testing the value of ${CXX} in ports Makefile

[Don Lewis]

On 29 Jan, Elizabeth Myers wrote:
> On 01/29/15 21:43, Don Lewis 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.

> Why do you need to detect it? Shouldn't USE_GCC ensure it's there? In
> any case, browsing through the ports tree, you could try .if
> !empty(CXX:M*g++49*)

With USE_GCC=yes, CXX will currently get set to g++48, but at some point
the default version will get upgraded to 4.9.  Unfortunately, that
breaks the port build unless I apply an extra patch to the source.  I
could set USE_GCC=4.8, but once the default version of gcc gets updated,
anyone who uses the port will need both gcc 4.8 for this port and 4.9
for the majority of parts that just use USE_GCC=yes to get the default.

I think your suggestion has the same problem as what I tried.because
when the .if is evaluated, the value of CXX has still not been updated
by bsd.gcc.mk.  It still has the original value set by
/usr/share/mk/sys/mk.