[cfe-dev] RFC: Upcoming Build System Changes

[Chris Lattner]

On Oct 27, 2011, at 11:28 PM, Óscar Fuentes wrote:

> Chris Lattner <clattner at apple.com> writes:
> 
>> There are several major problems with CMake IMO:
>> 
>> 1. It generates really slow build systems.
> 
> In my Linux box, last time I checked (long time ago) the cmake build was
> a bit faster than the Makefiles. But this is a tricky terrain, because
> they are not identical, not on the features supported (and some have an
> impact on build-time) nor even on the options passed to the compiler.

The makefiles are known to be really slow, among other problems being based on recursive make.  One goal of this is to get a non-recursive makefile generated.  We've prototyped this in the past and found it to be substantially faster than the recursive makefile.

>> 2. The build system generated by cmake is absolute garbage, at least
>> for Xcode.  The build times of it are really bad, and having to work
>> with it in the IDE is even more terrible.
> 
> AFAIK there is a Xcode project file on the LLVM source tree.

Nope, there was once but it was removed a long time ago though.

> Are the
> LLVM makefiles used by the Xcode project?

No, it is generated by Cmake.

> If the Xcode project files
> generated by cmake is not satisfactory, can't they use the Makefiles
> generated by cmake instead?

Xcode can drive a makefile, but it doesn't provide any of the IDE integration features, e.g. clang code completion.

-Chris