Re: Regression with strn-stuff

[Pedro Alves <pedro_alves at portugalmail dot pt>]

Nick Clifton escreveu:
> Hans-Peter wrote:
>
> > Gotta find a way to automatically check the const-stringness of
> > the second operand.  Use __builtin_constant_p in a checking
> > macro enabled for gcc?
>
> Is there such a function ?  I did not know, but if it does exist then 
> yes, using it would be a good idea.

In my original:
#define const_strcmp(DST, ORG) \
  strncmp (DST, ORG "", sizeof (ORG) - 1)

The double double-quotes ("") were there to check if the parameter
was a compile time const string, since it is legal in C to write a 
string this way:
("string part 1" "string part 2").

I had played with __builtin_constant_p too, but since it was gcc 
specific I dropped it.
Isn't the double quotes version OK?

The double double-quotes ) version only doesn't work when you pass
CONST_STRNEQ a string inside parentheses, like in:

#define MY_STRING ("a string")
CONST_STRNEQ (a_str, MY_STRING);

Since it would expand to:
... ("a string") "" ...
, which doesn't work. But the parenthesis in this cases add no value,
so then can be safely removed.

Cheers,
Pedro Alves