[MacPorts] #55733: lz4 fails to build on Snow Leopard

[MacPorts]

#55733: lz4 fails to build on Snow Leopard
-------------------------+---------------------------------------
  Reporter:  grumpybozo  |      Owner:
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.4.2
Resolution:              |   Keywords:  haspatch snowleopard i386
      Port:  lz4         |
-------------------------+---------------------------------------

Comment (by kencu):

 By the way, although it's certainly great to fix up these ports one by one
 to send the right `-stdlib` to the compiler, the reason they stay broken
 for so long is that nobody on newer systems would ever notice this.

 So if you ever get tired of fixing this particular issue on these older
 systems, it's really quite easy to change clang on your system to return
 the default `stdlib` you want (in your case, you want it to default to
 libc++). There is one function found in each version of clang that
 controls this. For clang-5.0 it lives here in:
 {{{
 tools/clang/lib/Driver/ToolChains/Darwin.cpp
 }}}

 {{{
 ToolChain::CXXStdlibType Darwin::GetDefaultCXXStdlibType() const {
   // Default to use libc++ on OS X 10.9+ and iOS 7+.
   if ((isTargetMacOS() && !isMacosxVersionLT(10, 9)) ||
        (isTargetIOSBased() && !isIPhoneOSVersionLT(7, 0)) ||
        isTargetWatchOSBased())
     return ToolChain::CST_Libcxx;

   return ToolChain::CST_Libstdcxx;
 }
 }}}

 I just change that
 {{{
 if ((isTargetMacOS() && !isMacosxVersionLT(10, 9))
 }}}
 to
 {{{
 if ((isTargetMacOS() && !isMacosxVersionLT(10, 4))
 }}}

 and then you get `-stdlib=libc++` added by default on all systems, which
 is what you want.

--
Ticket URL: <https://trac.macports.org/ticket/55733#comment:2>
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