Hej David,
You're either very confusing in explaining your needs or you just don't
understand what CMake does. CMake knows that it needs to build MY_LIB
before MY_APP, because supposedly you have written code in the
lists-file that tells CMake so.
I can't be sure, but I feel you really need to check out the
documentation a bit more; on the other hand, if you never created a
build-system before I think the available documentation is quite
overwhelming and maybe close to incomprehensible. It certainly took me
quite a while to figure out how to convert my manually coded Makefiles
into CMake lists-files properly.
Anyways: let me spit it out a bit for you. Suppose this is the structure
of your sources:
main_tree/
source1.cc
source2.cc
my_app.cc
my_lib/
src1.cc
src2.cc
(Note that I made the my_lib directory a sub-directory; this is not
strictly necessary, but certainly preferable)
Now we create a lists-file in the sub-dir. I'll not write all the
details, but provide the main parts you'll need:
add_library(MY_LIB src1.cc src2.cc)
Hej.... that's all there is to it. Of course you could and (probably)
should create a variable that stores the sources for MY_LIB. Now CMake
knows about the library and what sources to use for it. Let's move to
the main dir. Here we do:
add_subdirectory(my_lib)
add_executable(MY_APP my_app.cc)
target_link_libraries(MY_APP MY_LIB)
That's all there is to it. Now CMake knows that there is some executable
MY_APP that is to be compiled from my_app.cc (of course the list of
sources is not limited to one) and also that it needs MY_LIB to link it.
CMake will automatically make sure the library gets build before linking
- it must, since the executable can't be build without the library to
begin with. Your job is to write a lists-file that describes
dependencies - CMake will then figure out how the project is to be build
and creates Makefiles for it (BTW: reading your mail I got the feeling
that maybe you are under the impression that CMake actually builds the
project - if that's case, you misunderstood. CMake will create Makefiles
for you; subsequently you'll have to call make to build the project -
make help will get you a listing of all targets CMake created for you.
Or in yet other words: the two lines of code you wrote will never, ever,
build anything. It will only create Makefiles.)
Since you are new to CMake I'd also urge you to have a look at
http://www.cmake.org/cmake/help/cmake_tutorial.html
Hope this helps.
Greetsz, Jakob
On 06/17/2011 11:06 AM, David Springate wrote:
Hi,
Thanks for the reply - but I think you might have misunderstood my
question.
I want to setup CMake so that when I call Cmake like so (for MY_APP):
mkdir build && cd build
cmake .. -G Xcode
that the cmake call will be able to 'know' that it needs MY_LIB, find
where the MY_LIB CMakeLists.txt file is, build it, and then continue
with the cmake call for MY_APP.
Any ideas?
David
On 17 June 2011 08:18, J.S. van Bethlehem
<j.s.van.bethle...@astro.rug.nl
<mailto:j.s.van.bethle...@astro.rug.nl>> wrote:
Hej David,
>From your description I think all your build script needs to do is:
mkdir build && cd build
cmake ..
make MY_APP
Further, assuming your library also gets build with CMake, you
probably have an add_directory(../MY_LIB ../MY_LIB) in your main
lists-file (otherwise you should) and then the link_directories()
command is not needed. I created sort of a 'standard' machinery
for building a list of 'sub-packages' using CMake. It's not well
documented and probably still has many issues, but I could mail it
to you if you think it may help you get started and if you're
interested.
Greetsz,
Jakob
On 06/16/2011 11:54 PM, David Springate wrote:
Hi,
I am new to CMake - and whilst I am immediately impressed with
it's relative ease of use - I have a 'noob' question, I'm sure!
I have the following:
A library called MY_LIB that builds with a cmake command (I
have created a nice CMakeLists.txt file)
An application called MY_APP that builds a nice application -
and even links in MY_LIB using:
link_directories("../MY_LIB")
target_link_libraries(MY_APP MY_LIB)
Now, first of all I know that I'm not supposed to use relative
paths.. but we'll call a side issue.. (though I'd be happy to
hear the correct way of doing things!) - the real problem that
I have is this:
Give than MY_LIB is built using CMake and MY_APP is built
using CMake.. how can I setup my build scripts so that I can
call CMake once for MY_APP, it'll realise that it needs
MY_LIB, which hasn't yet been built, invoke CMake for MY_LIB
and then link itself with MY_APP?
I ask because I use libraries heavily to organise my code (and
reuse) and would love to switch to CMake for all my building
(XCode 4 has forced my hand!) but I can't seem to figure this out.
Please help a newcomer out - any help is greatly appreciated!
Thanks,
David
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