@@ -258,5 +258,147 @@
 		], [
 			AC_MSG_RESULT([not found])
 		]
 	)
 ])
+
+dnl Usage:
+dnl    DC_TEST_SHOBJFLAGS(shobjflags, shobjldflags, action-if-not-found)
+dnl
+AC_DEFUN(DC_TEST_SHOBJFLAGS, [
+  AC_SUBST(SHOBJFLAGS)
+  AC_SUBST(SHOBJLDFLAGS)
+
+  OLD_LDFLAGS="$LDFLAGS"
+  SHOBJFLAGS=""
+
+  LDFLAGS="$OLD_LDFLAGS $1 $2"
+
+  AC_TRY_LINK([#include <stdio.h>
+int unrestst(void);], [ printf("okay\n"); unrestst(); return(0); ], [ SHOBJFLAGS="$1"; SHOBJLDFLAGS="$2" ], [
+  LDFLAGS="$OLD_LDFLAGS"
+  $3
+])
+
+  LDFLAGS="$OLD_LDFLAGS"
+])
+
+AC_DEFUN(DC_GET_SHOBJFLAGS, [
+  AC_SUBST(SHOBJFLAGS)
+  AC_SUBST(SHOBJLDFLAGS)
+
+  AC_MSG_CHECKING(how to create shared objects)
+
+  if test -z "$SHOBJFLAGS" -a -z "$SHOBJLDFLAGS"; then
+    DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -rdynamic], [
+      DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared], [
+        DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -rdynamic -mimpure-text], [
+          DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -mimpure-text], [
+            DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -rdynamic -Wl,-G,-z,textoff], [
+              DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -Wl,-G,-z,textoff], [
+                DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-shared -dynamiclib -flat_namespace -undefined suppress -bind_at_load], [
+                  DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-dynamiclib -flat_namespace -undefined suppress -bind_at_load], [
+                    DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-Wl,-dynamiclib -Wl,-flat_namespace -Wl,-undefined,suppress -Wl,-bind_at_load], [
+                      DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-dynamiclib -flat_namespace -undefined suppress], [
+                        DC_TEST_SHOBJFLAGS([-fPIC -DPIC], [-dynamiclib], [
+                          AC_MSG_RESULT(cant)
+                          AC_MSG_ERROR([We are unable to make shared objects.])
+                        ])
+                      ])
+                    ])
+                  ])
+                ])
+              ])
+            ])
+          ])
+        ])
+      ])
+    ])
+  fi
+
+  AC_MSG_RESULT($SHOBJLDFLAGS $SHOBJFLAGS)
+])
+
+AC_DEFUN(DC_CHK_OS_INFO, [
+	AC_CANONICAL_HOST
+	AC_SUBST(SHOBJEXT)
+	AC_SUBST(AREXT)
+        AC_SUBST(SHOBJFLAGS)
+        AC_SUBST(SHOBJLDFLAGS)
+
+        AC_MSG_CHECKING(host operating system)
+        AC_MSG_RESULT($host_os)
+
+	SHOBJEXT="so"
+	AREXT="a"
+
+        case $host_os in
+                darwin*)
+			SHOBJEXT="dylib"
+                        ;;
+		hpux*)
+			SHOBJEXT="sl"
+			;;
+		mingw*)
+			SHOBJEXT="dll"
+			SHOBJFLAGS="-mno-cygwin -mms-bitfields -DPIC"
+			SHOBJLDFLAGS='-shared -Wl,--dll -Wl,--enable-auto-image-base -Wl,--output-def,$[@].def,--out-implib,$[@].a -Wl,--export-all-symbols -Wl,--add-stdcall-alias'
+			;;
+	esac
+])
+
+AC_DEFUN(DC_TEST_WHOLE_ARCHIVE_SHARED_LIB, [
+
+	SAVE_LIBS="${LIBS}"
+
+	LIBS="${WHOLEARCHIVE} $1 ${NOWHOLEARCHIVE} ${SAVE_LIBS}"
+	AC_LINK_IFELSE(
+		AC_LANG_PROGRAM([[
+			]], [[
+			]]
+		),
+		[
+			LIBS="${SAVE_LIBS}"
+
+			$2
+		], [
+			LIBS="${SAVE_LIBS}"
+
+			$3
+		]
+	)
+])
+
+AC_DEFUN(DC_CHECK_FOR_WHOLE_ARCHIVE, [
+	AC_MSG_CHECKING([for how to link whole archive])
+
+	SAVE_CFLAGS="${CFLAGS}"
+
+	wholearchive=""
+
+	for check in "-Wl,--whole-archive -Wl,--no-whole-archive" "-Wl,-z,allextract -Wl,-z,defaultextract"; do
+		CFLAGS="${SAVE_CFLAGS} ${check}"
+
+		AC_LINK_IFELSE(AC_LANG_PROGRAM([], []),
+			[
+				wholearchive="${check}"
+
+				break
+			]
+		)
+
+	done
+
+	CFLAGS="${SAVE_CFLAGS}"
+
+	if test -z "${wholearchive}"; then
+		AC_MSG_RESULT([not found])
+	else
+		AC_MSG_RESULT([${wholearchive}])
+
+		WHOLEARCHIVE=`echo "${wholearchive}" | cut -f 1 -d ' '`
+		NOWHOLEARCHIVE=`echo "${wholearchive}" | cut -f 2 -d ' '`
+	fi
+
+	AC_SUBST(WHOLEARCHIVE)
+	AC_SUBST(NOWHOLEARCHIVE)
+])