| Summary: | Conflicting declaration with function pointers/types | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Toni Neubert <lutztonineubert> |
| Component: | c++ | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | daniel.kruegler, webrown.cpp |
| Priority: | P3 | Keywords: | rejects-valid |
| Version: | 7.0.1 | ||
| Target Milestone: | 8.0 | ||
| Host: | Target: | ||
| Build: | Known to work: | 8.0 | |
| Known to fail: | Last reconfirmed: | 2018-02-27 00:00:00 | |
Confirmed, but this seems to have been fixed on trunk by r251438 Fixed in GCC 8+. |
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