Output of C Programs | Set 16

Predict the output of below C programs.

Question 1

#include <stdio.h>

char* fun()
{
  return "awake";
}
int main()
{
  printf("%s",fun()+ printf("I see you"));
  getchar();
  return 0;
}

Output: Some string starting with “I see you”
Explanation: (Thanks to Venki for suggesting this solution)
The function fun() returns pointer to char. Apart from printing string “I see you”, printf() function returns number of characters it printed(i.e. 9). The expression [fun()+ printf(“I see you”)] can be boiled down to [“awake” + 9] which is nothing but base address of string literal “awake” displaced by 9 characters. Hence, the expression [“awake” + 9] returns junk data when printed via %s specifier till it finds ‘\0’.

Question 2

#include <stdio.h>

int main()
{
  unsigned i ;
  for( i = 0 ; i < 4 ; ++i )
  {
    fprintf( stdout , "i = %d\n" , ("11213141") ) ;
  }

  getchar();
  return 0 ;
}

Output: Prints different output on different machines.
Explanation: (Thanks to Venki for suggesting this solution)
The format specifier is %d, converts the base address of string “11213141” as an integer. The base address of string depends on memory allocation by the compiler. The for loop prints same address four times. Try to use C++ streams, you will see power of type system.

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