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To: gcc-help@gcc.gnu.org
From:  Larry Evans <cppljevans@suddenlink.net>
Subject:  Re: Help with Code Validation of Variadic templates
Date: Mon, 17 Aug 2009 03:18:00 -0000
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On 12/07/07 15:12, Rene Buergel wrote:
> I'm currently playing around using mainline with the variadic template 
> feature and would like to hear some comments on code gcc is rejecting.
> 
> #1:
> =====
> 1 template<typename T, T a, T... Args> T max()
> 2 {
> 3     return a > max<T, Args>() ? a : max<T, Args>();
> 4 };
> 5
> 6 template<typename T, T a, T b>T max()
> 7 {
> 8     return a > b ? a : b;
> 9 };
> 
> int main()
> {
>    unsigned int a = max<unsigned int, 3, 2>();
>    unsigned int a = max<unsigned int, 3, 2, 5>();
> }
> 
> =====
> Using the non-variadic template, everything works fine. With the 
> variadic templates, gcc issues an error in line 3:
> error: parameter packs not expanded with `...':
> note:         'Args'
[snip]
I think this is an instance of bug 40092:

   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40092

A 1 line patch to gcc/cp/tree.c has been proposed there.
You might try the patch an see if it solves your problem.

-regards,
Larry