diff -p -up ntl-5.5.2/include/NTL/tools.h.orig ntl-5.5.2/include/NTL/tools.h
--- ntl-5.5.2/include/NTL/tools.h.orig	2009-09-01 16:20:02.000000000 -0300
+++ ntl-5.5.2/include/NTL/tools.h	2009-09-01 16:21:14.000000000 -0300
@@ -10,6 +10,7 @@
 
 #include <cstdlib>
 #include <cmath>
+#include <cstdio>
 #include <iostream>
 
 #else
@@ -251,6 +252,11 @@ long IsEOFChar(long c);
 long CharToIntVal(long c);
 char IntValToChar(long a);
 
+/*
+  This function is not present in vanilla NTL 5.5.2.
+  See tools.c for documentation.
+ */
+void SetErrorCallbackFunction(void (*func)(const char *s, void *context), void *context);
 
 
 void Error(const char *s);
diff -p -up ntl-5.5.2/src/tools.c.orig ntl-5.5.2/src/tools.c
--- ntl-5.5.2/src/tools.c.orig	2009-09-01 16:19:48.000000000 -0300
+++ ntl-5.5.2/src/tools.c	2009-09-01 16:27:23.000000000 -0300
@@ -17,9 +17,37 @@ NTL_START_IMPL
 
 void (*ErrorCallback)() = 0;
 
+/*************** start of sagemath alternate error handling ***************/
+/*
+   The following code differs from vanilla NTL 5.5.2.
+
+   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;
+}
+/**************** end of sagemath alternate error handling ****************/
 
 void Error(const char *s)
 {
+/*************** start of sagemath alternate error handling ***************/
+   if (ErrorCallbackFunction != NULL)
+      ErrorCallbackFunction(s, ErrorCallbackContext);
+/**************** end of sagemath alternate error handling ****************/
+
    cerr << s << "\n";
    _ntl_abort();
 }