Function argument conversions

When a function is called, if a function declaration is present and includes declared argument types, the compiler performs type checking. The compiler compares the data types provided by the calling function with the data types that the called function expects and performs necessary type conversions. For example, when function funct is called, argument f is converted to a double, and argument c is converted to an int:

char * funct (double d, int i);

int main(void){
   float f;
   char c;
   funct(f, c) /* f is converted to a double, c is converted to an int */
   return 0;
}

If no function declaration is visible when a function is called, or when an expression appears as an argument in the variable part of a prototype argument list, the compiler performs default argument promotions or converts the value of the expression before passing any arguments to the function. The automatic conversions consist of the following:

• The integral and floating-point promotions are performed.
• Arrays or functions are converted to pointers.