$OpenBSD: patch-src_tools_c,v 1.3 2014/03/15 09:13:13 benoit Exp $
--- src/tools.c.orig	Fri Aug 14 14:53:11 2009
+++ src/tools.c	Sun Oct 24 10:56:43 2010
@@ -13,13 +13,42 @@ void _ntl_abort_cxx_callback(void)
 }
 
 
+#include <cstdio>
+
 NTL_START_IMPL
 
 void (*ErrorCallback)() = 0;
 
 
+/*
+   The following code differs from vanilla NTL 5.4.2.
+
+   We add a SetErrorCallbackFunction(). This sets a global callback function _function_,
+   which gets called with parameter _context_ and an error message string whenever Error()
+   gets called.
+
+   Note that if the custom error handler *returns*, then NTL will dump the error message
+   back to stderr and abort() as it habitually does.
+
+   -- David Harvey (2008-04-12)
+*/
+
+void (*ErrorCallbackFunction)(const char*, void*) = NULL;
+void *ErrorCallbackContext = NULL;
+
+
+void SetErrorCallbackFunction(void (*function)(const char*, void*), void *context)
+{
+   ErrorCallbackFunction = function;
+   ErrorCallbackContext = context;
+}
+
+
 void Error(const char *s)
 {
+   if (ErrorCallbackFunction != NULL)
+      ErrorCallbackFunction(s, ErrorCallbackContext);
+
    cerr << s << "\n";
    _ntl_abort();
 }
