code review 13394045: cmd/go: if there are C++ sources, use g++ as default ex...

cmd/go: if there are C++ sources, use g++ as default external linker

This will bring in the C++ standard library without requiring
any special #cgo LDFLAGS options.

When using gccgo, just add -lstdc++ to link line; this should
do no harm if it is not needed.

No tests, since we don't want to assume a C++ compiler.

Update issue 5629

[iant, 2013-09-04 15:16:20]

Hello golang-dev@googlegroups.com,

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

[iant, 2013-09-06 22:50:43]

Ping.

Basic idea is pretty simple.  Note that patch has changed since initial e-mail
to include gccgo support.

[minux1, 2013-09-09 19:12:47]

https://codereview.appspot.com/13394045/diff/7001/src/cmd/go/build.go
File src/cmd/go/build.go (right):

https://codereview.appspot.com/13394045/diff/7001/src/cmd/go/build.go#newcode...
src/cmd/go/build.go:1575: // specified the -extld or -extldflags option, then
if only -extldflags is given, i think the user's intention would be to
use whatever linker it should use when -extldflags is not there, and
then add those extra flags.

[iant, 2013-09-09 19:40:22]

https://codereview.appspot.com/13394045/diff/7001/src/cmd/go/build.go
File src/cmd/go/build.go (right):

https://codereview.appspot.com/13394045/diff/7001/src/cmd/go/build.go#newcode...
src/cmd/go/build.go:1575: // specified the -extld or -extldflags option, then
On 2013/09/09 19:12:47, minux wrote:
> if only -extldflags is given, i think the user's intention would be to
> use whatever linker it should use when -extldflags is not there, and
> then add those extra flags.

Makes sense.  Done.

[rsc, 2013-09-09 19:45:44]

LGTM

[iant, 2013-09-09 19:50:54]

*** Submitted as https://code.google.com/p/go/source/detail?r=ca80c16cf523 ***

cmd/go: if there are C++ sources, use g++ as default external linker

This will bring in the C++ standard library without requiring
any special #cgo LDFLAGS options.

When using gccgo, just add -lstdc++ to link line; this should
do no harm if it is not needed.

No tests, since we don't want to assume a C++ compiler.

Update issue 5629

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/13394045