[Cmake] What I don't understand about CMake

[Stefano Barbato]

Bill, thanks for your reply.

I understand what you wrote but we all know that it's very difficult to force 
users to download and install something new and, even worse, something of 
which they probably don't even understand the usefullness and expecially if 
the build environment is much bigger then the package itself.

So knowing that many multi-platform apps/libraries used the multi-makefiles 
method of building on different machines (see vim, zlib and many others) I 
think would be great to use CMake to generate such makefiles. Having CMake 
would be better but generating makefiles should be an option I think.

Pre-generated makefiles would probably work without change on Windows 
paltforms where is more difficult to find substantial differences.  On more 
difficult platforms a small program able to set simple run-time variables 
(i.e. make variables)  based on the end-user machine could be enough to 
successfully 'make all' without running CMake.  Do we really need the whole 
CMake to find end-user paths? Couldn't a autogenerated C++ program find all 
interesting paths and set variables or modify a Makefile or create a sort of 
config.make with all paths to include in the other Makefiles?

My developer dream would be a system that let you create project files with 
few lines of text, as CMake does, and generates a set of files that included 
into the my software's distribution package would handle compiling 
automatically without any external requirement. Oh well, I mean without 
including the CMake sources into my tar.gz :)


stefano


On Wednesday 12 November 2003 16:27, William A. Hoffman wrote:
> CMake IS required to be installed by the end users.
>
> Here is the explaination. The only tool that is really shared across all
> platforms is the c/c++ compiler.  The build system can not depend on
> "common" tools because there are none.  A typical configure script depends
> on: sh, sed, echo, /dev/null, test, chmod, hostname, and cat.  In short, a
> fairly complete UNIX environment.  So, CMake depends on the one common
> tool, the c/c++ compiler.   It was felt that for a c/c++ project this would
> not be too much to ask. The union of available shell functions is very
> small across windows and UNIX.  CMake is in a sense a small portable shell.
>
> It really comes down two this.  With autoconf, windows users must install
> a UNIX compatibility layer like cygwin or mingw, and they can not use IDE
> build tools, but must use command line make.   With CMake, both windows and
> UNIX users have to install one program CMake, and after running cmake can
> use the system build tools.
>
> It really would not work very well to generate makefiles and move them
> to a different machine.   CMake finds all the paths for a particular
> machine. And if all machines were the same, we would not need cmake or
> autotools.
>
> One solution, might be to include some sub-set of cmake sources inside a
> project, and build it.   However, many projects depend on gnu make and do
> not include the source or build gnu make for each project.  They just
> expect users to download and install gnu make first.
>
>
> -Bill
>
> At 10:06 AM 11/12/2003, Stefano Barbato wrote:
> >I read CMake documentation and examples but there's something I don't
> >understand about CMake.
> >
> >I think that what's good about autotools is that the build environment can
> > be shipped with the source package because of its small size but CMake is
> > big to distribute with all packages.
> >
> >So I thought that CMake had to be installed on developers machines and
> > that with a single command it could generate *all* supported
> > platform-native makefiles or project files that would be included into
> > distribution packages. Probably a small auto-compiling program able to
> > choose between generated makefiles/prjfiles (based on on-site tests)
> > could be easily included into the distribution source archive (I used
> > this approch when coding my simple unit testing engine where the engine
> > core is distributed as source file and auto-compiled on end-user machine
> > before anything else).
> >
> >But my CMake installation seems to be able to generate only my platform
> >Makefiles.
> >
> >So must CMake be installed on destination end-user PCs for them to be able
> > to compile? can CMake generate all supported makefiles and project files
> > at once? Does this message make any sense? :)
> >
> >Thanks.
> >
> >Stefano Barbato
> >
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