+dnl CF_FIND_LINKAGE version: 13 updated: 2008/12/24 07:59:55
+dnl ---------------
+dnl Find a library (specifically the linkage used in the code fragment),
+dnl searching for it if it is not already in the library path.
+dnl See also CF_ADD_SEARCHPATH.
+dnl
+dnl Parameters (4-on are optional):
+dnl $1 = headers for library entrypoint
+dnl $2 = code fragment for library entrypoint
+dnl $3 = the library name without the "-l" option or ".so" suffix.
+dnl $4 = action to perform if successful (default: update CPPFLAGS, etc)
+dnl $5 = action to perform if not successful
+dnl $6 = module name, if not the same as the library name
+dnl $7 = extra libraries
+dnl
+dnl Sets these variables:
+dnl $cf_cv_find_linkage_$3 - yes/no according to whether linkage is found
+dnl $cf_cv_header_path_$3 - include-directory if needed
+dnl $cf_cv_library_path_$3 - library-directory if needed
+dnl $cf_cv_library_file_$3 - library-file if needed, e.g., -l$3
+AC_DEFUN([CF_FIND_LINKAGE],[
+
+# If the linkage is not already in the $CPPFLAGS/$LDFLAGS configuration, these
+# will be set on completion of the AC_TRY_LINK below.
+cf_cv_header_path_$3=
+cf_cv_library_path_$3=
+
+CF_MSG_LOG([Starting [FIND_LINKAGE]($3,$6)])
+
+AC_TRY_LINK([$1],[$2],
+ cf_cv_find_linkage_$3=yes,[
+ cf_cv_find_linkage_$3=no
+
+ CF_VERBOSE(find linkage for $3 library)
+ CF_MSG_LOG([Searching for headers in [FIND_LINKAGE]($3,$6)])
+
+ cf_save_CPPFLAGS="$CPPFLAGS"
+ cf_test_CPPFLAGS="$CPPFLAGS"
+
+ CF_HEADER_PATH(cf_search,ifelse([$6],,[$3],[$6]))
+ for cf_cv_header_path_$3 in $cf_search
+ do
+ if test -d $cf_cv_header_path_$3 ; then
+ CF_VERBOSE(... testing $cf_cv_header_path_$3)
+ CPPFLAGS="$cf_save_CPPFLAGS -I$cf_cv_header_path_$3"
+ AC_TRY_COMPILE([$1],[$2],[
+ CF_VERBOSE(... found $3 headers in $cf_cv_header_path_$3)
+ cf_cv_find_linkage_$3=maybe
+ cf_test_CPPFLAGS="$CPPFLAGS"
+ break],[
+ CPPFLAGS="$cf_save_CPPFLAGS"
+ ])
+ fi
+ done
+
+ if test "$cf_cv_find_linkage_$3" = maybe ; then
+
+ CF_MSG_LOG([Searching for $3 library in [FIND_LINKAGE]($3,$6)])
+
+ cf_save_LIBS="$LIBS"
+ cf_save_LDFLAGS="$LDFLAGS"
+
+ ifelse([$6],,,[
+ CPPFLAGS="$cf_test_CPPFLAGS"
+ LIBS="-l$3 $7 $cf_save_LIBS"
+ AC_TRY_LINK([$1],[$2],[
+ CF_VERBOSE(... found $3 library in system)
+ cf_cv_find_linkage_$3=yes])
+ CPPFLAGS="$cf_save_CPPFLAGS"
+ LIBS="$cf_save_LIBS"
+ ])
+
+ if test "$cf_cv_find_linkage_$3" != yes ; then
+ CF_LIBRARY_PATH(cf_search,$3)
+ for cf_cv_library_path_$3 in $cf_search
+ do
+ if test -d $cf_cv_library_path_$3 ; then
+ CF_VERBOSE(... testing $cf_cv_library_path_$3)
+ CPPFLAGS="$cf_test_CPPFLAGS"
+ LIBS="-l$3 $7 $cf_save_LIBS"
+ LDFLAGS="$cf_save_LDFLAGS -L$cf_cv_library_path_$3"
+ AC_TRY_LINK([$1],[$2],[
+ CF_VERBOSE(... found $3 library in $cf_cv_library_path_$3)
+ cf_cv_find_linkage_$3=yes
+ cf_cv_library_file_$3="-l$3"
+ break],[
+ CPPFLAGS="$cf_save_CPPFLAGS"
+ LIBS="$cf_save_LIBS"
+ LDFLAGS="$cf_save_LDFLAGS"
+ ])
+ fi
+ done
+ LIBS="$cf_save_LIBS"
+ CPPFLAGS="$cf_save_CPPFLAGS"
+ LDFLAGS="$cf_save_LDFLAGS"
+ fi
+
+ else
+ cf_cv_find_linkage_$3=no
+ fi
+ ],$7)
+
+if test "$cf_cv_find_linkage_$3" = yes ; then
+ifelse([$4],,[
+ CF_ADD_INCDIR($cf_cv_header_path_$3)
+ CF_ADD_LIBDIR($cf_cv_library_path_$3)
+ LIBS="-l$3 $LIBS"
+],[$4])
+else
+ifelse([$5],,AC_MSG_WARN(Cannot find $3 library),[$5])
+fi
+])dnl
+dnl ---------------------------------------------------------------------------