Question
I get errors when compiling this simple code and if I remove the noexcept I don't get the error:
https://stackoverflow.com/questions/18949457
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Russian#include<vector>
#include<string>
class Foo
{
public:
protected:
Foo(Foo&&) noexcept = default;
Foo& operator=(Foo&&) noexcept = default;
Foo()
{
}
private:
std::vector<std::string> vectorFoo_;
};
This is the errors I get, I understand it is in the instantiation of the exception specification, but I doubt the std::string is not nothrow move constructible,.. the first error make me think there is a bug.
In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: /usr/local/bin/../lib/c++/v1/vector:575:67: error: no member named 'value' in 'std::__1::is_nothrow_move_constructible, std::__1::allocator > > >' NOEXCEPT(is_nothrow_move_constructible::value); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:264: /usr/local/bin/../lib/c++/v1/__config:325:34: note: expanded from macro 'NOEXCEPT' define NOEXCEPT(x) noexcept(x) ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29: note: in instantiation of exception specification for 'vector' requested here std::vector vectorFoo_; ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:265: In file included from /usr/local/bin/../lib/c++/v1/__bit_reference:15: In file included from /usr/local/bin/../lib/c++/v1/algorithm:624: /usr/local/bin/../lib/c++/v1/type_traits:2676:53: note: in instantiation of template class 'std::__1::add_rvalue_reference, std::__1::allocator > > >' requested here : public is_nothrow_constructible<_Tp, typename add_rvalue_reference<Tp>::type> ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: /usr/local/bin/../lib/c++/v1/vector:575:20: note: in instantiation of template class 'std::_1::is_nothrow_move_constructible, std::__1::allocator > > >' requested here NOEXCEPT(is_nothrow_move_constructible::value); ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:264: /usr/local/bin/../lib/c++/v1/__config:325:34: note: expanded from macro 'NOEXCEPT' define NOEXCEPT(x) noexcept(x) ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29: note: in instantiation of exception specification for 'vector' requested here std::vector vectorFoo_; ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: /usr/local/bin/../lib/c++/v1/vector:582:58: error: no member named 'value' in 'std::__1::is_nothrow_move_assignable, std::__1::allocator > > >' is_nothrow_move_assignable::value); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:264: /usr/local/bin/../lib/c++/v1/__config:325:34: note: expanded from macro 'NOEXCEPT' define NOEXCEPT(x) noexcept(x) ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29: note: in instantiation of exception specification for 'operator=' requested here std::vector vectorFoo_; ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:265: In file included from /usr/local/bin/../lib/c++/v1/__bit_reference:15: In file included from /usr/local/bin/../lib/c++/v1/algorithm:624: /usr/local/bin/../lib/c++/v1/type_traits:2760:45: note: in instantiation of template class 'std::__1::add_lvalue_reference, std::__1::allocator > > >' requested here : public is_nothrow_assignableTp>::type, ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: /usr/local/bin/../lib/c++/v1/vector:582:14: note: in instantiation of template class 'std::_1::is_nothrow_move_assignable, std::__1::allocator > > >' requested here is_nothrow_move_assignable::value); ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:264: /usr/local/bin/../lib/c++/v1/__config:325:34: note: expanded from macro 'NOEXCEPT' define NOEXCEPT(x) noexcept(x) ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29: note: in instantiation of exception specification for 'operator=' requested here std::vector vectorFoo_; ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:265: In file included from /usr/local/bin/../lib/c++/v1/__bit_reference:15: In file included from /usr/local/bin/../lib/c++/v1/algorithm:624: /usr/local/bin/../lib/c++/v1/type_traits:2676:53: note: in instantiation of template class 'std::__1::add_rvalue_reference, std::__1::allocator > > >' requested here : public is_nothrow_constructible<_Tp, typename add_rvalue_reference<Tp>::type> ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: /usr/local/bin/../lib/c++/v1/vector:575:20: note: in instantiation of template class 'std::_1::is_nothrow_move_constructible, std::__1::allocator > > >' requested here NOEXCEPT(is_nothrow_move_constructible::value); ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4: In file included from /usr/local/bin/../lib/c++/v1/vector:264: /usr/local/bin/../lib/c++/v1/__config:325:34: note: expanded from macro 'NOEXCEPT' define NOEXCEPT(x) noexcept(x) ^ In file included from /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1: /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29: note: in instantiation of exception specification for 'vector' requested here std::vector vectorFoo_;
My compiler is clang from the top of tree. What am-I doing wrong?
Thanks
Update The error on Coliru. It seam that if I don't specify libc++ and instead use stdlibc++ it compiles. It is starting to look alot like a bug in libc++.
Solution
The code is fine. (and, interestingly enough, so is libc++)
This turns out to be a bug in clang; in fact, recent versions of clang crash when attempting to compile this code.
A patch fixing this in clang is currently being tested and will be part of the 3.4 release. If you can't wait that long, then you should be able to get a fixed version of clang "really soon now" if you are willing to build it from source.
Thanks to Alp from Nuanti for tracking down the clang bug.
OTHER TIPS
My first assumption was, this might be because the move-assignment operator for std::string isn't noexcept (need to check see below).
At least, clang and gcc seem to like this better:
Bar& operator = (Bar&&)
noexcept(
noexcept(std::declval<std::string>() = std::string())
) = default;
Now, on Foo clang and gcc don't quite agree, but here's Clang live on coliru
More food for thought: The standard appears to explicitely specify the assignment operator (as well as move constructor) for std::string as noexcept: § 21.4.2
