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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Bug with const and partial template spepcialization in C++17"
href="https://bugs.llvm.org/show_bug.cgi?id=49684">49684</a>
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<th>Summary</th>
<td>Bug with const and partial template spepcialization in C++17
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>11.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++17
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>eldlistmailingz@tropicsoft.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>The code:
#include <iostream>
#include <cstddef>
#include <type_traits>
template <class T,T (*g)(),bool (*s)(T),class NP = std::nullptr_t,class dummy =
void> struct pfun;
template <class T,T (*g)(),bool (*s)(T)>
struct pfun<T,g,s,std::nullptr_t,typename std::enable_if<g != nullptr &&
(std::is_const<T>::value || s == nullptr)>::type>
{
pfun() {std::cout << "class pfun<T,g,s,std::nullptr_t,typename
std::enable_if<g != nullptr && (std::is_const<T>::value || s ==
nullptr)>::type>\n";}
};
char const gl_r_const_ch('c');
char const gl_fun_r_read_const_ch() { return gl_r_const_ch; }
pfun<char const,&gl_fun_r_read_const_ch,nullptr> pf_read_const_ch;
// char gl_r_ch('c');
// char gl_fun_r_read_ch() { return gl_r_ch; }
// pfun<char,&gl_fun_r_read_ch,nullptr> pf_read_ch;
int main() { return 0; }
Compiled with clang 11.0 the result is:
"test_pmf.cpp:15:50: error: implicit instantiation of undefined template
'pfun<const char, &gl_fun_r_read_const_ch, nullptr, nullptr_t, void>'
pfun<char const,&gl_fun_r_read_const_ch,nullptr> pf_read_const_ch;
^
test_pmf.cpp:5:95: note: template is declared here
template <class T,T (*g)(),bool (*s)(T),class NP = std::nullptr_t,class dummy =
void> struct pfun;"
If you uncomment the three commented lines and comment the three lines above it
( disregarding the space line ), the code compiles with no errors. Furthermore
if you compile in C++14 mode the code as shown there are no errors, and if you
compile with gcc-10.2 in C++14 or C++17 mode there are no errors. Using a 'char
const' rather than just a 'char' should not result in the code not working in
C++17.</pre>
</div>
</p>
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