[MacPorts] #48331: x265 fails to install due to CMAKE_CXX_COMPILER_ID being unset

[MacPorts]

#48331: x265 fails to install due to CMAKE_CXX_COMPILER_ID being unset
-------------------------+-------------------------
  Reporter:  jeremyhu@…  |      Owner:  michaelld@…
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.3.3
Resolution:              |   Keywords:
      Port:  cmake       |
-------------------------+-------------------------

Comment (by ryandesign@…):

 I have reported this problem to the [http://public.kitware.com/pipermail
 /cmake-developers/2015-September/026586.html cmake-developers mailing
 list]. Reproducing the relevant parts of my message here:

 > I found that in CMakeDetermineCompilerId.cmake, cmake compiles a test
 program (CMAKE_DETERMINE_COMPILER_ID_BUILD) which defines certain strings
 that describe the compiler, and then examines the strings in the compiled
 a.out file (CMAKE_DETERMINE_COMPILER_ID_CHECK). If the file contains more
 than one "INFO:compiler[...]" string, cmake assumes something went wrong
 and sets COMPILER_ID_TWICE to 1 which causes the compiler id to be
 forgotten.
 >
 > The problem is that when building universal, the a.out file produced by
 the test will contain multiple copies of the strings -- once for each
 architecture. What the compiler does for you when you use multiple -arch
 flags is to compile the file separately, once for each architecture, then
 glue the separate files together into a single file (using the lipo
 program), so naturally such a file will contain multiple copies of any
 strings. This is not a bug; this is how universal binaries work. The bug
 is that cmake considers this valid condition to be erroneous.
 >
 > Here is an example of the duplicated strings:
 >
 > {{{
 > $ lipo -info build/CMakeFiles/3.3.2/CompilerIdC/a.out
 > Architectures in the fat file:
 work/build/CMakeFiles/3.3.2/CompilerIdC/a.out are: x86_64 i386
 > $ strings -arch all build/CMakeFiles/3.3.2/CompilerIdC/a.out
 > INFO:compiler[AppleClang]
 > INFO:platform[Darwin]
 > INFO:arch[]
 > INFO:compiler_version[00000007.00000000.00000000.07000072]
 > INFO:compiler[AppleClang]
 > INFO:platform[Darwin]
 > INFO:arch[]
 > INFO:compiler_version[00000007.00000000.00000000.07000072]
 > }}}
 >
 > (I know cmake uses its internal FILE(STRINGS) command, not the strings
 program, but I presume they are similar.)
 >
 > I was able to get cmake to correctly identify the compilers even when
 building universal by simply removing the COMPILER_ID_TWICE stuff from
 CMakeDetermineCompilerId.cmake, but perhaps you want something more
 elegant that verifies that if there are multiple definitions of a
 particular info line, all the definitions are the same.

 Before making [attachment:cmake.diff such a change] to the cmake port,
 I'll wait and see if the developers have a better suggestion.

-- 
Ticket URL: <https://trac.macports.org/ticket/48331#comment:5>
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