[Cmake] What I don't understand about CMake

[William A. Hoffman]

We have given this a lot of thought.   I think you could come up with
a solution that worked some of the time for some projects.  But for a general
solution it is not really possible.  Generating makefiles and distributing them
will only work for small projects that do not depend on much.  

The problem is that autoconf really depends on a big list of executables that
happen to be on most unix systems, but not on windows.   So, you have to get 
that functionality from somewhere. The plan is to have cmake be as available 
as say gnu-make is.  However, it really is a chicken and the egg problem.

I also do not agree with the argument that Windows does not need configuring.
Again, small projects may not, but then those projects maybe should just
have hard coded makefiles anyway.  As soon as you try and find/use external
software it is always installed in random places.

One idea we have thought about, is to create a minimum-cmake that can be 
incorporated into a project.  It would be built during the configure step
and then run on the project.   


-Bill


At 11:53 AM 11/12/2003, Stefano Barbato wrote:
>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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