The contents of the rest of this chapter might be useful only for those who want to create an interface to igraph from another language. Most readers can safely skip to the next chapter.

You can write and install error handlers simply by defining a function of type igraph_error_handler_t and calling igraph_set_error_handler(). This feature is useful for interface writers, as igraph will have the chance to signal errors the appropriate way, eg. the R interface defines an error handler which calls the error() function, as required by R, while the Python interface has an error handler which raises an exception according to the Python way.

If you want to write an error handler, your error handler should call IGRAPH_FINALLY_FREE() to deallocate all temporary memory to prevent memory leaks.

igraph_error_handler_t*
igraph_set_error_handler(igraph_error_handler_t* new_handler);