c - Overwriting of stack static array when the other static array overflows -

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#include<stdio.h>  int main(){   char a[10];   char b[10];   sprintf(a,"hello");   sprintf(b,"aaaaaaaaaabbbbbbbbbbcccccccccc");   printf("%s:%s\n",a,b);   return(0); }  (gdb) p &a $1 = (char (*)[10]) 0x7fffffffe450 (gdb) p &b $2 = (char (*)[10]) 0x7fffffffe440 (gdb) step 2: b = "aaaaaaaaaa" 1: = "bbbbcccccc" printf o/p- bbbbcccccccccc:aaaaaaaaaabbbbbbbbbbcccccccccc

questions-

a comes first in stack frame , b comes later. if b overwriting "bbbbbbbbbb" should go why starting "bbbbcccccccccc"?

also want know if overwrite bp, program terminate?

sure b comes "after" a in stack, stack (often, , assumedly on platform based on print-outs) growns downwards. notice address of b less of a.

so overwrite of b goes a.

also think gdb being clever , printing 10 characters b, since prints 10 a's , there's no termination.

you can't overwrite processor register using rogue string formatting, registers not in memory (in general, , not on x86 might using).

note code invokes undefined behavior, terminate reason.


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