[CMake] Makefile doesn't automatically create executable path as Ninja

[Matthew Woehlke]

On 2013-09-03 13:21, Felipe Menezes Machado wrote:
> I'm having trouble understanding this behavior: what happens if the
> directory of the executable doesn't exist?
>
> I created a minimum example CMakeLists.txt (where foo.cpp is just a hello
> world):
>
> add_executable(test/test.bin foo.cpp)
>
> If the "test" directory doesn't exist, should the build system create it?

Well, ninja seems to think so :-).

> Does that depend on the build system?

Yes; ninja has a feature where it creates any non-existing directories 
that are used by any outputs. At least make does not have a similar 
feature. I don't know about other generators (e.g. xcode, msvc).

> I tested with make, it gives an error when executing "ld":
>
> /usr/bin/ld: cannot open output file test/test.bin: No such file or
> directory
>
> The command that generates the executable and gives the error is (from
> "make VERBOSE=1"):
>
> /usr/bin/c++       CMakeFiles/test/test.bin.dir/foo.cpp.o  -o test/test.bin
> -rdynamic
>
> On the other hand, when I tested it with Ninja, it created the directory
> and finished without errors.

Interesting question. I suppose CMake could be taught to generate make 
rules to emulate ninja's behavior.

Whether or not such a thing should be done is an interesting question. 
(Especially as it probably should be done for all generators, it at all.)

-- 
Matthew