[LLVMdev] RFC: Timeline for deprecating the autoconf build system?

[Tom Stellard]

On Wed, Nov 05, 2014 at 05:14:02AM +0000, Steven Stewart-Gallus wrote:
> Hello, thank you for the thoughts.
> 
> > Have you seen the docs for CMake3.0 [1] (see cmake-buildsystem
> > especially)? They certainly aren't perfect but they are considerably
> > better than what was there before.
> 
> Okay, the documentation has come a long way since 3.0 although it
> still needs a bit of polish.
> 
> > I wouldn't say that much "important functionality is plain lacking",
> > it probably just isn't documented that well.
> 
> See the following.
> 
> > Installation prefix is set using the CMAKE_INSTALL_PREFIX cache
> > variable. You can set it at configure time,
> > 
> > $ cmake -DCMAKE_INSTALL_PREFIX=$HOME/root/usr/local  /path/to/llvm/src
> 
> Correct, but I cannot set it as a default in a configuration file so I
> need to specify it for every single package that I compile every time
> I configure it. I think this a very basic and obvious feature that
> CMake should support.
> 
> > I'm don't think it's necessary to set the rpath. If you read [2]
> > you'll see that you can just run the binaries in the build tree and
> > they have rpath set correctly (the installed binaries have rpath
> > removed)
> 
> I do in fact need to set the rpath so that I can link to a higher
> version of GCC's C++ standard library implementation installed there
> as LLVM does not build against an older version of GCC.
> 
> > As mentioned above you can override the installation directory
> > whenever you like (but it may trigger a rebuild).
> 
> > but it may trigger a rebuild
> 
> Yeah, that's not what I want.
> 
> > But you know you can
> > do this right?
> > 
> > $ make install DESTDIR=/some/path/
> 
> That's not the same behaviour at all!
> DESTDIR="$HOME/root/usr/local/stow/llvm" installs to
> "$HOME/root/usr/local/stow/llvm/$HOME/root/usr/local" instead of
> "$HOME/root/usr/local/stow/llvm" which is silly.
> 

Hi Steven,

Would you be able to file bugs at www.llvm.org/bugs for these missing
features CMake features and mark them as blocking 15732?  This way we
can track them more easily.

Thanks,
Tom

> > The documentation is probably the biggest problem. I actually quite
> > liked CMake (apart from its syntax and variable scoping rules) once
> > I understood the bits I needed to understand.  I probably have a
> > very different perspective from many though given that I used CMake
> > first and then tried autotools afterwards (I'll be honest... I don't
> > like it very much).
> 
> The fundamental difference between Autotools and CMake is that they
> are built for different users. CMake is built for the modern developer
> in 2014 on Linux, Windows, Mac OS X or FreeBSD. Autotools is primarily
> built for the Free Software enthusiast university student in 1980 who
> is compiling a package on his University's Unix like server (which
> could be any of many different ones). As such, Autotools is
> horrendously difficult for the developer to use but when used properly
> is extremely portable and easy to use for the university student who
> compiles the project.
> 
> Thank you,
> Steven Stewart-Gallus
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