AC_DEFUN([DISPATCH_C_BLOCKS], [
#
# Allow configure to be passed a path to the directory where it should look
# for the Blocks runtime library, if any.
#
AC_ARG_WITH([blocks-runtime],
  [AS_HELP_STRING([--with-blocks-runtime],
    [Specify path to the blocks runtime])],
  [blocks_runtime=${withval}
    LIBS="$LIBS -L$blocks_runtime"]
)

#
# Configure argument to enable/disable using an embedded blocks runtime
#
AC_ARG_ENABLE([embedded_blocks_runtime],
  [AS_HELP_STRING([--enable-embedded-blocks-runtime],
    [Embed blocks runtime in libdispatch [default=yes on Linux, default=no on all other platforms]])],,
  [case $target_os in
      linux*)
        enable_embedded_blocks_runtime=yes
	    ;;
      *)
        enable_embedded_blocks_runtime=no
   esac]
)

#
# Detect compiler support for Blocks; perhaps someday -fblocks won't be
# required, in which case we'll need to change this.
#
AC_CACHE_CHECK([for C Blocks support], [dispatch_cv_cblocks], [
  saveCFLAGS="$CFLAGS"
  CFLAGS="$CFLAGS -fblocks"
  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[(void)^{int i; i = 0; }();])], [
    CFLAGS="$saveCFLAGS"
    dispatch_cv_cblocks="-fblocks"
  ], [
    CFLAGS="$saveCFLAGS"
    dispatch_cv_cblocks="no"
  ])
])

AS_IF([test "x$dispatch_cv_cblocks" != "xno"], [
    CBLOCKS_FLAGS="$dispatch_cv_cblocks"

	AS_IF([test "x$enable_embedded_blocks_runtime" != "xyes"], [
	    #
	    # It may be necessary to directly link the Blocks runtime on some
	    # systems, so give it a try if we can't link a C program that uses
	    # Blocks.  We will want to remove this at somepoint, as really -fblocks
	    # should force that linkage already.
	    #
	    saveCFLAGS="$CFLAGS"
	    CFLAGS="$CFLAGS -fblocks -O0"
	    AC_MSG_CHECKING([whether additional libraries are required for the Blocks runtime])
	    AC_TRY_LINK([], [
		^{ int j; j=0; }();
	    ], [
		AC_MSG_RESULT([no]);
	    ], [
	      saveLIBS="$LIBS"
	      LIBS="$LIBS -lBlocksRuntime"
	      AC_TRY_LINK([], [
		^{ int k; k=0; }();
	      ], [
		AC_MSG_RESULT([-lBlocksRuntime])
	      ], [
		AC_MSG_ERROR([can't find Blocks runtime])
	      ])
	    ])
	])
    CFLAGS="$saveCFLAGS"
    have_cblocks=true
], [
    CBLOCKS_FLAGS=""
    have_cblocks=false
])
AM_CONDITIONAL(HAVE_CBLOCKS, $have_cblocks)
AC_SUBST([CBLOCKS_FLAGS])
AM_CONDITIONAL([BUILD_OWN_BLOCKS_RUNTIME], [test "x$enable_embedded_blocks_runtime" = "xyes"])

#
# Because a different C++ compiler may be specified than C compiler, we have
# to do it again for C++.
#
AC_LANG_PUSH([C++])
AC_CACHE_CHECK([for C++ Blocks support], [dispatch_cv_cxxblocks], [
  saveCXXFLAGS="$CXXFLAGS"
  CXXFLAGS="$CXXFLAGS -fblocks"
  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[(void)^{int i; i = 0; }();])], [
    CXXFLAGS="$saveCXXFLAGS"
    dispatch_cv_cxxblocks="-fblocks"
  ], [
    CXXFLAGS="$saveCXXFLAGS"
    dispatch_cv_cxxblocks="no"
  ])
])

AS_IF([test "x$dispatch_cv_cxxblocks" != "xno"], [
    CXXBLOCKS_FLAGS="$dispatch_cv_cxxblocks"

	AS_IF([test "x$enable_embedded_blocks_runtime" != "xyes"], [
	    saveCXXFLAGS="$CXXFLAGS"
	    CXXFLAGS="$CXXFLAGS -fblocks -O0"
	    AC_MSG_CHECKING([whether additional libraries are required for the Blocks runtime])
	    AC_TRY_LINK([], [
		^{ int j; j=0; }();
	    ], [
		AC_MSG_RESULT([no]);
	    ], [
	      saveLIBS="$LIBS"
	      LIBS="$LIBS -lBlocksRuntime"
	      AC_TRY_LINK([], [
		^{ int k; k=0; }();
	      ], [
		AC_MSG_RESULT([-lBlocksRuntime])
	      ], [
		AC_MSG_ERROR([can't find Blocks runtime])
	      ])
	    ])
	])
    CXXFLAGS="$saveCXXFLAGS"
    have_cxxblocks=true
], [
    CXXBLOCKS_FLAGS=""
    have_cxxblocks=false
])
AC_LANG_POP([C++])
AM_CONDITIONAL(HAVE_CXXBLOCKS, $have_cxxblocks)
AC_SUBST([CXXBLOCKS_FLAGS])
])