Thread: return values from a function

Originally Posted by vart

what compiler you are using - I have no problems compiling fixed code in gcc

Code:

struct myvar
{
    int a,b;
};

struct myvar function();

int main(void)
{
    int x,y;

    struct myvar p = function();
    x = p.a;
    y = p.b;

    return x+y;
}

struct myvar function()
{
    struct myvar k;

    k.a = 1;
    k.b = 2;

    return (k);
}

FAQ > main() / void main() / int main() / int main(void) / int main(int argc, char *argv[]) - Cprogramming.com

I am using keil compiler(c51 i think)

Please check with the below

Code:

typedef struct myvar* ptr_myvar;
ptr_myvar function();

Originally Posted by ArunS

Please check with the below

Code:

typedef struct myvar* ptr_myvar;
ptr_myvar function();

hi,

where should i put those statements? tried in couple of places but i get erros

thanks

Originally Posted by laserlight

Are the two values related such that they are rightfully grouped in a struct? If so, then group them in a struct. Returning a struct object as demonstrated by vart in post #2 should work: have you tried to compile the code that vart posted?

As for the "pointer approach", I would expect something like this:

Code:

void function(struct myvar *k)
{
    k->a = 1;
    k->b = 2;
}

Of course, this means that you need to create a struct myvar object in main and pass a pointer to it.

That said, if the two values are not related to each other such that they are rightfully grouped in a struct, then you could consider another approach, e.g., return one of them and have the other be a pointer parameter.


That is a bad idea:

• Changing the return type to be a pointer is likely to be a wrong approach: unless the caller passes in a pointer that is then returned, dynamic memory allocation or some other solution that could be unnecessary complication must be used.
• The pointer typedef could obfuscate the pointer here.

I suggest that you disregard ArunS's suggestion for the reasons I outlined.

hi, thanks

but the problem is likely Keil 51 compiler. so i would be glad if there are other ways around this problem

I have a small screenshot of what i get from the above working code in keil.

it says aggregate initialization needs curly braces and has something to do with language construct that some C compiler won't work with.

Interesting. I tried compiling it with my Keil C51 and got the same error.

Some research indicates that this compiler is intended to largely comply with the old C89/C90 standard.

According to a draft of this standard:

Originally Posted by C89/C90-3.5.7

All the expressions in an initializer for an object that has static storage duration or in an initializer list for an object that has aggregate or union type shall be constant expressions.

So the code you posted is invalid according to that version of the standard, since you're not initializing a struct variable with a constant expression.

This restriction seems limited to initialization and not assignment, so this should work for you:

Code:

struct myvar p;

p = function();

I personally would prefer the pointer approach illustrated above by laserlight.

yes, thanks it worked now.

i am not sure how to use the pointer, haven't tired yet

thanks to all