code review 849041: godefs: fix handling of negative constants

godefs: fix handling of negative constants

[rsc, 2010-03-30 08:39:18]

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

I'd like you to review this change.

[r, 2010-03-30 17:04:37]

http://codereview.appspot.com/849041/diff/2001/3001
File src/cmd/godefs/main.c (right):

http://codereview.appspot.com/849041/diff/2001/3001#newcode303
src/cmd/godefs/main.c:303: Bprint(bout, lang->constfmt, con[i].name,
con[i].value & 0xFFFFFFFF);
i'm not sure this is a fix.  if you have a negative 32-bit constant on 32-bit
integers, how does this help?

[rsc, 2010-03-30 17:22:28]

> http://codereview.appspot.com/849041/diff/2001/3001#newcode303
> src/cmd/godefs/main.c:303: Bprint(bout, lang->constfmt, con[i].name,
> con[i].value & 0xFFFFFFFF);
> i'm not sure this is a fix.  if you have a negative 32-bit constant on
> 32-bit integers, how does this help?

value is an int64.
i believe that the way we use godefs, we only see
"negative" constants for c output on windows,
which is why the mask was originally added.
for the things we generate go output for, there
are plenty of slightly negative constants (-1, etc).

the original code at launch didn't have the mask at all.
the mask was added for windows but means that
regenerating the go files in syscall doesn't produce
the same code anymore.  this is an attempt to split
the difference and might need more tweaking later.

russ

[r, 2010-03-30 17:25:03]

LGTM

[rsc, 2010-03-30 17:42:17]

*** Submitted as http://code.google.com/p/go/source/detail?r=a177136393e5 ***

godefs: fix handling of negative constants

R=r
CC=golang-dev
http://codereview.appspot.com/849041