testing the value of ${CXX} in ports Makefile

[Don Lewis]

On 29 Jan, Chris H wrote:
> On Thu, 29 Jan 2015 19:43:38 -0800 (PST) Don Lewis <truckman at FreeBSD.org> wrote
> 
>> I need to test the value of ${CXX} in the Makefile for a port and am
>> getting unexpected results.  Here is a simplified version of the
>> Makefile:
>> 
>> PORTNAME=    junk
>> PORTVERSION=    0.0.0
>> CATEGORIES=    devel
>> DISTFILES=
>> 
>> MAINTAINER=    truckman at FreeBSD.org
>> COMMENT=    junk
>> 
>> USE_GCC=    4.9+
>> 
>> .include <bsd.port.pre.mk>
>> 
>> post-patch:
>>     echo CXX=${CXX}
>> .if ${CXX} == g++49
>>     echo detected g++49
>> .else
>>     echo did not detect g++49
>> .endif
>> 
>> .include <bsd.port.post.mk>
>> 
>> 
>> If I run "make patch", this is what I get:
>> 
>> # make patch
>> ===>   junk-0.0.0 depends on file: /usr/local/sbin/pkg - found
>> ===> Fetching all distfiles required by junk-0.0.0 for building
>> ===>  Extracting for junk-0.0.0
>> ===>  Patching for junk-0.0.0
>> echo CXX=g++49
>> CXX=g++49
>> echo did not detect g++49
>> did not detect g++49
>> 
>> 
>> If I run "make -dA patch" and look at the debug output, I observe
>> bsd.gcc.mk getting processed after the .if is evaluated.  When the .if
>> is processed, the value of ${CXX} is still c++.  It sort of looks like
>> bsd.gcc.mk isn't getting included until bsd.port.post.mk and we are
>> relying on lazy expansion to get the correct value of ${CXX} for the
>> actions.
>> 
>> It sort of looks like I'll have to do something like:
>> 
>> post-patch:
>>     [ ${CXX} = g++49 ] && echo detected g++49
>> 
>> but that just seems goofy.
> I'm not attempting to come off as any sot of expert. But it
> seems like you're going the long way around. Couldn't you
> just as easily REQUIRE, or perhaps even better; simply reverse
> the logic;
> 
> if ${CXX} != g++49
> @VOMIT
> endif
> 
> It'd be shorter, and still assures the results you require,
> no? Just a thought.

gcc46, gcc47, gcc48, and probably gcc5 (haven't tested that one yet) all
work.  gcc49 requires a source patch.  I just want to be able to set
USE_GCC=yes and not have the port break when the default version of gcc
gets changed to 4.9.

The way that the ports infrastructure is written, it looks like I can't
do the test with a Makefile .if / .endif.  It looks like I have to do it
in the shell code in actions for the target.

Instead of using [ condition ] && do something, I could also write it as
	if [ ${CXX} = g++49 ]; then apply the patch; fi