g++4.8

The following program on running with g++ 4.8.2 gave the output 12 on a 32-bit Linux system: vector<char> v; cout << sizeof(v) << endl; I saw this and know that sizeof(v) could be implementation specific. Still, I was wondering what might be causing that vector to have a size of 12. What I think is that the iterators v.begin() and v.end() might be contributing to 8 bytes of the size. Am I correct? If yes, what is contributing to the remaining 4 bytes of size? If not, what are these 12 bytes all about? Take a look at the sources. libstdc++ is part of the gcc download. Anyway, the container must

I have the following enum specification: enum class FaceDirection : int8 { Down, Up }; g++ 4.8.1 gives the following error: warning: elaborated-type-specifier for a scoped enum must not use the ‘class’ keyword What causes this? Check the type you are deriving the enum class from exists. In this case, there was no typedef specified for int8 . 来源： https://stackoverflow.com/questions/20459120/elaborated-type-specifier-for-a-scoped-enum-must-not-use-the-class-keyword

The following code: int main() { int a, b, c, d, e, f, g; auto func = [&](){cout << a << b << c << d << e << f << g << endl;}; cout << sizeof(func) << endl; return 0; } outputs 56 compiled with g++ 4.8.2 Since all local variables are stored in the same stack frame, remembering one pointer is sufficient to locate the addresses of all local variables. Why the lambda expression constructs a so big unnamed function object? I do not understand why you seem surprised. The C++ Standard gives a set of requirements, and every single implementation is free to pick any strategy that meets the

Should the type trait be able to handle cases such as std::vector < std::unique_ptr <int> > and detect that it's not copy constructible? Here's an example at https://ideone.com/gbcRUa (running g++ 4.8.1) #include <type_traits> #include <vector> #include <iostream> #include <memory> int main() { // This prints 1, implying that it's copy constructible, when it's clearly not std::cout << std::is_copy_constructible< std::vector<std::unique_ptr<int> > >::value << std::endl; return 0; } If this is the correct behavior for is_copy_constructible , is there a way to detect that the copy construction is