[cfe-dev] Linkage of static local variables in available_externally definitions

[David Blaikie via cfe-dev]

In implementing modular codegen, specifically verifying the behavior for
static local variables in inline functions in modular headers, I came
across a piece of logic in Clang's linkage calculation that seems off.

To demonstrate a real-world example:

template<typename T>
inline void f() { static int i; }
extern template void f<int>();
...
template void f<int>();

In the TU with the extern template declaration, an available_externally
definition of f<int> and f<int>::i are provided (when optimizations are
enabled).

In the TU with the extern template definition, a weak_odr definition of
f<int> is provided but a linkonce_odr definition of f<int>::i is provided.

This surprises me and doesn't seem correct. What if the TU with the
weak_odr definition is optimized to the point of removing the f<int>::i
definition - but the available_externally TU is not - it inlines f<int> but
leaves a use of f<int>::i available?

What's the deal here - am I missing something that makes this safe/correct?

- Dave
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