[LLVMdev] Long-Term Support for LLVM Projects Extension to Build System?

[Hal Finkel]

----- Original Message -----
> From: "Eric Christopher" <echristo at gmail.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "John Criswell" <jtcriswel at gmail.com>, LLVMdev at cs.uiuc.edu, "Chris Bieneman" <beanz at apple.com>
> Sent: Thursday, June 18, 2015 7:57:40 PM
> Subject: Re: [LLVMdev] Long-Term Support for LLVM Projects Extension to Build System?
> 
> 
> On Thu, Jun 18, 2015 at 5:46 PM Hal Finkel < hfinkel at anl.gov > wrote:
> 
> 
> ----- Original Message -----
> > From: "Eric Christopher" < echristo at gmail.com >
> > To: "John Criswell" < jtcriswel at gmail.com >, LLVMdev at cs.uiuc.edu ,
> > "Chris Bieneman" < beanz at apple.com >
> > Sent: Thursday, June 18, 2015 7:14:06 PM
> > Subject: Re: [LLVMdev] Long-Term Support for LLVM Projects
> > Extension to Build System?
> > 
> > 
> > On Thu, Jun 18, 2015 at 5:07 PM John Criswell < jtcriswel at gmail.com
> > >
> > wrote:
> > 
> > 
> > On 6/18/15 6:49 PM, Eric Christopher wrote:
> > 
> > 
> > 
> > Hi John,
> > 
> > 
> > Long term we don't want to keep the burden of two build systems in
> > tree. CMake is turning out to be the build system we want because
> > of
> > its multi-platform support, etc and as soon as the CMake system can
> > do everything we can do with the autoconf/makefile build I plan on
> > turning down the support for that and removing the code.
> > 
> > Thanks, but I wasn't asking about autoconf vs. cmake.
> > 
> > 
> > 
> > 
> > Well, you are, but only sorta.
> > 
> > 
> > 
> > I'm wanting to know whether the ability to "plug into" the LLVM
> > build
> > system by external projects will be maintained. For example,
> > SAFECode doesn't have its own build system; it uses LLVM's, and it
> > does so without being a "patch" to the LLVM source tree. You can
> > put
> > the SAFECode source code anywhere you like, use LLVM-style
> > Makefiles
> > in its source code, and build it. All of the PROJ_SRC_ROOT,
> > PROJ_OBJ_ROOT magic in the autoconf build system is what permits
> > that feature to work.
> > 
> > Do you intend to keep this functionality when you replace autoconf
> > with cmake, or will all projects that want to use the LLVM build
> > system need to place their source code in the LLVM source tree? To
> > put it another way, do you intend to deprecate the
> > PROJ_SRC_ROOT/PROJ_OBJ_ROOT stuff?
> > 
> > While I've enjoyed the PROJ_* magic, I can see why you'd want to
> > get
> > rid of it. I just want to ensure that you are not planning on
> > replacing it.
> > 
> > 
> > Right. So this is a "autoconf/makefile build system vs cmake build
> > system" question as the Makefiles would, theoretically, all go away
> > at the end. I don't think anyone has plans of replacing this
> > functionality (Chris?), but migrating out of tree projects to hook
> > in via modifying the cmake build locally shouldn't be too bad.
> > 
> 
> This is also related to the metapoint that the cmake build system
> doesn't glob for source files (or anything else), unlike the
> makefile build system. This is understandable given the constraints,
> but we might want to restore some of that functionality for the
> purpose of supporting out-of-tree projects.
> 
> What I mean specifically, is that, for example, we could have a
> normally-empty directory tools/extensions, and tools/CMakeLists.txt
> could glob for directories in tools/extensions and call
> add_llvm_tool_subdirectory on all of them. It is true that you'd
> need to re-run cmake whenever you added something there (we could
> have a README in that directory to remind people of that), but that
> seems like a much smaller price than having to maintain a patched
> version of the upstream sources.
> 
> Sure, seems reasonable to me. I'm not working on the cmake transition
> so I'm just answering as far as "things I plan on deleting when I
> can delete" :)

Sounds good ;)

John, I think you're probably the best person to send a patch for this kind of thing since that way you can make sure the solution actually makes sense for you.

 -Hal

> 
> 
> -eric
> 
> 
> -Hal
> 
> > 
> > -eric
> > 
> > 
> > 
> > 
> > 
> > Regards,
> > 
> > John Criswell
> > 
> > 
> > 
> > 
> > 
> > 
> > Thanks!
> > 
> > 
> > -eric
> > 
> > 
> > 
> > On Thu, Jun 18, 2015 at 4:47 PM John Criswell < jtcriswel at gmail.com
> > >
> > wrote:
> > 
> > 
> > Dear All,
> > 
> > Will the LLVM project system (the extension to the build system
> > that
> > allows sub-projects to reuse the LLVM Makefiles) be maintained long
> > term, or is the slow push to CMake intending to deprecate this
> > functionality?
> > 
> > We used this feature a lot for research projects at UIUC, but if
> > the
> > current maintainers of the build system are planning on deprecating
> > it,
> > I'll have my students avoid using it.
> > 
> > Regards,
> > 
> > John Criswell
> > 
> > --
> > John Criswell
> > Assistant Professor
> > Department of Computer Science, University of Rochester
> > http://www.cs.rochester.edu/u/criswell
> > 
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> > 
> > 
> > --
> > John Criswell
> > Assistant Professor
> > Department of Computer Science, University of Rochester
> > http://www.cs.rochester.edu/u/criswell
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory