https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86233
Bug ID: 86233
Summary: A tricky code sample
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zhonghao at pku dot org.cn
Target Milestone: ---
he code is as follow:
#define _GLIBCXX_DEBUG
#include <vector>
struct T { int i; };
int swap_calls;
namespace std
{
template<>
void
vector<T, allocator<T> >::swap(vector<T, allocator<T> >&)
{ ++swap_calls; }
}
// Should use vector specialization for swap.
int main()
{
std::vector<T> A;
std::vector<T> B;
swap_calls = 0;
std::swap(A, B);
return swap_calls;
}
It comes from a gcc bug report:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021
I tried the latest g++, and it accepts the above code, but clang++ rejects it.
The error message is as follow:
code0.c.cpp:12:28: error: 'swap' is missing exception specification
'noexcept(noexcept(declval<std::__debug::vector<T, std::allocator<T> >::_Base
&>().swap(__x)))'
vector<T, allocator<T> >::swap(vector<T, allocator<T> >&)
^
noexcept(noexcept(declval<std::__debug::vector<T, std::allocator<T> >::_Base
&>().swap(__x)))
/usr/local/bin/../lib/gcc/x86_64-pc-linux-gnu/8.0.1/../../../../include/c++/8.0.1/debug/vector:688:7:
note: previous declaration is here
swap(vector& __x)
^
1 error generated.
I reported the difference as a bug to clang:
https://bugs.llvm.org/show_bug.cgi?id=37852
Richard Smith believe that clang++ is correct. So, shall g++ reject the code?
