code review 4527070: runtime: fix mmap error return on linux.

runtime: fix mmap error return on linux.

Fixes issue 1511 again.

[dchest, 2011-05-20 19:38:12]

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[dchest, 2011-05-20 19:41:01]

I have little idea of what I am doing, so please correct me if I'm wrong.
runtime·mmap returned 12 instead of -12, so I consulted darwin's sys.s, and
changed the one for linux accordingly. It works for me.

[dchest, 2011-05-25 11:21:49]

Ping?

[iant, 2011-05-26 23:21:14]

This change is not correct, at least not by itself.  The call to mmap in
runtime·SysAlloc expects that any value < 4096 is a positive errno value.  Also
the implementations in linux/{386,amd64,arm}/sys.s must match.

I think it would be simpler to correct runtime·SysMap to test for positive
ENOMEM: adding one test and fixing the existing test.

Another problem is that runtime·SysReserve in linux/mem.c is wrong, at least it
does not act as its caller runtime·mallocinit expects.  mallocinit expects
SysReserve to return nil on error, but the Linux implementation actually returns
a positive errno value.  Want to fix that while you're at it?

[dchest, 2011-05-27 00:10:50]

Thank you! Please take another look.

On 2011/05/26 23:21:14, iant wrote:
> This change is not correct, at least not by itself.  The call to mmap in
> runtime·SysAlloc expects that any value < 4096 is a positive errno value. 
Also
> the implementations in linux/{386,amd64,arm}/sys.s must match.
> 
> I think it would be simpler to correct runtime·SysMap to test for positive
> ENOMEM: adding one test and fixing the existing test.

Done.

> Another problem is that runtime·SysReserve in linux/mem.c is wrong, at least
it
> does not act as its caller runtime·mallocinit expects.  mallocinit expects
> SysReserve to return nil on error, but the Linux implementation actually
returns
> a positive errno value.  Want to fix that while you're at it?

Fixed.

[dchest, 2011-05-27 00:16:48]

Removed "amd64" from change title and description, as it fixes 386 too.

[iant, 2011-05-27 04:39:07]

LGTM

[iant, 2011-05-27 04:43:35]

*** Submitted as http://code.google.com/p/go/source/detail?r=8f4462cc4bdc ***

runtime: fix mmap error return on linux.

Fixes issue 1511 again.

R=golang-dev, iant
CC=golang-dev
http://codereview.appspot.com/4527070

Committer: Ian Lance Taylor <iant@golang.org>