CODEWITHSUNDEEP
cerror-handlingreturn-value
hari
hari

Reputation: 9733

what does this C code do with return code?

A function returns TRUE on failure and FALSE on success.

I see some such functions do this towards end of itself:

return return_code != 0;

or

return (return_code != 0);

And in this function, at each error case, it returns TRUE - which is fine and what it should do in case of error.

But what does above code signify? Is it trying to make sure that return_code is FALSE - explicitly?

Upvotes: 3

Views: 232

Answers (4)

pnezis
pnezis

Reputation: 12321

A simple example to make it clear, with a function that divides a with b. Returns true if the division can be evaluated false otherwise

bool div(double a, double b, double& r)
{
   int return_code = 1;
   if (b == 0) // cannot divide
      return_code = 0;
   else
      r = a/b;

   return (return_code != 0);
}

In this simple example only if b==0 the return_code will be 0 so as Marc replied it will return false. In any other case it will return true. Of course there is no reason to do something like this in such a simple function. In more complicated function where the success or not can change in many places, it is a common practice to use such return statements.

Upvotes: 1

dbeer
dbeer

Reputation: 7203

Just a further explanaion -

It is most likely that somewhere in the program TRUE and FALSE are defined:

#define TRUE  1
#define FALSE 0

When a boolean expression is evaluated, the result is always 1 or 0, 1 if the boolean expression evaluates to true, and 0 if it is false. That is why you can test if a boolean expression evaluates to TRUE or FALSE. If you're just curious about boolean expressions and want more basic information, here is a decent tutorial.

Upvotes: 1

Marc B
Marc B

Reputation: 360572

Both depend on the value of return_code:

return_code = 0;

return(return_code != 0); // returns false
return(return_code == 0); // returns true

and

return_code = "anything but a zero";

return(return_code != 0); // returns true
return(return_code == 0); // returns false

Upvotes: 2

K-ballo
K-ballo

Reputation: 81349

I would say is trying to collapse from all the possible integer values to just those of 0 and 1. I'm assuming that the function returns an integral type; evaluating the result as a boolean expression forces the result to just those two values.

Upvotes: 6

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