[LLVMdev] [cfe-dev] [RFC] Raising LLVM minimum required MSVC version to 2013 for trunk

[Aaron Ballman]

On Mon, Feb 9, 2015 at 8:36 AM, Greg Bedwell <gregbedwell at gmail.com> wrote:
> We've just encountered an issue with ninja and VS2013 when using versions of
> CMake prior to 2.8.12.1.  This isn't a combination that we typically use so
> we've not run into it previously in our own builds.  It isn't specifically
> tied to upgrading the minimum version as it's a problem that already exists
> but I figure we'll hit it sooner or later on one of the bots as people start
> to use 2013 so best to deal with it sooner.  Essentially, when building any
> configuration through ninja with debug data enabled with anything more than
> -j1 we'll hit an error like:
>
> C:\work\public_svn\llvm\lib\Support\APInt.cpp : fatal error C1041: cannot
> open program database
> 'c:\work\public_svn\build-vs2013-native-ninja\lib\llvmsupport.pdb'; if
> multiple CL.EXE write to the same .PDB file, please use /FS
>
> Here's the relevant CMake tracker which shows the fix going into 2.8.12.1:
> http://www.cmake.org/Bug/view.php?id=14492
>
> I think our options are to either require CMake 2.8.12.1 for VS2013/ninja
> builds (but I don't know how feasible this is) or we can put our own
> workaround into our CMakelists to push the /FS switch when using Ninja and
> Visual Studio, unless someone has any better ideas?
>
> Any thoughts?  Is this a blocker for updating the minimum version?

I'm not certain I see it as a blocker since upgrading CMake should not
be too difficult (2.8.12.1 was released in Nov 2013). Whether we want
to require 2.8.12.1 is a different ball of wax, but for just the Ninja
+ MSVC build, I don't think that's too onerous (then again, I don't
use Ninja for my builds, either).

~Aaron