what does this statement mean

[raghu]

Hello
This is raghu. And I want to know about the meaning of the statement
given below
log_txt( __FILE__, __LINE__, ##argList);
in above statement what does FILE ,LINE ##argList mean. I want to know
about is it possiable to send arguments like that.
Thanking you in advance

 

[Ian Collins]

Hello
This is raghu. And I want to know about the meaning of the statement
given below
log_txt( __FILE__, __LINE__, ##argList);
in above statement what does FILE ,LINE ##argList mean. I want to know
about is it possiable to send arguments like that.

Look __FILE__, __LINE__ and ## up in K&R. It's all explained clearly there.

 

[Racaille]

Look __FILE__, __LINE__ and ## up in K&R. It's all explained clearly there.

maybe I'm talking out of my ass, but I always thought that using ', ##'
(to suppress the
comma when the last argument is void) is a GCC extension, and not K&R
or standard C.

 

[Richard Heathfield]

Racaille said:

maybe I'm talking out of my ass, but I always thought that using ', ##'
(to suppress the
comma when the last argument is void) is a GCC extension, and not K&R
or standard C.

## is standard C preprocessor syntax for token-pasting. Its use outside a
macro definition (or of course a comment, string literal, etc) is simply an
error.

 

[Random832]

Racaille said:


## is standard C preprocessor syntax for token-pasting. Its use outside a
macro definition (or of course a comment, string literal, etc) is simply an
error.

GCC does assign it special meaning within variadic macro definitions
where the token before it is the comma and the token after it is the
name of the variadic argument list (gcc variadic macros can have that be
somthing other than __VA_LIST__)

This is all off-topic, of course, but still better than trying to
explain it in a "standard" context when it's clearly a non-standard
usage.

 

[Racaille]

## is standard C preprocessor syntax for token-pasting. Its use outside a
macro definition (or of course a comment, string literal, etc) is simply an
error.

OK, is this usage of '##' standard c99 ?

--
#define COCO(a, ...) a, ## __VA_ARGS__
int
main(void)
{
return COCO(0);
}

 

[Richard Bos]

OK, is this usage of '##' standard c99 ?

#define COCO(a, ...) a, ## __VA_ARGS__

No. It's Ganuck.

Richard