Consider the following code:<\/p>\n
\r\n#include \r\n#include \r\nusing namespace std;\r\n\r\n\/\/ base template\r\ntemplate \r\nstruct what_type\r\n{\r\n void operator()()\r\n {\r\n cout << \"T\" << endl;\r\n }\r\n};\r\n\r\n\/\/ specialization 1\r\ntemplate \r\nstruct what_type\r\n{\r\n void operator()()\r\n {\r\n cout << \"T[\" << N << \"]\" << endl;\r\n }\r\n};\r\n\r\n\/\/ specialization 2\r\ntemplate <>\r\nstruct what_type\r\n{\r\n void operator()()\r\n {\r\n cout << \"int[0]\" << endl;\r\n }\r\n};\r\n\r\nint main(void)\r\n{\r\n int x[] = {};\r\n what_type>()();\r\n\r\n return 0;\r\n}\r\n<\/pre>\nI compile this with GCC (g++ (Ubuntu 4.9.1-16ubuntu6) 4.9.1) and I get:<\/p>\n
\r\nbdeane@epsilon:~\/dev\/scratch$ g++ -std=c++1y main.cpp \r\nbdeane@epsilon:~\/dev\/scratch$ .\/a.out\r\nT\r\n<\/pre>\nWhen I use clang (Ubuntu clang version 3.5.0-4ubuntu2 (tags\/RELEASE_350\/final) (based on LLVM 3.5.0)) I get:<\/p>\n
\r\nbdeane@epsilon:~\/dev\/scratch$ clang++ -std=c++1y main.cpp \r\nbdeane@epsilon:~\/dev\/scratch$ .\/a.out\r\nint[0]\r\n<\/pre>\nIt seems GCC is wrong here: I would expect specialization 2 to be selected. Now, if I remove specialization 2, clang gives the same output as GCC (i.e. T<\/code>).<\/p>\nIf I put an assert in the base template member function, both clang and gcc think that T = int[0]<\/code> and give almost identical messages:<\/p>\na.out: main.cpp:53: void what_type<int [0]>::operator()() [T = int [0]]: Assertion `false' failed.<\/code><\/p>\nSo why isn’t specialization 1 selected? (And it makes no difference either if I have a specialization for T[]<\/code> as well as\/instead of T[N]<\/code>.)<\/p>\n