Thread-local storage support across dynamic-library boundaries.
Normally, a std::thread::LocalKey refers to a specific memory location in a
single binary. This library adds support for thread-local storage across
binaries by storing thread-local values in a shared map between a host and one
or more plugins.
Use the host feature to enable the host capabilities (in exactly one binary to
be loaded in memory), and use the plugin feature to enable plugin capabilities
(in zero or more binaries to be loaded).
In each binary (both host and plugins), call Context::initialize with the
host context prior to any thread-local storage being accessed (typically as part
of the binary startup routine).
Besides that, the thread_local! macro works exactly like std::thread_local!
for both the host and plugins. Note that thead-local values are indexed by the
given name, type, and module path, so these must not conflict. Also note that
stored values must be abi-stable. Abi-stability is not enforced in LocalKey
with the abi_stable::StableAbi trait for library flexibility, but use of
abi_stable is highly encouraged.
Note that both host and plugin may be enabled together, specifically for use
in workspaces that may contain both the host and plugin(s).