[MacPorts] #30370: libpixman erroneous execution with llvm-gcc-4.2

[MacPorts]

#30370: libpixman erroneous execution with llvm-gcc-4.2
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  Reporter:  ejtttje@…          |       Owner:  ryandesign@…               
      Type:  defect             |      Status:  reopened                   
  Priority:  Normal             |   Milestone:                             
 Component:  ports              |     Version:  2.0.0                      
Resolution:                     |    Keywords:  lion llvm-gcc-4.2 cairo pdf
      Port:  libpixman          |  
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Comment(by ejtttje@…):

 Yes, libpixman does do some asm, which is the root cause of the issue...
 must be making some assumptions about how the compiler is going to emit
 code, and is noted as a source of issues when moving to llvm.  Older
 versions of clang have additional parsing bugs, some of which I ran into
 in my own code (and to their credit, the clang team was responsive to my
 bug reports and I moved pretty easily to svn checkout of clang to use
 their fixes.)

 So, really MacPorts should do a version test on the compiler to make the
 selection: users could have retained an old Xcode 3 install through a Lion
 upgrade, or inversely, be on Snow Leopard but updated the clang install
 like I did.  So it would be more robust to base the selection on the
 available clang version instead of the OS version.  For reference:
  * a semi-recent manual build from llvm/clang svn reports --version "clang
 version 3.0 (trunk 129294)"
  * the Xcode 4.1 version reports as "Apple clang version 2.1
 (tags/Apple/clang-163.7.1) (based on LLVM 3.0svn)"
  * Xcode 4.0 was "based on LLVM 2.9svn"

 I'd suggest requiring clang>=3.0 in order to be robust.  But more
 practically, don't worry about it and just fall back to gcc-4.2 for
 everyone for now :)

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Ticket URL: <https://trac.macports.org/ticket/30370#comment:5>
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