Segfault

[Triumph]

This code compiles fine but when I run it I'm getting a segmentation Fault. I'm not sure why. The program is suppose to Add two numbers without using the + operator.

#include <stdio.h>
#include <stdlib.h>

int add(int a,int b);
 
int main( int argc, char *argv[] ){

  int x;
  int y;

  x = atoi(argv[1]);
  y = atoi(argv[2]);

  printf("The sum of x and y is %d", add(x,y));

  return 0;

}

int add(int a, int b){

  if( a == b) return (a);

  return(add( ++a , --b ) );

}

Any Help would be greatly appreciated.

[BEN10]

the way i see it, when you do this

return(add( ++a , --b ) );

theres no end to this recursive call.for eg when 3 and 2 are to be added, then this recursive call has no end because a is never getting equal to b.

[grumpy]

There is also the slight inconvenience that incrementing is an addition operation (as is decrementing, with somewhat more scope for liberal interpretation).

[vart]

instead of
if( a == b) return (a);

should be

if( 0 == b) return (a);

also it is good idea check that b >=0 before processing

[matsp]

And even if the code works for small numbers, it will NEVER work for large numbers (about half a million or so would be the max, depending a little bit on the processor, OS and optimization levels [unless the compiler figures out that it's tail recursion and optimizes the recursion away completely - which is possible].

--
Mats

[Maz]

Yes. Too deep reqursion will get you in troubles. Hence I would suggest you to think bitwise operations in loop. Basically you can do the summing with AND, XOR and shift to left.

I'll leave the rest for you to ponder