cmd/cgo: support for gccgo

[rsc]

Cgo-based packages that work with 6g should
also work with gccgo.  Right now cgo has no gccgo
support.

The runtime linkage between Go and C is obviously
easier in gccgo than in 6g.  The benefit of cgo in
the gccgo context is mainly the nice wrapping and
being able to build the same code in both 
environments.

[lvdlvd]

Comment 1:

Labels changed: added cgo, gccgo.

Owner changed to @lvdlvd.

[rsc]

Comment 2:

Labels changed: added priority-later, removed priority-medium.

[rsc]

Comment 3:

Labels changed: added priority-go1.

[lvdlvd]

Comment 4:

http://code.google.com/p/go/source/detail?r=f0a9767e7569

[robpike]

Comment 5:

Owner changed to builder@golang.org.

[rsc]

Comment 6:

Remy, Ian: is this done?

[remyoudompheng]

Comment 7:

I don't think so: it is missing a cgocall equivalent (is it a goal?) and support for
exports, and double returns for errno's.

[remyoudompheng]

Comment 8:

Unsurprisingly, the Go-SDL (github.com/banthar/Go-SDL/sdl) example program compiles but
crashes with gccgo, libX11 wants a huge stack at some point.

[rsc]

Comment 9:

Labels changed: added go1-must.

[rsc]

Comment 10:

Is this implemented now, and working except for reported bugs?
If so, let's close this one.

[remyoudompheng]

Comment 11:

Still missing the  supprt for exports. I don't know how to do it. I think it requires
cgo to have the knowledge of what symbols the Go functions will get, and use
void goCallback() __asm__("the_symbol_of_the_go_callback"); 
in C generated code. But last time I tried i got an undefined symbol.

[ianlancetaylor]

Comment 12:

It should work if you use the right symbol name.  See
http://tip.golang.org/doc/install/gccgo#Function_names .  Don't ask about method names,
but presumably you aren't going to try to call them anyhow.

[minux]

Comment 13:

Issue #3183 has been merged into this issue.

[remyoudompheng]

Comment 14:

Now it misses:
* support for global variables (issue #3183)
* calling of inline functions (issue #3027)
* export of methods
* export of unexported functions (probably not going to happen?)

[alberts]

Comment 15:

I've also filed issue #3332 with a few more problems.