[cmake-developers] Generating buildsystem metadata from CMake

[Alexander Neundorf]

On Monday, March 30, 2015 19:04:10 Anton Makeev wrote:
> > On 24 Mar 2015, at 00:54, Stephen Kelly <steveire at gmail.com> wrote:
> > 
> > Tobias Hunger wrote:
> >> How about include_directories, compile_definitions and compile_flags?
> >> 
> >> So something along the lines of:
> >> 
> >> "include_directories" : ["/foo", "/opt"]
> >> "compile_definitions" : ["DEF=\"Foo\"", "OTHER_DEF=1"]
> >> "compile_flags": [ "-c" ]
> > 
> > Quoting Anton:
> > 
> > Anton Makeev wrote:
> >> The other thing that seems troubling to me is that since file, target,
> >> language compiler options are split into different parts of metadata, the
> >> IDE need to know exactly how to assemble them back into the compiler’s
> >> command line (e.g. what flags go first file’s or language’s), duplicating
> >> CMake's logic that may be different from version to version and from
> >> compiler to compiler. The exact command line is needed to get the actual
> >> and precise defines, include search paths etc. from the compiler.
> > 
> > Maybe he can chime in with more. I don't really know why the entire
> > command
> > line is needed instead of separate "include_directories" and
> > "compile_definitions" arrays as you and I suggested. Perhaps because that
> > would not include -fPIC for example, which causes __PIC__ to be defined.
> > 
> > Another item of note is that CMake does not know the compile flags as a
> > sequential container of individual flags currently, but it knows them as a
> > string (that's also why it appears as a string in my generated json
> > currently).
> 
> The problem with the following format:
> ---
> "include_directories" : ["/foo", "/opt"]
> "compile_definitions" : ["DEF=\"Foo\"", "OTHER_DEF=1"]
> "compile_flags": [ "-c" ]
> —
> Is that it’s incomplete and cannot be used directly:
> * include directories list misses compiler-defined search paths
> * quote include directories are not distinguishable
> * compiler definition do not include compiler-defined(built-in) definitions
> etc.


Code for detecting the built-in include dirs and definitions is in 
CMakeExtraGeneratorDetermineCompilerMacrosAndIncludeDirs.cmake. This is used 
currently by CMakeFindCodeBlocks.cmake and CMakeFindEclipseCDT4.cmake, i.e. 
the respective extra-generators, and the information is generated into the 
eclipse/codeblocks project files.
This could be used here too.

I don't really understand your second point. Can you elaborate ?

Alex

P.S. Actually I still fail to understand why this generic json generator will 
be implemented differently then the other extra-generators. Those could also 
be changed to be variable-activated, instead of generator-activated, if this 
is preferred. Without checking the code, I don't think there is a technical 
reason not to do this.