r278882 - If possible, set the stack rlimit to at least 8MiB on cc1 startup, and work

[Joerg Sonnenberger via cfe-commits]

On Thu, Aug 18, 2016 at 11:33:49AM -0700, Richard Smith wrote:
> On Wed, Aug 17, 2016 at 6:35 AM, Joerg Sonnenberger via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
> 
> > On Wed, Aug 17, 2016 at 01:05:08AM -0000, Richard Smith via cfe-commits
> > wrote:
> > > Author: rsmith
> > > Date: Tue Aug 16 20:05:07 2016
> > > New Revision: 278882
> > >
> > > URL: http://llvm.org/viewvc/llvm-project?rev=278882&view=rev
> > > Log:
> > > If possible, set the stack rlimit to at least 8MiB on cc1 startup, and
> > work
> > > around a Linux kernel bug where the actual amount of available stack may
> > be a
> > > *lot* lower than the rlimit.
> >
> > Can you please restrict this to Linux? I'm quite opposed to overriding
> > system default limits, they exist for a reason.
> 
> 
> No, that wouldn't make any sense. It's not up to the operating system how
> an application decides to allocate memory (on the heap versus on the
> stack), and Clang's stack usage isn't going to be significantly lower on
> other kernels. If some BSD kernel's VM is unable to cope with this, we
> could spawn a thread with a suitable amount of stack space instead.

This is not about kernel bugs. It is about POLA -- programs are not
supposed to alter process limits. If GCC does it, it is a GCC bug.
That's no reason to introduce the same bug here. Using excessive stack
space due to deep recursion might be a QoI issue, but it is
fundamentally no different from any other out of memory condition. Those
kill clang just as easily.

Joerg