C function with parameter types declared after parameters? [duplicate]

Question

Possible Duplicate:
Declaring function parameters after function name
C function syntax, parameter types declared after parameter list

I'm fairly new to C and was mucking around with timing and came across the following function. I can get it to work by passing pointers to it. I don't really understand whats happening here though. What does the third line do and how is the second line even legal?

int 
timeval_subtract (result, x, y)
     struct timeval *result, *x, *y;
{
  ... (function code here)
}

Mysticial · Accepted Answer · 2011-09-14 04:05:28Z

5

This is very old C syntax for function declaration. It is not recommended to use it.

http://msdn.microsoft.com/en-us/library/efx873ys.aspx

answered Sep 14, 2011 at 4:05

Mysticial

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Mateen Ulhaq · Accepted Answer · 2011-09-14 04:09:45Z

3

Seems like some old C code. (Kernighan & Ritchie, according to the other answers.)

This defines the order of the arguments:

timeval_subtract (result, x, y)

This defines their types:

 struct timeval *result, *x, *y;

It's the same as:

int timeval_subtract (struct timeval *result,
                      struct timeval *x,
                      struct timeval *y)
{
    // ...
}

(Those structs are redundant in C++, and the newest version of C, IIRC.)

answered Sep 14, 2011 at 4:09

Mateen Ulhaq

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K-ballo · Accepted Answer · 2011-09-14 04:05:39Z

0

That looks like pretty ancient C, like K&R C or something... I do not think that's legal ANSI C.

answered Sep 14, 2011 at 4:05

K-ballo

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