[CMake] Unit tests, but not CTest

[Magnus Therning]

On 14/05/10 22:28, Michael Hertling wrote:
> On 05/14/2010 08:24 AM, Magnus Therning wrote:
[...]
>> Thanks for this analysis, it makes the problem a lot clearer to me.  One
>> thing it doesn't clarify is how ADD_CUSTOM_COMMAND( TARGET ... POST_BUILD )
>> could *ever* be useful. [...]
> 
> ADD_CUSTOM_COMMAND(TARGET ...) enhances the commands associated with the
> named target, i.e. you can hook into that target's build process:
> 
> CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
> 
> PROJECT(CUSTOM_COMMAND_DEMO C)
> 
> FILE(WRITE main.c "void main(){}")
> ADD_EXECUTABLE(exe main.c)
> 
> ADD_CUSTOM_COMMAND(TARGET exe PRE_BUILD COMMAND echo "Pre build")
> ADD_CUSTOM_COMMAND(TARGET exe POST_BUILD COMMAND echo "Post build")
> 
> After cmaking, look at the end of CMakeFiles/exe.dir/build.make:
> 
> [...]
> exe: CMakeFiles/exe.dir/main.c.o
> exe: CMakeFiles/exe.dir/build.make
> exe: CMakeFiles/exe.dir/link.txt
>         @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --red
> --bold "Linking C executable exe"
>         echo Pre\ build
>         $(CMAKE_COMMAND) -E cmake_link_script
> CMakeFiles/exe.dir/link.txt --verbose=$(VERBOSE)
>         echo Post\ build
> [...]
> 
> Thus, ADD_CUSTOM_COMMAND(TARGET ...) doesn't modify the dependencies of the
> named target but the associated commands. So, it provides a general
> possibility to have arbitrary commands run when a target is (re)built.

Ah, sorry, I managed to use the wrong word, "useful" when I really should have
written "used".  I can see its usefulness, indeed I *wanted* to use it myself.
However, earlier in this thread it became apparent that
add_custom_command( OUTPUT foo ... ) can't be used together with
add_custom_command( TARGET foo POST_BUILD ... ); the latter would *never* be
executed.  It was also apparent that add_custom_target( foo ... ) can't be
used with add_custom_command( TARGET foo POST_BUILD ...); the latter would
then *always* be executed.

Now you say that if I use add_executable( foo ... ) then I can use
add_custom_command( TARGET foo POST_BUILD ... ).  So, what does
add_executable( ... ) do?

I was under the impression that add_executable( ... ) deep down wasn't much
more than a wrapper around add_custom_command( OUTPUT ... ) (since that is the
only way I know to get anything built through the CMake scripts).  However now
you've made me think that add_executable( ... ) is a bit magical.  If that's
the case, then how does one go about adding full support for a language (i.e.
so that add_executable( ... ) can be used for that language) using nothing but
CMake scripts?

>> [...] I'm still to see an example of any buildable target that
>> such a post-build command can be connected to and only triggered on (re)build.
> 
> Imagine your add_ocaml_executable() using ADD_EXECUTABLE() instead of
> ADD_CUSTOM_COMMAND(OUTPUT ...); in this case, you would have a, say,
> fully-fledged CMake target which additional commands can be attached to by
> ADD_CUSTOM_COMMAND(TARGET ...), and indeed, that is a suitable place for
> your automated unit testing. Obviously, CMake's file-level targets defined
> by ADD_CUSTOM_COMMAND(OUTPUT ...) are not sufficient for this purpose
> although they appear as usual Make targets if others depend on them, but so,
> you've to specify the desired commands right in the
> ADD_CUSTOM_COMMAND(OUTPUT ...). Perhaps, this would be worth a feature
> request.

This seems to support my line of reasoning above, i.e. that adding full
language support for new language (i.e. making it possible to use
add_executable( ... ) on OCaml sources) isn't possible using CMake scripts
alone.  Is that correct?

/M

-- 
Magnus Therning                        (OpenPGP: 0xAB4DFBA4)
magnus＠therning．org          Jabber: magnus＠therning．org
http://therning.org/magnus         identi.ca|twitter: magthe

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