overrun screw

A variety of fandango on core produced by a C program scribbling past the end of an array (C implementations typically have no checks for this error). This is relatively benign and easy to spot if the array is static; if it is auto, the result may be to smash the stack - often resulting in heisenbugs of the most diabolical subtlety. The term "overrun screw" is used especially of scribbles beyond the end of arrays allocated with malloc; this typically overwrites the allocation header for the next block in the arena, producing massive lossage within malloc and often a core dump on the next operation to use stdio or malloc itself.