Why does this code work in Clang++ but not G++?
c++, c++11, clang++, g++
Solution
C++11 8.5.1 [dcl.init.aggr] p1 defines aggregate types:
An aggregate is an array or a class (Clause 9) with no user-provided constructors (12.1), no brace-or-equal-initializers for non-static data members (9.2), no private or protected non-static data members (Clause 11), no base classes (Clause 10), and no virtual functions (10.3).
user-provided is defined in 8.4.2 [dcl.fct.def.default] p4:
... A special member function is user-provided if it is user-declared and not explicitly defaulted or deleted on its first declaration.
`Foo` has two user-declared constructors, both of which are explicitly defaulted or deleted on their first declaration, so `Foo` is an aggregate.
GCC is wrong.
EDIT: This is in fact GCC bug 52707.
Problem
Consider the following code: ``` struct Foo { int x, y; Foo() = default; Foo(const Foo&) = delete; Foo& operator=(const Foo&) = delete; }; int main() { Foo f1 {1, 2}; Foo f2 = {1, 2}; } ``` Compiling with clang++ yields no errors: ``` $ clang++ --version Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn) Target: x86_64-apple-darwin12.4.0 Thread model: posix $ clang++ -std=c++11 -stdlib=libc++ -pedantic t.cpp -o out ...builds and runs fine... ``` However, compiling with g++ 4.8.1 through ideone gives errors: ``` prog.cpp: In function ‘int main()’: prog.cpp:12:17: error: no matching function for call to ‘Foo::Foo(<brace-enclosed initializer list>)’ Foo f1 {1, 2}; ^ prog.cpp:12:17: note: candidate is: prog.cpp:5:5: note: Foo::Foo() Foo() = default; ^ prog.cpp:5:5: note: candidate expects 0 arguments, 2 provided prog.cpp:13:19: error: could not convert ‘{1, 2}’ from ‘<brace-enclosed initializer list>’ to ‘Foo’ Foo f2 = {1, 2}; ^ ``` If I remove `Foo(const Foo&) = delete;` then it compiles fine in g++4.8.1. Is there an error in my code that one compiler is ignoring but the other is not?