[CMake] Re: premake build system

[Alexander Neundorf]

On Monday 17 December 2007, you wrote:
> Alexander Neundorf wrote:
> > On Monday 17 December 2007, Gonzalo Garramuño wrote:
> >> Bill Hoffman wrote:
> >>> Gonzalo Garramuño wrote:
> >>>>     * good for cross-compilation.
> >>>
> >>> CVS CMake (and the coming 2.6 CMake) have extensive support for cross
> >>> compilation.
> >>>
> >>> http://www.cmake.org/Wiki/CMake_Cross_Compiling
> >>
> >> I'm still having a lot of problems with it.  Even cross-compiling on a
> >> 64-bit machine for 32-bit builds is, afaik, not really possible without
> >> major hacking of Platform/UnixPaths.
> >
> > Ok, what are you doing exactly, what are the problems ?
>
> First, trying simple 32-bit compiles on a 64-bit machine (Ubuntu OS).

I'm not sure this really counts as "cross compiling".
Two basic assumptions were
-the executables for the target cannot run (in general) on the build host
-the target environment is completely different from the build host 
environment, i.e. with its own set of libraries and headers located in a 
separate subtree (as it is the case for embedded linux, Win CE, eCos, sdcc, 
AD compilers, Cray compilers etc.)
This is not really the case here.

I think there is a bug report about chosing these variants you need correctly.

> For 32-bit compiles on a 64-bit machine, the problem is that UnixPaths
> does not change the location where it searches for files.
>
> First, CMAKE_SYSTEM_LIBRARY_PATH is set incorrectly to always search
> lib/ paths instead of lib32/ or lib64/ paths.  This will create warnings
> for the most part as the linker is usually smart.  However, if a library
> is not present on 32-bits, the 64-bits file will get picked up and the
> problem will only appear show up when linking, not during configuration.
>
> CMAKE_SYSTEM_PROGRAM_PATH also suffers from a similar issue.  This is an
> issue with modules that use pkgconfig, for example or that set settings
> from finding executables like ruby.  It isn't entirely clear to me if
> there is a standard location for 32-bit bin files (not libs) in Linux,
> thou.
>
> CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES is also wrong, adding both 64
> and 32 bits paths.
>
> Afaik, there's no variable indicating whether to compile for 32bits or
> not.  And cmake does not check for the -m32 flag at all.

CMAKE_SIZEOF_VOID_P
Maybe this should be honored more extensive ?

But this is an issue more for Brad (or Bill) ?

> I have my own UnixPaths and modules to work around most of the above,

Can you please post it ?

> but it would be good to have this working out of the box.

Yes.

> Recent versions of cmake seem to have also added this:
>
> # Enable use of lib64 search path variants by default.
> SET_PROPERTIES(GLOBAL PROPERTIES FIND_LIBRARY_USE_LIB64_PATHS TRUE)
>
> which seems highly undesirable or a so far undocumented feature.

Brad, Bill ?

> ---
> For cross-compiling, I was trying to do some compiles from my Unix box
> to windows using a unix-mingw32 to windows toolchain.  I was utterly
> unsuccessful.  I just kept fixing one error only to find another one.  I
> had followed the cmake wiki for cross-compiling, but there were still
> many issues with paths in modules and the like.  If you want to walk me
> thru it, I'll start a new thread with the errors I find as I go thru it
> again. 

Yes, please.
It should work and I'm happy about feedback.

Alex