https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99895
Bug ID: 99895
Summary: Function parameters generated wrong in call to member
of non-type template parameter in lambda
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: bisqwit at iki dot fi
Target Milestone: ---
GCC produces false error message:
bug1.cc: In instantiation of ‘consteval void VerifyHash() [with unsigned int
expected_hash = 5; fixed_string<...auto...> ...s = {fixed_string<6>{"khaki"},
fixed_string<6>{"plums"}}]’:
bug1.cc:24:37: required from here
bug1.cc:19:41: error: no matching function for call to
‘fixed_string<6>::data(const fixed_string<6>*)’
19 | [](auto){static_assert(hash(s.data(), s.size()) ==
expected_hash);}(s)
| ~~~~~~^~
bug1.cc:11:27: note: candidate: ‘consteval const char* fixed_string<N>::data()
const [with long unsigned int N = 6]’
11 | consteval const char* data() const { return str; }
| ^~~~
bug1.cc:11:27: note: candidate expects 0 arguments, 1 provided
On this code:
#include <algorithm> // copy_n and size_t
static constexpr unsigned hash(const char* s, std::size_t length)
{
s=s;
return length;
}
template<std::size_t N>
struct fixed_string
{
constexpr fixed_string(const char (&s)[N]) { std::copy_n(s, N, str); }
consteval const char* data() const { return str; }
consteval std::size_t size() const { return N-1; }
char str[N];
};
template<unsigned expected_hash, fixed_string... s>
static consteval void VerifyHash()
{
(
[](auto){static_assert(hash(s.data(), s.size()) == expected_hash);}(s)
,...);
// The compiler mistakenly translates s.data() into s.data(&s)
// and then complains that the call is not valid, because
// the function expects 0 parameters and 1 "was provided".
}
void foo()
{
VerifyHash<5, "khaki", "plums">();
}
Compiler version:
g++-10 (Debian 10.2.1-6) 10.2.1 20210110
