[MacPorts] #34233: apple-gcc42 doesn't honor -isysroot correctly

[MacPorts]

#34233: apple-gcc42 doesn't honor -isysroot correctly
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 Reporter:  jeremyhu@…             |       Owner:  royliu@…           
     Type:  defect                 |      Status:  new                
 Priority:  Normal                 |   Milestone:                     
Component:  ports                  |     Version:  2.0.4              
 Keywords:                         |        Port:  apple-gcc42        
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Comment(by royliu@…):

 I'm still not understanding how my patch made things worse.  There are
 essentially two types of includes that are being addressed.  They look
 like:

 {{{
  /Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2/lib/gcc/i686
 -apple-darwin11/4.2.1/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk/usr/include
 }}}

 I think the problem arises when Apple provides default compilers.  These
 default compilers are installed in the default prefix, i.e., `/usr`.
 Apple also provides SDKs which serve as sysroots.  A sysroot is a self-
 contained, alternate include hierarchy.  Naturally, the internal structure
 of Apple SDKs use the `/usr` hierarchy to mirror their compiler
 installations, and it's all good.  The MacPorts compiler is installed in
 `/opt/local`, and third party libraries are asking for `-isysroot` to be
 set to an Apple-provided SDK which uses the `/usr` hierarchy.  This is the
 crux of the problem.  The patch I made attempts to address the above two
 cases.  In the first case, the include directory is compiler-specific, and
 so we actually want the MacPorts compiler's hierarchy, and drop the
 sysroot.  In the second case, the user's intention is to use a "default"
 set of includes provided by the SDK.  The best way I can think of is to:

   1. Ignore `sysroot` for the compiler's include directory (the MacPorts
 compiler directory being invariant over SDKs).
   2. Overwrite `/opt/local/include` with `/usr/include` when `sysroot` is
 about to be prepended, since that is what your vanilla Apple-provided
 compiler has access to.

 Is this set of policies what you had in mind?  If not, what should be the
 correct set of includes for a MacPorts compiler when `-isysroot` is
 specified?  If so, then can you give a case where my patch isn't correct?

-- 
Ticket URL: <https://trac.macports.org/ticket/34233#comment:16>
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