Passing pointer to extern(C++) templated function

[kinke]

On Tuesday, 13 October 2020 at 09:23:48 UTC, Jamie wrote:
> It appears that func3 and func4 take on different types 
> depending on other variables being present? Is this expected?

Nope, it's a bug in the Itanium C++ mangler, please file a bug. 
MSVC++ mangling seems fine, after fixing the D declarations to

void func3(T)(T* b, const(T)* a);
void func4(T)(const(T)* a, T* b);

[A D `const T*` is equivalent to C++ `const T* const`; this 
matters for MSVC mangling...].