[CMake] "Pre-configure" step in CMake

[Matthäus G. Chajdas]

Hi,

that sounds like it would do the trick. I wasn't aware that
execute_process will block the script until it's done executing. Need to
check this out but that definitely looks like the way to go, thanks!

Cheers,
  Matthäus

Am 24.09.2015 um 10:14 schrieb Tamás Kenéz:
> What if you call your dependency-fetcher script with a straight
> macro/function call or `include` or `execute_process` instead of putting
> it into a custom target? I'm thinking of something like this:
> 
>     set(DEP_SCRIPT_OUT ${CMAKE_CURRENT_BINARY_DIR}/dep-script-out.cmake) 
>     if(NOT EXISTS "${DEP_SCRIPT_OUT}")
>       execute_process(${CMAKE_COMMAND}
>         -DC_COMPILER_ID=${CMAKE_C_COMPILER_ID}
>         -DC_COMPILER_VERSION=${CMAKE_C_COMPILER_VERSION}
>         -DDEP_SCRIPT_OUT =${DEP_SCRIPT_OUT}
>         -P dependency-fetcher.cmake)
>     endif()
>     include(${DEP_SCRIPT_OUT})
> 
> or, simply:
> 
>     if(NOT DEPENDENCIES_FETCHED)
>       include(dependency-fetcher.cmake)
>       # fetch_dependencies() # call it in case it's implemented as a
> macro/function
>       set(DEPENDENCIES_FETCHED ON CACHE BOOL "" FORCE)
>     endif()
> 
> In the latter case there's no need to write the variables into a script
> since the fetcher runs in the same scope.
> 
> Tamas
> 
> 
> On Wed, Sep 23, 2015 at 9:49 PM, Matthäus G. Chajdas <cmake at anteru.net
> <mailto:cmake at anteru.net>> wrote:
> 
>     Hi,
> 
>     I'm trying to solve the following the problem: I have a C++ application
>     and a dependency fetching script. I want to simplify the initial build
>     such that the following happens: On the first run of cmake, the compiler
>     ID and version is passed to an external script, which fetches some
>     pre-build binaries. It then writes a CMake file which contains basically
>     only set(FOO_INCLUDE_DIR /dep-dir), set(FOO_LIBRARY_DIR /dep-dir)
>     commands. CMake would then read this file and subsequent find_library
>     calls would pick up the values from this new CMake file. The idea is
>     that "actual" build is dependent on this first dependency step, but it's
>     already within the CMake framework so I can grab the compiler info and
>     other build info.
> 
>     The obvious problem is that while I can easily run the external script
>     by using configure_file, and have a custom target that does the
>     dependency fetching and CMake configure file generation. But I don't see
>     an easy way to get CMake to make the "rest of the project" depend on
>     that configure file. How can I make such a "two-stage" build with CMake?
> 
>     Cheers,
>       Matthäus
>     --
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