* Export YAML::detail::node::m_amount
The internal header node/detail/node.h is included by public headers;
YAML::detail::node is implemented in the header itself, and thus it gets
inlined... except for its static m_amount class member, which is
instantiated in the library only. Right now all the symbols of yaml-cpp
are exported (nothing is hidden), so the linker will find node::m_amount
in the yaml-cpp library.
As solution/workaround, explicitly export YAML::detail::node::m_amount.
* CMake: use GenerateExportHeader
Make use of the GenerateExportHeader CMake module to generate the dll.h
header with export macros.
While the produced dll.h is different, the result should be the same,
i.e. nothing changes for yaml-cpp or its users.
* CMake: hide all the symbols by default
Hide all the symbols that are not explicitly exported with YAML_CPP_API.
This way the ABI will be way smaller, and only actually exposing the
public classes/functions.
It seems that it's not necessary to export those members (as long as you can't access them), and most of them are STL instances, which apparently cause lots of problems for DLLs. (For example, you simply can't export instances of std::map; see http://support.microsoft.com/kb/168958.)
