pointers - Why does this C struct code work? -

i toying pointers structures , array of structures see how work. confounded why following piece of work compiles , produces right result:

#include <stdio.h> #include <stdlib.h> int main() {     typedef struct {         char *name;         int count;     } word; word *word_array; word_array = malloc(sizeof(word)); word_array[2048].name = "foo"; word_array[2048].count = 5; printf("%s %d\n", word_array[2048].name, word_array[2048].count); 

this prints: foo 5

how memory malloc allocate word_array? what's going on? undefined behaviour happens compile , run?

how memory malloc allocate word_array?

sizeof(word) bytes, told - enough memory hold 1 word.

what's going on? undefined behaviour happens compile , run?

yes. note it's not surprising compiles (most undefined behaviour not cause compilation error, or warning).

since seem know undefined behaviour, know might crash, or might seem work, or in-between. maybe next tuesday program crash when try show ceo. maybe you'll upgrade compiler in 6 months , it'll start crashing consistently. if program writes files, then maybe it's corrupting files. , on.