Avoid dlclose() only when valgrind is running

configure.ac

@@ -1565,7 +1565,11 @@ AC_ARG_ENABLE(debug,
 test "${enable_debug}" != "yes" && enable_debug="no"
 AH_TEMPLATE(NDEBUG,
             [Define to 1 if debug code should NOT be compiled])
-AS_IF([test "x${enable_debug}" = "xno"], [AC_DEFINE(NDEBUG)])
+AS_IF([test "x${enable_debug}" = "xno"], [
+  AC_DEFINE(NDEBUG)
+], [
+  AC_CHECK_HEADERS([valgrind/valgrind.h])
+])
 
 dnl
 dnl Allow runing as root (usefull for people runing on embedded platforms)

src/modules/os.c

@@ -65,6 +65,9 @@
 #       include <dl.h>
 #   endif
 #endif
+#ifdef HAVE_VALGRIND_VALGRIND_H
+# include <valgrind/valgrind.h>
+#endif
 
 /*****************************************************************************
  * Local prototypes
@@ -274,11 +277,11 @@ void module_Unload( module_handle_t handle )
     FreeLibrary( handle );
 
 #elif defined(HAVE_DL_DLOPEN)
-# ifdef NDEBUG
-    dlclose( handle );
-# else
-    (void)handle;
+# ifdef HAVE_VALGRIND_VALGRIND_H
+    if( RUNNING_ON_VALGRIND > 0 )
+        return; /* do not dlclose() so that we get proper stack traces */
 # endif
+    dlclose( handle );
 
 #elif defined(HAVE_DL_SHL_LOAD)
     shl_unload( handle );