


>
> > 2011/12/13 Michael Hertling <mhertling at online.de>
> >
> >> On 12/12/2011 11:40 AM, Alexander Broekhuis wrote:
> >>> Hi,
> >>>
> >>> Can anyone help me with this? I haven't found a proper solution myself
> >> yet..
> >>
> >> Does the following examplary project do what you intend?
> >>
> >> CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
> >> PROJECT(P C)
> >> SET(CMAKE_VERBOSE_MAKEFILE ON)
> >> # The library target:
> >> FILE(WRITE ${CMAKE_BINARY_DIR}/f.c "void f(void){}\n")
> >> ADD_LIBRARY(f SHARED f.c)
> >> # The README file:
> >> FILE(WRITE ${CMAKE_BINARY_DIR}/README "Very important information!\n")
> >> # The ZIP file command:
> >> ADD_CUSTOM_COMMAND(OUTPUT ${CMAKE_BINARY_DIR}/f.zip
> >>    COMMAND zip -j ${CMAKE_BINARY_DIR}/f.zip
> >>                   ${CMAKE_BINARY_DIR}/README
> >>                   $<TARGET_FILE:f>
> >>    DEPENDS ${CMAKE_BINARY_DIR}/README)
> >> # The ZIP file target:
> >> ADD_CUSTOM_TARGET(zip ALL DEPENDS ${CMAKE_BINARY_DIR}/f.zip)
> >> # Trigger ZIP file target after library target:
> >> ADD_CUSTOM_COMMAND(TARGET f POST_BUILD
> >>    COMMAND ${CMAKE_COMMAND} -E remove ${CMAKE_BINARY_DIR}/f.zip
> >>    COMMAND ${CMAKE_COMMAND} --build ${CMAKE_BINARY_DIR}
> >>                             --config $<CONFIGURATION>
> >>                             --target zip)
> >>
> >> The basic idea is the decomposition of the ZIP file's generation into a
> >> custom target, an OUTPUT-style custom command and a TARGET-style custom
> >> command, the latter in conjunction with CMake's --build switch.
> >>
> >> Regards,
> >>
> >> Michael
> >>
> >>> 2011/12/8 Alexander Broekhuis <a.broekhuis at gmail.com>
> >>>
> >>>> Hi all,
> >>>>
> >>>> In my project, some top level targets depend on simple text files.
> These
> >>>> targets produce a zip file as output, this is done using a custom
> >> command
> >>>> with a post-build to a library target.
> >>>> Part of the zip file are some simple text files, which are included
> >> using
> >>>> some custom CPack handling inside the custom command.
> >>>>
> >>>> How can I let the top level target depend on these text files as well?
> >> In
> >>>> other words, if a text files changes, the zip file has to be
> >> regenerated.
> >>>> These text files are not generated or copied etc. So a simple DEPENDS
> >> would
> >>>> suffice. I know add_custom_command(OUTPUT has support for this, but am
> >>>> wondering how to do this with add_custom_command(TARGET.
> >>>>
> >>>> TiA!
> >>>>
> >>>> --
> >>>> Met vriendelijke groet,
> >>>>
> >>>> Alexander Broekhuis
> --
>
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-- 
Met vriendelijke groet,

Alexander Broekhuis
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