CODEWITHSUNDEEP
c++clangc++17
Ryhor Spivak
Ryhor Spivak

Reputation: 263

extern array as non-type template argument with clang c++1z

template<int const * pci> struct X {};
extern int const ai[];
X<ai> xi;
int const ai[] = {0,1,2,3};

If I try to compile this code with "clang++ -std=c++1z" it result in error:

test.cpp:4:3: error: non-type template argument refers to subobject '&ai'

But it isn't subobject.

http://en.cppreference.com/w/cpp/language/template_parameters doesn't list any suitable limitation for extern arrays in '(since C++17)' section for non-type arguments.

Such code works fine with -std=c++14. And GCC also compiles it without errors in c++1z mode: https://godbolt.org/g/K9wZ4g

Is it a clang bug? Or is this code wrong?

Upvotes: 4

Views: 781

Answers (1)

Shuo Chen
Shuo Chen

Reputation: 156

Yes, it's a clang bug, confirmed by clang developer and has been fixed in trunk (r311970). http://lists.llvm.org/pipermail/cfe-dev/2017-August/055249.html

Meanwhile, to work around it, you need to write the length of array in the declaration explicitly.

extern int const ai[4];

Upvotes: 3

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