[MacPorts] #54135: clang-4.0 error building software on 10.6 (or less) due to #include_next <float.h>

[MacPorts]

#54135: clang-4.0 error building software on 10.6 (or less) due to #include_next
<float.h>
-------------------------+-----------------------
 Reporter:  kencu        |      Owner:
     Type:  defect       |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:  SnowLeopard  |       Port:  clang-4.0
-------------------------+-----------------------
 Jeremy identified this bug six months ago or so, but it's still in the
 clang-4.0 source tree.

 <https://bugs.llvm.org//show_bug.cgi?id=31504>


 Gestos (ftp83) recently came across this error
 <https://pastebin.com/dmNJFQKU> while building glib2 with clang-4.0, and
 asked for help:

 {{{
 :info:build In file included from
 /opt/local/libexec/llvm-4.0/bin/../lib/clang/4.0.0/include/float.h:36:
 :info:build /usr/include/float.h:8:15: fatal error: 'float.h' file not
 found
 :info:build #include_next <float.h>
 :info:build               ^~~~~~~~~
 :info:build 1 error generated.
 }}}

 I generated this bit for the Portfile:
 {{{
 platform darwin {
     # float.h broken on clang (file doesn't exist when building llvm only)
     # only for < SnowLeopard
     if {${subport} eq "clang-${llvm_version}" && ${os.major} < 11 } {
         #  https://bugs.llvm.org//show_bug.cgi?id=31504
         patchfiles-append 998-patch-tools-clang-lib-headers-float-fix-
 SL.diff
     }

 }
 }}}
 and this patchfile
 {{{
 --- ./tools/clang/lib/Headers/float.h.orig      2017-05-06
 10:27:32.000000000 -0700
 +++ ./tools/clang/lib/Headers/float.h   2017-05-06 10:28:08.000000000
 -0700
 @@ -31,7 +31,7 @@
   * Also fall back on Darwin to allow additional definitions and
   * implementation-defined values.
   */
 -#if (defined(__APPLE__) || (defined(__MINGW32__) || defined(_MSC_VER)))
 && \
 +#if ((defined(__MINGW32__) || defined(_MSC_VER))) && \
      __STDC_HOSTED__ && __has_include_next(<float.h>)
  #  include_next <float.h>
  }}}

 and with this I've had no such issues so far building ports with clang-4.0
 on SnowLeopard.

 I hesitate to generate a PR for such a complex port as clang-4.0.

--
Ticket URL: <https://trac.macports.org/ticket/54135>
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