When the diff process spawned by wdiff dies for some reason, wdiff will exit immediately, without unlinking the temporary files containing the input to diff. This affects the test suite in particular, as Santiago Vila reported.

Most other places in the code longjmp to signal_label upon interruption, where the cleaning is performed. But complete_input_program will exit instead. Perhaps the cleaner solution would be replacing all that longjmp stuff with some cleanup function to be registered using atexit. That would take care of all those calls to the error function as well.