[cfe-dev] Building Clang on Windows

[Hussien Hussien via cfe-dev]

The problem is that by default VS2017 builds Clang in parallel to how many
cores you have. When I build LLVM/Clang, I've noticed the default setting
will almost instantly consume 100% of my RAM and I have 16GB of RAM and
32cores.

To turn off parallel building, mark the appropriate CMAKE variables:

LLVM_PARALLEL_COMPILE_JOBS:STRING
Define the maximum number of concurrent compilation jobs.
LLVM_PARALLEL_LINK_JOBS:STRING
Define the maximum number of concurrent link jobs.

Also in Visual Studio, in Tools > Projects and Solutions > Build and Run,
set
'maximum number of parallel project builds to 1.

Hussien H.

On Sun, Oct 7, 2018 at 9:22 AM degski via cfe-dev <cfe-dev at lists.llvm.org>
wrote:

> Sorry to barge in.
>
> >> I remember doing so at one point when I was still using Windows, and
> found
> >> my system much more responsive overall. But that was ~10 years ago and I
> >> guess it's not a common setup.
>
> 10 years ago does not seem very relevant, both Windows and VS are very
> different now. Also "... found my system much more responsive overall ..."
> very much sounds like placebo/snake-oil.
>
> >> If msbuild is 32-bit, why would that cause the (64-bit?) cl.exe process
> to
> >> run out of memory?
>
> I doubt msbuild is allocating much memory at all, but is the 64-bit
> version of cl.exe being called from msbuild? You need to up the build
> output so you can see what compiler is being called. Sounds like ninja is
> calling the 64-bit version, while msbuild is (could be, I'm speculating)
> using the 32-bit version to cross-build [and runs out of addressable
> space]. The VS defaults are all 32-bit.
>
> degski
> --
> *“If something cannot go on forever, it will stop" - Herbert Stein*
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