go/build: introduce $GOCOMPILER environment variable

cmd/go: introduce support for $GCCGO env var

This variable allows users to select the compiler when using the
gccgo toolchain.

[minux, 2014-07-12 22:35:07]

why is it named $GOCOMPILER but not $GCCGO?

[pcc, 2014-07-12 22:44:40]

On 2014/07/12 22:35:07, minux wrote:
> why is it named $GOCOMPILER but not $GCCGO?

Quite simply because there exist Go compilers other than gccgo which would work
here.

[minux, 2014-07-12 23:35:33]

On Sat, Jul 12, 2014 at 6:44 PM, <pcc@google.com> wrote:

> On 2014/07/12 22:35:07, minux wrote:
>
>> why is it named $GOCOMPILER but not $GCCGO?
>
> Quite simply because there exist Go compilers other than gccgo which
> would work here.
>
but the argument to -compiler is gccgo, so the environment variable should
be $GCCGO
instead of $GOCOMPILER.

or put it another way, why $GOCOMPILER doesn't take effect when using the
gc toolchain?

[pcc, 2014-07-13 03:39:14]

On 2014/07/12 23:35:33, minux wrote:
> On Sat, Jul 12, 2014 at 6:44 PM, <mailto:pcc@google.com> wrote:
> 
> > On 2014/07/12 22:35:07, minux wrote:
> >
> >> why is it named $GOCOMPILER but not $GCCGO?
> >
> > Quite simply because there exist Go compilers other than gccgo which
> > would work here.
> >
> but the argument to -compiler is gccgo, so the environment variable should
> be $GCCGO
> instead of $GOCOMPILER.

That doesn't follow.

> or put it another way, why $GOCOMPILER doesn't take effect when using the
> gc toolchain?

It might make sense to teach the gc toolchain about this variable, but that is
outside the scope of this CL.

Peter

[minux, 2014-07-13 06:46:39]

On Jul 12, 2014 11:39 PM, <pcc@google.com> wrote:
> On 2014/07/12 23:35:33, minux wrote:
>> > On 2014/07/12 22:35:07, minux wrote:
>> >> why is it named $GOCOMPILER but not $GCCGO?
>> > Quite simply because there exist Go compilers other than gccgo which
>> > would work here.
from the user's POV, setting GCCGO=someothergocompiler means this compiler
emulate enough of gccgo's behavior that it could be treated as gccgo. and
this is indeed the case here.

>> but the argument to -compiler is gccgo, so the environment variable
>> be $GCCGO
>> instead of $GOCOMPILER.
> That doesn't follow.
at least it's inconsistent naming. if you insist on using GOCOMPILER, then
the argument to -compiler should change to something other than gccgo, and
we're back to the original problem.

one can think of this CL as just replacing the hardcoded command "gccgo"
with an environment variable, and in this case, choosing $GCCGO makes
perfect sense, if not for the sake of less confusion and more consistency.

[pcc, 2014-07-14 09:03:20]

On 2014/07/13 06:46:39, minux wrote:
> On Jul 12, 2014 11:39 PM, <mailto:pcc@google.com> wrote:
> > On 2014/07/12 23:35:33, minux wrote:
> >> > On 2014/07/12 22:35:07, minux wrote:
> >> >> why is it named $GOCOMPILER but not $GCCGO?
> >> > Quite simply because there exist Go compilers other than gccgo which
> >> > would work here.
> from the user's POV, setting GCCGO=someothergocompiler means this compiler
> emulate enough of gccgo's behavior that it could be treated as gccgo. and
> this is indeed the case here.
> 
> >> but the argument to -compiler is gccgo, so the environment variable
> >> be $GCCGO
> >> instead of $GOCOMPILER.
> > That doesn't follow.
> at least it's inconsistent naming. if you insist on using GOCOMPILER, then
> the argument to -compiler should change to something other than gccgo, and
> we're back to the original problem.
> 
> one can think of this CL as just replacing the hardcoded command "gccgo"
> with an environment variable, and in this case, choosing $GCCGO makes
> perfect sense, if not for the sake of less confusion and more consistency.

Okay, I've renamed it.

[aram, 2014-07-14 11:26:53]

Please add a link in the description with the golang-dev thread(s?).

[rsc, 2014-07-14 13:50:12]

LGTM

This is nice and simple. Thank you. I understand that llgo is not gccgo, but at
the same time it is mimicking gccgo, so it's fine for now, especially until llgo
is a production compiler.

[rsc, 2014-07-14 13:51:17]

*** Submitted as https://code.google.com/p/go/source/detail?r=6866fbf95095 ***

cmd/go: introduce support for $GCCGO env var

This variable allows users to select the compiler when using the
gccgo toolchain.

LGTM=rsc
R=rsc, iant, minux, aram
CC=axwalk, golang-codereviews
https://codereview.appspot.com/106700044

Committer: Russ Cox <rsc@golang.org>

[gobot, 2014-07-14 13:51:59]

This CL appears to have broken the plan9-386-cnielsen builder.
See http://build.golang.org/log/9492f410dac22c779679357a8a021937e0915c1c