[ruby-core:46496] Re: pkg-config on aix

On Jul 14, 2012, at 4:58 PM, Perry Smith wrote:

> I put pkg-config back into my path and tried to build ruby.  I'm building ruby-1.9.3-p194 on AIX 6100-07-03-1207.   The configure pass ends with this error:
> 
>> Variable 'TARGET' not defined in './ruby.tmp.pc'
> 
> 
> The ruby.tmp.pc file for AIX ends up with this line:
> 
>> DLDFLAGS=-eInit_${TARGET}
> 
> 
> This is related to the other question(s) I had but in this case, I don't see a way to fix this at all.  I don't know pkg-config much but I'm not seeing a way to get target dependent variables into the pkg-config .pc file.
> 
> I moved up to pkg-config 0.27. I tried 0.25 before with the same result.
> 
> I tried not using pkg-config but when I try to build a ruby extension, (event machine in this case), the mkmf is confused.  It is doing a static link but looking for the shared library -lruby.  In that case, ld will look for libruby.a but there is not one.  I could create one by hand but I'm trying to understand the direction the ruby project is trying to take.
> 
> So that is why I decided to put pkg-config back into my path and see if I can make it work that way.  But, so far, I can't.
> 
> I got shared libraries working with ruby 1.9.2 but all those tricks are not working with 1.9.3 at this point.
> 
> Can someone help me understand how this is intended to work?

Here are three alternatives to approach / fix this issue:

A prefix: TARGET changes to TARGET_NAME depending upon which version / patches of ruby you have.  But, lets just stick with TARGET for this example.
=========
First approach:

Add this to ruby.pc:

TARGET=TARGET

Now, this passes:

PKG_CONFIG_PATH=. pkg-config --print-errors ruby.tmp

and to use it, people can do:

PKG_CONFIG_PATH=. pkg-config --define-variable=TARGET=foo --libs ruby.tmp

which gives:

-eInit_foo -L/usr/local/lib -lruby -lpthread -lrt -ldl -lcrypt -lm  
=========
Second approach:

Leave out the TARGET=TARGET line and call pkg-config in config.status this way:

PKG_CONFIG_PATH=. pkg-config --define-variable=TARGET=foo --print-errors ruby.tmp

The call to pkg-config would be the same as the first approach.  This is nice because now calling pkg-config without defining TARGET fails instead of producing a worthless output.

e.g.

PKG_CONFIG_PATH=. pkg-config --libs ruby.tmp

produces:

Variable 'TARGET' not defined in './ruby.tmp.pc'

and an exit status of 1.  I think this is my favorite.
=========
Third approach:

Change this line:

DLDFLAGS=-eInit_${TARGET}

to

DLDFLAGS=-eInit_$(TARGET)

Now this passes:

PKG_CONFIG_PATH=. pkg-config --print-errors ruby.tmp

The normal ussage call:

PKG_CONFIG_PATH=. pkg-config --libs ruby.tmp

produces:

-eInit_$(TARGET) -L/usr/local/lib -lruby -lpthread -lrt -ldl -lcrypt -lm

With radical Makefile gymnastics such as (foo.mk)
---------
TARGET=foo
$(eval F=$(shell PKG_CONFIG_PATH=. pkg-config --libs ruby.tmp) )

all:
        @echo $(F)
---------
The command:

make -f foo.mk

produces:

-eInit_foo -L/usr/local/lib -lruby -lpthread -lrt -ldl -lcrypt -lm
=========

None of these 100% conforms to standard pkg-config usage which is where I start to get confused again.  Ruby has the tradition of extconf.rb using mkmr.rb and that does not need to use pkg-config for this part of the processing.  I'm not clear what the final goal is.

I hope this helps someone...

Perry