Version 5.0 The LEDA User Manual

4.11 Error Handling ( error )
LEDA tests the preconditions of many (not all!) operations. Preconditions are never
tested, if the test takes more than constant time. If the test of a precondition fails an
error handling routine is called. It takes an integer error number i and a char∗ error
message string s as arguments. The default error handler writes s to the diagnostic
output (cerr) and terminates the program abnormally if i ≠ 0. Users can provide their
own error handling function handler by calling
set_error_handler(handler)
After this function call handler is used instead of the default error handler. handler
must be a function of type void handler(int, const char∗). The parameters are replaced
by the error number and the error message respectively.
New:
Starting with version 4.3 LEDA provides an exception error handler
void exception error handler(int num, const char ∗ msg)
This handler uses the C++exception mechanism and throws an exception of type
leda exception instead of terminating the program. An object of type leda exception stores
a pair consisting of an error number and an error message. Operations e.get msg( ) and
e.get num( ) can be called to retrieve the corresponding values from an exception object
e.
1. Operations
#include < LEDA/system/error.h >
void
error handler(int err no, const char ∗ msg)
reports error messages by passing err no and msg
to the default error handler.
LedaErrorHandler set error handler(void (∗err handler)(int, const char∗))
sets the default error handler to function
err handler. Returns a pointer to the previous error
handler.
LedaErrorHandler get error handler( ) returns a pointer to the current default error handler.
void
catch system errors(bool b = true)
after a call to this function system errors ( e.g.
bus errors and segmentation faults) are handled
by LEDA’s error handler.