What causes a SIGSEGV

Wikipedia has the answer, along with a number of other sources.

A segfault basically means you did something bad with pointers. This is probably a segfault:

char *c = NULL;
*c; // dereferencing a NULL pointer

Or this:

char *c = "Hello";
c[10] = 'z'; // out of bounds, or in this case, writing into read-only memory

Or maybe this:

char *c = new char[10];
delete [] c;
c[2] = 'z'; // accessing freed memory

Same basic principle in each case – you’re doing something with memory that isn’t yours.

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