https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66921
Billy Donahue <billydonahue at google dot com> changed:
What |Removed |Added
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CC| |billydonahue at google dot com
--- Comment #2 from Billy Donahue <billydonahue at google dot com> ---
(In reply to Vlad Petric from comment #0)
> Created attachment 36010 [details]
> straightforward file (include-less) that fails to compile
>
> template<typename T>
> struct Holder {
> constexpr static const int array[] = { 1, 2, 3 };
> enum {F = array[0]};
> };
>
> class HI: public Holder<int> {};
>
> gcc 4.9.3/Centos linux.
>
> $ g++ -std=c++11 ./x.cc -o x.o -c
> ./x.cc: In instantiation of ‘constexpr const int Holder<int>::array []’:
> ./x.cc:4:18: required from ‘struct Holder<int>’
> ./x.cc:7:18: required from here
> ./x.cc:3:30: error: initializer fails to determine size of
> ‘Holder<int>::array’
> constexpr static const int array[] = { 1, 2, 3 };
> ^
> ./x.cc:3:30: error: array must be initialized with a brace-enclosed
> initializer
> ./x.cc: In instantiation of ‘struct Holder<int>’:
> ./x.cc:7:18: required from here
> ./x.cc:4:8: error: enumerator value for ‘F’ is not an integer constant
> enum {F = array[0]};
>
>
>
> * with gcc 4.8.3, it compiles just fine.
>
> * if I remove the template, it also compiles just fine:
>
> struct Holder {
> constexpr static const int array[] = { 1, 2, 3 };
> enum {F = array[0]};
> };
>
> class HI: public Holder {};
I little bit of trial-and-error on gcc.godbolt.org confirms this is a problem
in gcc in the v4.9 series and beyond to the current v5.2, not a problem in the
v4.8 series.
http://goo.gl/li99SI
Clang compiles it okay, FWIW.
If I explicitly size the array[3], then all gcc's will compile it fine.
template<typename T>
struct Holder {
// builds in modern gcc as long as the 3 is specified.
constexpr static int array[3] = { 123, 234, 345 };
enum {F = array[0]};
};
Holder<void> inst{};
