[CMake] Mixing non-CMake ExternalProjects using Visual Studio

[Braden McDaniel]

On Apr 11, 2013, at 11:27 AM, Braden McDaniel <braden at endoframe.com> wrote:

> On Apr 1, 2013, at 3:10 PM, Micha Hergarden <micha.hergarden at gmail.com> wrote:
> 
>> On 01-04-13 20:02, Braden McDaniel wrote:
>>> When mixing a CMake Visual Studio build that has ExternalProjects (that is, via ExternalProject_Add) that use non-CMake makefile builds, how does one resolve the mismatch between the *_<config> variables (CMAKE_CXX_FLAGS_RELEASE, etc.)?
>>> 
>>> Specifically, how do I propagate the build flags in the *_<config> variables down to the ExternalProject?  I can't seem to find a way in CMake that will let me pick which variable to propagate (that is, CMAKE_CXX_FLAGS_DEBUG when I'm building the Debug configuration, CMAKE_CXX_FLAGS_RELEASE when building the Release configuration, etc.).
>>> 
>>> One option seems to be just to build the makefile-based ExternalProject four times--one for each configuration CMake generates in its project files.  But that, too, has a problem: what if the makefile-based ExternalProject has a dependency on another ExternalProject with a CMake build?
>>> 
>>> Are there any good solutions to these sorts of problems?
>>> 
>> 
>> In my project I've added wrappers for each stage:
>> 
>> PATCH_COMMAND "${CMAKE_CURRENT_BINARY_DIR}/patchwrapper"
>> CONFIGURE_COMMAND "${CMAKE_CURRENT_BINARY_DIR}/configurationwrapper"
>> BUILD_COMMAND "${CMAKE_CURRENT_BINARY_DIR}/buildwrapper"
>> INSTALL_COMMAND "${CMAKE_CURRENT_BINARY_DIR}/installwrapper"
>> 
>> These wrappers include a defaults file that I create from a defaults.in, using configure_file command. That way I can set flags and all kinds of build related variables. Although officially it's not recommended to use it in generic cmake based projects, it works quite well for me as I don't distribute my project. I just use the external projects to precompile some third party tooling.
> 
> 
> Thanks... I've made quite a bit of progress with this approach.
> 
> I'm attempting to use cmake -P for the wrapper script and I've been mostly successful; though I've hit a bit of a speedbump that I'll outline in another posting.


The problem was that I was setting CMAKE_ARGS in ExternalProject_Add in order to invoke my CMake script; but setting CMAKE_ARGS has the effect of calling CMake twice (once to configure, once to build).  The second call would result in an error.

Using BUILD_COMMAND to invoke CMake with my script has the desired effect.  (Well, almost.  stdout from the build process now goes into a log file instead of being visible in the IDE's build output window.  But it'll do.)

-- 
Braden McDaniel
braden at endoframe.com