[7ca0fdf] Disable munmap() if it causes VM map holes

[Mike Hommey]

On Mon, Apr 16, 2012 at 10:19:13PM +0200, Mike Hommey wrote:
> On Mon, Apr 16, 2012 at 12:07:58PM -0700, Jason Evans wrote:
> > On Apr 16, 2012, at 8:08 AM, Mike Hommey wrote:
> > > I noticed something "interesting" with the test for VM map holes: If
> > > I compile it manually, it fails:
> > > 
> > >  Hoped for 0x7f835133d000, got 0x7f8350b3d000
> > >  0x7f835173d000..0x7f835133d000..0x7f8350f3d000..0x7f835073d000..0x7f8350b3d000
> > > 
> > > Apparently, this happens when *not* linking libm to the testcase. It
> > > also does happen when linking libm and some other library (tried
> > > pthread and stdc++).
> > 
> > What OS is this on?  The test should fail on Linux, but not OS X or
> > FreeBSD.  Linux has a VM map management quirk (on at least x86) that
> > causes accumulation of VM map holes under normal operation.
> 
> Linux x64. Kernel 3.2.
> 
> So, you are saying that this error is the "expected" behaviour, except I
> actually don't get it under "normal" conditions (those of configure.ac)

Since the test actually fails to find what it's supposed to find, why
not just "hardcode" that linux gets no munmap and others do?

Mike