c++/2645

Wed Apr 25 15:16:00 GMT 2001

The following reply was made to PR c++/2645; it has been noted by GNATS.

From: Paolo Carlini <pcarlini@unitus.it>
To: gcc-gnats@gcc.gnu.org, pcarlini@unitus.it, nobody@gcc.gnu.org
Cc: landauer@apple.com
Subject: Re: c++/2645
Date: Thu, 26 Apr 2001 00:12:02 +0200

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 Sorry for the confusion in the testcase (I badly mistaken a ref to a const int with a const ref

 to an int :(

 (thanks to Doug Landauer for pointing this out!)

 Therefore I cleaned up my testcase (which shows the Gcc problem) as follows:

 ----------------------

 template <typename T>

 struct call_traits

 {

 public:

    typedef T type_less_spec;

 };

 template <typename T>

 struct call_traits<T&>

 {

    typedef T type_more_spec;

 };

 int main()

 {

    int num;

    // Using two typedefs to specify a const & leads to the instant. of the less

    // specialized ("wrong") template

    typedef int& r_type;

    typedef const r_type cr_type;

    call_traits<cr_type>::type_less_spec var1 = num;

    //                    ^^^^^^^^^^^^^^

    // Without the cv-qualifier the more spec. ("right") template is instantiated

    call_traits<r_type>::type_more_spec var4;

    //                   ^^^^^^^^^^^^^^

 }

 ------------------

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2645&database=gcc

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 <pre>Sorry for the confusion in the testcase (I badly mistaken a ref to a const int with a const ref</pre>

 <pre>to an int :(</pre>

 <pre>(thanks to Doug Landauer for pointing this out!)</pre>

 <pre></pre>

 <pre>Therefore I cleaned up my testcase (which shows the Gcc problem) as follows:</pre>

 <pre>----------------------</pre>

 <pre>template <typename T></pre>

 <pre>struct call_traits</pre>

 <pre>{</pre>

 <pre>public:</pre>

 <pre>   typedef T type_less_spec;</pre>

 <pre>};</pre>

 <pre></pre>

 <pre>template <typename T></pre>

 <pre>struct call_traits<T&></pre>

 <pre>{</pre>

 <pre>   typedef T type_more_spec;</pre>

 <pre>};</pre>

 <pre></pre>

 <pre>int main()</pre>

 <pre>{</pre>

 <pre>   int num;</pre>

 <pre></pre>

 <pre>   // Using two typedefs to specify a const & leads to the instant. of the less</pre>

 <pre>   // specialized ("wrong") template</pre>

 <pre>   typedef int& r_type;</pre>

 <pre>   typedef const r_type cr_type;</pre>

 <pre>   call_traits<cr_type>::type_less_spec var1 = num;</pre>

 <pre>   //                    ^^^^^^^^^^^^^^</pre>

 <pre> </pre>

 <pre>   // Without the cv-qualifier the more spec. ("right") template is instantiated</pre>

 <pre>   call_traits<r_type>::type_more_spec var4;</pre>

 <pre>   //                   ^^^^^^^^^^^^^^</pre>

 <pre>}</pre>

 <pre>------------------</pre>

 <pre></pre>

 <pre></pre>

 <pre></pre>

 <pre></pre>

 <pre><A HREF=" http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2645&database=gcc" ;> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2645&database=gcc </A></pre>

 <pre></pre>
 </html>

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