code review 4287056: Make.pkg: add support for SWIG, and add two SWIG examples

Make.pkg: add support for SWIG, and add two SWIG examples

The SWIG examples are not yet built or tested by default.

[iant, 2011-03-17 02:56:24]

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

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2011-03-17 05:26:32]

LGTM

http://codereview.appspot.com/4287056/diff/4001/misc/swig/callback/run.go
File misc/swig/callback/run.go (right):

http://codereview.appspot.com/4287056/diff/4001/misc/swig/callback/run.go#new...
misc/swig/callback/run.go:8: "swig/callback"
sort

http://codereview.appspot.com/4287056/diff/4001/src/Make.pkg
File src/Make.pkg (right):

http://codereview.appspot.com/4287056/diff/4001/src/Make.pkg#newcode48
src/Make.pkg:48: INSTALLFILES+=$(patsubst
%.swig,$(pkgdir)/$(dir)/%.so,$(patsubst %.swigcxx,%.swig,$(SWIGFILES)))
What do we need to do to get rid of these?
When cgo installed these kinds of things it 
did it to a path without /s in them so that
the usual relative lookup could find them
after being copied elsewhere.  Do we need to
worry about that here?

http://codereview.appspot.com/4287056/diff/4001/src/Make.pkg#newcode119
src/Make.pkg:119: ifneq ($(CGOFILES)$(SWIGFILES),)
:-)

http://codereview.appspot.com/4287056/diff/4001/src/Make.pkg#newcode195
src/Make.pkg:195: #	SWIGFILES=myclib.swig mycxxlib.swigcxx
add
#
# Packages using the resulting binary will refer to
# $(pkgdir)/$target.so and will need that shared object
# at run time.

[iant2, 2011-03-17 15:52:20]

rsc@golang.org writes:

> http://codereview.appspot.com/4287056/diff/4001/src/Make.pkg#newcode48
> src/Make.pkg:48: INSTALLFILES+=$(patsubst
> %.swig,$(pkgdir)/$(dir)/%.so,$(patsubst %.swigcxx,%.swig,$(SWIGFILES)))
> What do we need to do to get rid of these?

We need to have a linker which can fully support C++.  I think the
simpler long-term path going forward will be to be to have 6l/8l emit an
ELF .o file, and complete the link using ld/.  The cost is a two stage
link process when using SWIG.  Alternatively we have to teach 6l/8l
about linker scripts, symbol visibility, versioning, and .init section
sorting, all of which is possible but I think more work.

I know less about Mach-O though the basic idea of emitting a Mach-O .o
file will work too.


> When cgo installed these kinds of things it
> did it to a path without /s in them so that
> the usual relative lookup could find them
> after being copied elsewhere.  Do we need to
> worry about that here?

Unless I misunderstand I think we're OK.  We put a simple name, not a
path, in the DT_NEEDED tag in the executable, so if you move the shared
library you can set LD_LIBRARY_PATH and the executable will find it.
It's not perfect but it's workable.

Ian

[rsc, 2011-03-17 16:11:45]

> Unless I misunderstand I think we're OK.  We put a simple name, not a
> path, in the DT_NEEDED tag in the executable, so if you move the shared
> library you can set LD_LIBRARY_PATH and the executable will find it.
> It's not perfect but it's workable.

I looked again.  It looks like the name is foo, so if there are two
different packages x/foo and y/foo they will both refer to foo.so.
Is that true?  I think cgo, before it stopped using shared libraries,
referred to x_foo.so and y_foo.so, but I might be misremembering.

Russ

[r, 2011-03-18 00:22:34]

LGTM

[iant2, 2011-03-21 21:16:31]

Russ Cox <rsc@golang.org> writes:

>> Unless I misunderstand I think we're OK.  We put a simple name, not a
>> path, in the DT_NEEDED tag in the executable, so if you move the shared
>> library you can set LD_LIBRARY_PATH and the executable will find it.
>> It's not perfect but it's workable.
>
> I looked again.  It looks like the name is foo, so if there are two
> different packages x/foo and y/foo they will both refer to foo.so.
> Is that true?  I think cgo, before it stopped using shared libraries,
> referred to x_foo.so and y_foo.so, but I might be misremembering.

Good point.  Fixed to include the full target name in the .so name.

PTAL.

Ian

[rsc, 2011-03-22 18:32:51]

LGTM

[iant, 2011-03-22 20:06:03]

*** Submitted as http://code.google.com/p/go/source/detail?r=53d99c6f0ef8 ***

Make.pkg: add support for SWIG, and add two SWIG examples

The SWIG examples are not yet built or tested by default.

R=r, rsc, iant2
CC=golang-dev
http://codereview.appspot.com/4287056