[CMake] adding a custom command with the file name as a target

[David Cole]

On Fri, Mar 11, 2011 at 12:05 PM, Jim Newsome <jnewsome at cmu.edu> wrote:
> Unfortunately it seems that the target needs to have a different name
> from its dependencies. When building I get:
> make[2]: Circular CMakeFiles/hello.bin <- hello.bin dependency dropped.
>
> Another workaround I thought of is to change the output filename to,
> e.g., _hello.bin and have a command in the target to move _hello.bin
> to hello.bin. Unfortunately this forces _hello.bin to be regenerated
> every time. I suppose I could work around _that_ by copying instead of
> moving, but that's getting fairly ugly.
>
> On Fri, Mar 11, 2011 at 11:56 AM, Tyler <tyler at cryptio.net> wrote:
>> The target in the Makefile is created with the add_custom_target()
>> call. So just change yours to:
>>
>> add_custom_target(hello.bin ALL DEPENDS hello.bin)
>>
>> hth,
>> tyler
>>
>> On Fri, Mar 11, 2011 at 7:58 AM, Jim Newsome <jnewsome at cmu.edu> wrote:
>>> I'd like to do something like add_custom_command, with the output file
>>> name as a target in the generated makefile. Is there an elegant way of
>>> doing this?
>>>
>>> The closest I've come is:
>>> add_executable (hello hello.c)
>>> add_custom_command(OUTPUT hello.bin
>>>                    COMMAND objcopy --output-format=binary hello hello.bin
>>>                   DEPENDS hello
>>>                   COMMENT "objcopying hello to hello.bin")
>>> add_custom_target(bin ALL DEPENDS hello.bin)
>>>
>>> However, the target name in the generated makefile is 'bin' rather
>>> than 'hello.bin'. Is there a way to make 'hello.bin' itself a target
>>> in the generated makefile?
>>
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How about making the *named output* of your custom command simply be a
sentinel file (with a different name) that just happens to produce the
real file (with the same name as the target)...?

Something like this:

add_executable (hello hello.c)
add_custom_command(OUTPUT hello.bin.sentinel
                  COMMAND objcopy --output-format=binary hello hello.bin
                  COMMAND ${CMAKE_COMMAND} -E touch hello.bin.sentinel
                  DEPENDS hello
                  COMMENT "objcopying hello to hello.bin")
add_custom_target(hello.bin ALL DEPENDS hello.bin.sentinel)

Does that work?