code review 4082047: cgo: improve error reporting slightly.

cgo: improve error reporting slightly.
If there were warnings or errors in the user code,
cgo would print the first error from gcc and then stop,
which is not helpful.
This CL makes cgo ignore errors from user code
in the first pass - they will be shown later.
It also prints errors from user preamble code
with the correct line numbers.
(Also fixed misleading usage message).

[rog, 2011-01-28 12:22:35]

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

I'd like you to review this change.

[iant, 2011-01-29 06:43:19]

LGTM but wait for Russ.

[rsc, 2011-01-30 17:07:40]

Looks good except for taking away the part where
the error shows the gcc input.  At the least that should
be preserved under a -v (verbose) flag.  That's invaluable
for understanding strange behavior.  I can understand
if it isn't helpful for day-to-day usage.

Russ

[rog, 2011-01-30 17:29:54]

initially i added a verbose flag, but then i noticed
the -debug-gcc flag and thought that was probably
sufficient. perhaps the usage message should be
changed to mention it though.

On 30 January 2011 17:07, Russ Cox <rsc@golang.org> wrote:
> Looks good except for taking away the part where
> the error shows the gcc input.  At the least that should
> be preserved under a -v (verbose) flag.  That's invaluable
> for understanding strange behavior.  I can understand
> if it isn't helpful for day-to-day usage.
>
> Russ
>

[rsc, 2011-01-30 21:17:48]

LGTM

One minor fix (as you suggested).

http://codereview.appspot.com/4082047/diff/17001/src/cmd/cgo/main.go
File src/cmd/cgo/main.go (right):

http://codereview.appspot.com/4082047/diff/17001/src/cmd/cgo/main.go#newcode102
src/cmd/cgo/main.go:102: os.Exit(2)
flag.PrintDefaults()
os.Exit(2)

[rog, 2011-01-31 09:07:56]

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

Please take another look.

[rsc, 2011-01-31 19:31:37]

*** Submitted as fcf755cfceb6 ***

cgo: improve error reporting slightly.
If there were warnings or errors in the user code,
cgo would print the first error from gcc and then stop,
which is not helpful.
This CL makes cgo ignore errors from user code
in the first pass - they will be shown later.
It also prints errors from user preamble code
with the correct line numbers.
(Also fixed misleading usage message).

R=iant, rsc
CC=golang-dev
http://codereview.appspot.com/4082047

Committer: Russ Cox <rsc@golang.org>