Re: preprocessor/9764: Varargs macro extension incorrectly expands if the varargs argument is the macro itself

[Ryan Mallon <rpm31@student.canterbury.ac.nz>]

The following reply was made to PR preprocessor/9764; it has been noted by GNATS.

From: Ryan Mallon <rpm31@student.canterbury.ac.nz>
To: neil@gcc.gnu.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Cc:  
Subject: Re: preprocessor/9764: Varargs macro extension incorrectly expands if the varargs argument is the macro itself
Date: Thu, 20 Feb 2003 13:04:50 +1300

 neil@gcc.gnu.org wrote:
 
 >Synopsis: Varargs macro extension incorrectly expands if the varargs argument is the macro itself
 >
 >State-Changed-From-To: open->closed
 >State-Changed-By: neil
 >State-Changed-When: Wed Feb 19 23:48:50 2003
 >State-Changed-Why:
 >    3.1 and later give the following, which is correct.  I've not checked 3.0, but I expect it's similar.
 >    
 >    $ cat /tmp/bar.c
 >    #define func(a, varargs...) _func(a, ##b)
 >
 Opps, I dont know how I missed that. The above line is incorrect, it 
 should read:
 
 #define func(a, varargs...) _func(a, ##varargs)
 
 Which is valid and allows the following uses:
 
 func(a);
 func(a, b);
 func(a, b, c);
 
 Which preprocess correctly to:
 
 _func(a);
 _func(a, b);
 _func(a, b, c);
 
 The problems occurs when the macro name itself is used in the varargs 
 part: e.g
 
 func(a, func(b, c));
 
 Incorrectly expands to:
 
 _func(a, func(b, c));
 
 Without the token paste opperator in the defintion it works as expected, 
 but then I cannot have varargs=0. Im working with a large amount of 
 existing code, so I cannot alter the actual calls on the macro definition.
 
 Sorry for the inconvience,
 Ryan Mallon