code review 703041: runtime: add Callers

runtime: add Callers

cut copies of traceback from 6 to 1.

[rsc, 2010-03-23 21:20:34]

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

I'd like you to review this change.

[r, 2010-03-23 21:29:01]

http://codereview.appspot.com/703041/diff/2001/3003
File src/pkg/runtime/amd64/traceback.c (right):

http://codereview.appspot.com/703041/diff/2001/3003#newcode35
src/pkg/runtime/amd64/traceback.c:35: for(iter = 0; iter < 10000 && n < m;
iter++) {	// iter avoids looping forever
10000 seems too large but it's ok if you want it

http://codereview.appspot.com/703041/diff/2001/3003#newcode48
src/pkg/runtime/amd64/traceback.c:48: // The 0x48 byte is only on amd64.
ouch

what happens on 386?  arm?

can you make this test  a pluggable callout?

[rsc, 2010-03-23 21:32:52]

> http://codereview.appspot.com/703041/diff/2001/3003
> File src/pkg/runtime/amd64/traceback.c (right):
>
> http://codereview.appspot.com/703041/diff/2001/3003#newcode35
> src/pkg/runtime/amd64/traceback.c:35: for(iter = 0; iter < 10000 && n <
> m; iter++) {    // iter avoids looping forever
> 10000 seems too large but it's ok if you want it

now 100.

> http://codereview.appspot.com/703041/diff/2001/3003#newcode48
> src/pkg/runtime/amd64/traceback.c:48: // The 0x48 byte is only on amd64.
> ouch
>
> what happens on 386?  arm?

386 works, because of the // skip 0x48 byte on amd64 line.

arm will be completely different because it has a link register.
(this code isn't used for arm.  arm didn't have a working
traceback before this CL, and still doesn't.  i did delete
the old, probably buggy, commented out copy of the amd64
code from the arm file.)

> can you make this test  a pluggable callout?

maybe but the surrounding traceback code is still
amd64/386 specific.  or at least "no link register"-specific,
which amounts to the same thing at the moment.

russ

[r2, 2010-03-23 21:34:14]

LGTM

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[rsc, 2010-03-24 00:01:20]

*** Submitted as http://code.google.com/p/go/source/detail?r=fc2507961bf0 ***

runtime: add Callers

cut copies of traceback from 6 to 1.

R=r
CC=golang-dev
http://codereview.appspot.com/703041