code review 7962045: cmd/nm: don't add filename elements for m symbols

cmd/nm: don't add filename elements for m symbols

The compilers used to generate only one 'm' symbol
to record the stack frame size for each function.

In cmd/nm, the 'm' and 'f' symbols are handled in
the same switch case with a special exception for
the symbol described above called ".frame".

Now that the compilers emit additional 'm' symbols
for precise garbage collection of the stack, the
current logic is incorrect. cmd/nm will attempt to
interpret these new 'm' symbols as 'f' symbols and
add them to the file name index table.

This fails with an out-of-memory condition when
zenter encounters an 'm' symbol with a very large
value (usually the .args symbol indicating a
variadic NOSPLIT function).

[ality, 2013-03-24 04:00:34]

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

I'd like you to review this change to
https://code.google.com/p/go/

[dave_cheney.net, 2013-04-01 12:43:10]

Hello,

This change looks pretty low impact. Could you please give a little bit of
background on what it fixes or what this patch will do.

Cheers

Dave

[ality, 2013-04-03 00:47:25]

Hello rsc@golang.org, dave@cheney.net (cc: golang-dev@googlegroups.com),

Please take another look.

[ality, 2013-04-03 00:49:22]

dave@cheney.net once said:
> This change looks pretty low impact. Could you please give a little bit
> of background on what it fixes or what this patch will do.

Sure. I updated the description. PTAL.

Thanks,
  Anthony

[gobot, 2013-04-03 08:30:01]

R=iant (assigned by dfc)

[iant, 2013-04-03 13:17:30]

LGTM

Thanks.

[ality, 2013-04-03 21:07:32]

iant@golang.org once said:
> LGTM
> 
> Thanks.

Can I submit this before Go 1.1?
Currently, 'go tool nm -a ...' just doesn't work.

  Anthony

[dave_cheney.net, 2013-04-03 21:31:55]

I believe this issue had met the cutoff. It would have been good to have an
issue to track it against, but don't worry about that now. 



On 04/04/2013, at 8:07 AM, Anthony Martin <ality@pbrane.org> wrote:

> iant@golang.org once said:
>> LGTM
>> 
>> Thanks.
> 
> Can I submit this before Go 1.1?
> Currently, 'go tool nm -a ...' just doesn't work.
> 
>  Anthony

[iant, 2013-04-04 00:32:54]

On Wed, Apr 3, 2013 at 2:07 PM, Anthony Martin <ality@pbrane.org> wrote:
> iant@golang.org once said:
>> LGTM
>>
>> Thanks.
>
> Can I submit this before Go 1.1?

Yes.

Thanks.

Ian

[ality, 2013-04-04 01:23:52]

*** Submitted as https://code.google.com/p/go/source/detail?r=267bb9854177 ***

cmd/nm: don't add filename elements for m symbols

The compilers used to generate only one 'm' symbol
to record the stack frame size for each function.

In cmd/nm, the 'm' and 'f' symbols are handled in
the same switch case with a special exception for
the symbol described above called ".frame".

Now that the compilers emit additional 'm' symbols
for precise garbage collection of the stack, the
current logic is incorrect. cmd/nm will attempt to
interpret these new 'm' symbols as 'f' symbols and
add them to the file name index table.

This fails with an out-of-memory condition when
zenter encounters an 'm' symbol with a very large
value (usually the .args symbol indicating a
variadic NOSPLIT function).

R=iant
CC=dave, gobot, golang-dev, rsc
https://codereview.appspot.com/7962045