[MacPorts] #38768: atlas: use compiler_blacklist_versions portgroup

[MacPorts]

#38768: atlas: use compiler_blacklist_versions portgroup
--------------------------+---------------------
 Reporter:  ryandesign@…  |      Owner:  vince@…
     Type:  enhancement   |     Status:  new
 Priority:  Normal        |  Milestone:
Component:  ports         |    Version:  2.1.3
 Keywords:                |       Port:  atlas
--------------------------+---------------------
 The atlas port has this block of code in the +clang variant:

 {{{
     if {[vercmp $xcodeversion 4.3] < 0} {
         pre-fetch {
             return -code error "Your version of clang is too old!"
         }
     }
 }}}

 This is not the correct way to check for this. You need to check the clang
 version, not the Xcode version, because the user could have updated Xcode
 but forgotten to update the command line tools; this happens all the time
 because users do not know that they need to actually open the Xcode
 application in order for the command line tools to get updated.

 Use the
 [browser:trunk/dports/_resources/port1.0/group/compiler_blacklist_versions-1.0.tcl
 compiler_blacklist_versions] portgroup to blacklist the specific range of
 Xcode clang versions that will not work for atlas. If the clang is older,
 then MacPorts will use llvm-gcc-4.2 instead. XcodeVersionInfo lists some
 known clang versions.

 It's odd to have a +clang variant at all and it seems like you could
 remove it. MacPorts will automatically choose to use clang on Xcode 4.2
 and later anyway.

-- 
Ticket URL: <https://trac.macports.org/ticket/38768>
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