#define problem

[Rayn]

Hi All,

I am defining as follows,

#define REIN (a) if(a == NULL) return -1;

when I try to use this thing in my function like ..

void abc(char* aName)
{
REIN(aName);
}

It gives me a compiler error .. Undefined Identifier "a" ..

what can be the problem?

thannks in Advance.

...
KiraN Puranik.

 

[Sumit Rajan]

Hi All,

I am defining as follows,

#define REIN (a) if(a == NULL) return -1;

You probably want to change that to:
#define REIN(a) if(a == NULL) return -1

(Notice the space that I have removed just after "REIN" and before "(a)")

when I try to use this thing in my function like ..

void abc(char* aName)
{
REIN(aName);
}

Now (assuming you have made the change stated above) you have a
completely different issue. You have stated above that abc() is *void*
function. However, when you expand the macro REIN, you get:

void abc(char* aName)
{
if(aName == 0) return -1;
}

You're attempting to return a value from a void function.

Regards,
Sumit.

 

[Sumit Rajan]

You may like to avoid macros as far as possible. See:
http://www.parashift.com/c++-faq-lite/inline-functions.html#faq-9.5

 

[Ian Collins]

Hi All,

I am defining as follows,

#define REIN (a) if(a == NULL) return -1;

Don't. Use an inline function.

 

[Martijn van Buul]

* Ian Collins:

Don't. Use an inline function.

Not that I'm disagreeing with the general sentiment, but using an inline
function wouldn't work here, would it? Or how did you plan to use an inline
function that's capable of aborting the calling function?

OP might want to use

#define REIN(a) do { if (!(a)) return -1; } while(false)

although I wouldn't use it either, as there's little benefit over just
using the if-statement directly.

 

[Ron Natalie]

Don't. Use an inline function.

And just how is an inline function going to do the control construct
he has above?

 

[siddhu]

You can use Inline functions.

But for this case you need to remove space between REIN and (a) in the
macro.
And do not return -1 if your function has void as return value.