[MacPorts] #57009: ImageMagick @6.9.9-40_1: inserts -lgomp into pkgconfig files, which breaks build when using clang

[MacPorts]

#57009: ImageMagick @6.9.9-40_1: inserts -lgomp into pkgconfig files, which breaks
build when using clang
--------------------------+------------------------
  Reporter:  kencu        |      Owner:  ryandesign
      Type:  defect       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  ImageMagick  |
--------------------------+------------------------

Comment (by kencu):

 I think you found a good clue to the issue. That
 [https://github.com/ImageMagick/ImageMagick6/commit/7a8c2e5471b0595f1dcc1c8c6d3923919d566f8a
 commit] results in this block in configure.ac.
 {{{
 #
 # Find OpenMP library
 #
 GOMP_LIBS=''
 if test "$enable_openmp" != 'no'; then
   if test "${GCC}" = "yes"; then
     # Open64 (passes for GCC but uses different OpenMP implementation)
     if test "x$GOMP_LIBS" = x ; then
       if $CC --version 2>&1 | grep Open64 > /dev/null ; then
         AC_CHECK_LIB(openmp,omp_get_num_procs,GOMP_LIBS="-lopenmp",,)
       fi
     fi
     # Clang (passes for GCC but uses different OpenMP implementation)
     if test "x$LIB_OMP" = x ; then
       if $CC --version 2>&1 | grep clang > /dev/null ; then
         AC_CHECK_LIB(omp,GOMP_parallel_start,LIB_OMP="-lomp",,)
       fi
     fi
     # GCC
     if test "x$GOMP_LIBS" = x ; then
       AC_CHECK_LIB(gomp,GOMP_parallel_start,GOMP_LIBS="-lgomp",,)
     fi
   else
     # Sun CC
     if test "x$GOMP_LIBS" = x ; then
       AC_CHECK_LIB(mtsk,sunw_mp_register_warn,GOMP_LIBS="-lmtsk",,)
     fi
     # AIX xlc
     if test "x$GOMP_LIBS" = x ; then
     AC_CHECK_LIB(xlsmp,_xlsmpFlush,GOMP_LIBS="-lxlsmp",,)
     fi
     # SGI IRIX 6.5 MIPSpro C/C++
     if test "x$GOMP_LIBS" = x ; then
     AC_CHECK_LIB(mp,mp_destroy,GOMP_LIBS="-lmp",,)
     fi
   fi
   LIBS="$GOMP_LIBS $LIBS"
 fi
 AC_SUBST(GOMP_LIBS)
 }}}
 on my system, both tests pass
 {{{
 configure:30053: checking for GOMP_parallel_start in -lomp
 configure:30078: /opt/local/bin/clang-mp-5.0 -o conftest  -fopenmp -pipe
 -Os -arch x86_64 -Wall -mtune=westmere -fexceptions -D_FORTIFY_SOURCE=0
 -pthread -DMAGICKCORE_HDRI_ENABLE=0 -DMAGICKCORE_QUANTUM_DEPTH=16
 -I/opt/local/include -DMAGICKCORE_HDRI_ENABLE=0
 -DMAGICKCORE_QUANTUM_DEPTH=16 -L/opt/local/lib
 -Wl,-headerpad_max_install_names -arch x86_64 conftest.c -lomp  -lm    >&5
 configure:30078: $? = 0
 configure:30087: result: yes
 configure:30097: checking for GOMP_parallel_start in -lgomp
 configure:30122: /opt/local/bin/clang-mp-5.0 -o conftest  -fopenmp -pipe
 -Os -arch x86_64 -Wall -mtune=westmere -fexceptions -D_FORTIFY_SOURCE=0
 -pthread -DMAGICKCORE_HDRI_ENABLE=0 -DMAGICKCORE_QUANTUM_DEPTH=16
 -I/opt/local/include -DMAGICKCORE_HDRI_ENABLE=0
 -DMAGICKCORE_QUANTUM_DEPTH=16 -L/opt/local/lib
 -Wl,-headerpad_max_install_names -arch x86_64 conftest.c -lgomp  -lm
 >&5
 configure:30122: $? = 0
 configure:30131: result: yes
 }}}
 First of all I'm not at this moment sure how my `clang-5.0` links with
 `-lgomp` during this test, but fails when I'm trying to build `virtuoso-7`
 with that link flag. But that aside, it seems like the configure.ac bit
 completely ignores whether the `-lomp` test passes or not -- it just
 inserts the `GOMP_LIBS` into the link libs no matter what.

 And so `-lgomp` gets passed along forever more as one of the required
 `link libs`, even though `-lomp` worked.

 Let me check if they fixed this in the newer versions of ImageMagick.

-- 
Ticket URL: <https://trac.macports.org/ticket/57009#comment:3>
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