This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
According to 9.11 [dcl.link] paragraph 7,
A declaration directly contained in a linkage-specification is treated as if it contains the extern specifier (9.2.2 [dcl.stc]) for the purpose of determining the linkage of the declared name and whether it is a definition. Such a declaration shall not specify a storage class.
This prohibits a declaration like
extern "C++" thread_local int n;
Should this be changed?
Rationale (June, 2014):
This restriction is the same for static and simply requires that the braced form of linkage-specification be used.