https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79802
Bug ID: 79802
Summary: Conflicting declaration with function pointers/types
Product: gcc
Version: 7.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lutztonineubert at gmail dot com
Target Milestone: ---
Using any g++ with flag -std=c++11 (14 or 17):
```
template<typename T>
struct Foo {
void set(int i) {
}
static constexpr decltype(&Foo<T>::set) i = &Foo<T>::set;
};
template<typename T>
constexpr decltype(&Foo<T>::set) Foo<T>::i;
```
Results in:
> conflicting declaration 'constexpr decltype (& Foo<T>::set(int)) Foo<T>::i'
> note: previous declaration as 'constexpr decltype (& Foo<T>::set(int))
> Foo<T>::i'
The problem exists with c++1(1,4,7) since GCC 4.7. No problem with clang >=
3.2.
A annoying workaround is to use a typedef of the function (compiles fine):
```
template<typename T>
struct Foo {
void set(int i) {
}
typedef decltype(&Foo<T>::set) function_type;
static constexpr function_type i = &Foo<T>::set;
};
template<typename T>
constexpr typename Foo<T>::function_type Foo<T>::i;
```
Maybe similar to:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70943
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57401
Please see also:
http://stackoverflow.com/questions/42534051/conflicting-declaration-for-static-variable-with-template-class
