Following up on issue 25658, it was found that the current definition of Py_tss_NEEDS_INIT restricts its use to initialisers in C and cannot be used for arbitrary assignments. It is currently declared as follows:

    #define Py_tss_NEEDS_INIT   {0}

which results in a C compiler error for assignments like "x = Py_tss_NEEDS_INIT".

I proposed to change this to

    #define Py_tss_NEEDS_INIT   ((Py_tss_t) {0})

in compliance with GCC and C99, but that fails to compile in MSVC and probably other old C++-ish compilers.

I'm not sure how to improve this declaration, but given that it's a public header file, restricting its applicability seems really unfortunate.