Promote the new opaque PEP-539 type "Py_tss_t" to a known Cython type to avoid...

Promote the new opaque PEP-539 type "Py_tss_t" to a known Cython type to avoid static variable initialisation issues with the "Py_tss_NEEDS_INIT" struct initialiser value.

CHANGES.rst

@@ -27,6 +27,10 @@ Features added
 * The new TSS C-API in CPython 3.7 is supported and has been backported.
   Patch by Naotoshi Seo.  (Github issue #1932)
 
+* Cython knows the new ``Py_tss_t`` type defined in PEP-539 and automatically
+  initialises variables declared with that type to ``Py_tss_NEEDS_INIT``,
+  a value which cannot be used outside of static assignments.
+
 * The set methods ``.remove()`` and ``.discard()`` are optimised.
   Patch by Antoine Pitrou.  (Github issue #2042)
 

Cython/Compiler/Parsing.py

@@ -2710,6 +2710,7 @@ special_basic_c_types = cython.declare(dict, {
     "ssize_t"    : (2, 0),
     "size_t"     : (0, 0),
     "ptrdiff_t"  : (2, 0),
+    "Py_tss_t"   : (1, 0),
 })
 
 sign_and_longness_words = cython.declare(

Cython/Compiler/PyrexTypes.py

@@ -192,7 +192,8 @@ class PyrexType(BaseType):
     #  is_pythran_expr       boolean     Is Pythran expr
     #  is_numpy_buffer       boolean     Is Numpy array buffer
     #  has_attributes        boolean     Has C dot-selectable attributes
-    #  default_value         string      Initial value
+    #  default_value         string      Initial value that can be assigned before first user assignment.
+    #  declaration_value     string      The value statically assigned on declaration (if any).
     #  entry                 Entry       The Entry for this type
     #
     #  declaration_code(entity_code,
@@ -254,6 +255,7 @@ class PyrexType(BaseType):
     is_numpy_buffer = 0
     has_attributes = 0
     default_value = ""
+    declaration_value = ""
 
     def resolve(self):
         # If a typedef, returns the base type.
@@ -1083,6 +1085,7 @@ class PyObjectType(PyrexType):
     name = "object"
     is_pyobject = 1
     default_value = "0"
+    declaration_value = "0"
     buffer_defaults = None
     is_extern = False
     is_subclassed = False
@@ -2226,6 +2229,25 @@ complex_ops = {
 }
 
 
+class CPyTSSTType(CType):
+    #
+    #   PEP-539 "Py_tss_t" type
+    #
+
+    declaration_value = "Py_tss_NEEDS_INIT"
+
+    def __repr__(self):
+        return "<Py_tss_t>"
+
+    def declaration_code(self, entity_code,
+                         for_display=0, dll_linkage=None, pyrex=0):
+        if pyrex or for_display:
+            base_code = "Py_tss_t"
+        else:
+            base_code = public_decl("Py_tss_t", dll_linkage)
+        return self.base_declaration_code(base_code, entity_code)
+
+
 class CPointerBaseType(CType):
     # common base type for pointer/array types
     #
@@ -4088,6 +4110,9 @@ c_gilstate_type = CEnumType("PyGILState_STATE", "PyGILState_STATE", True)
 c_threadstate_type = CStructOrUnionType("PyThreadState", "struct", None, 1, "PyThreadState")
 c_threadstate_ptr_type = CPtrType(c_threadstate_type)
 
+# PEP-539 "Py_tss_t" type
+c_pytss_t_type = CPyTSSTType()
+
 # the Py_buffer type is defined in Builtin.py
 c_py_buffer_type = CStructOrUnionType("Py_buffer", "struct", None, 1, "Py_buffer")
 c_py_buffer_ptr_type = CPtrType(c_py_buffer_type)
@@ -4153,6 +4178,7 @@ modifiers_and_name_to_type = {
 
     #
     (1,  0, "void"): c_void_type,
+    (1,  0, "Py_tss_t"): c_pytss_t_type,
 
     (1,  0, "bint"):       c_bint_type,
     (0,  0, "Py_UNICODE"): c_py_unicode_type,

Cython/Compiler/Symtab.py

@@ -1378,8 +1378,8 @@ class ModuleScope(Scope):
                                   api=api, in_pxd=in_pxd, is_cdef=is_cdef)
         if is_cdef:
             entry.is_cglobal = 1
-            if entry.type.is_pyobject:
-                entry.init = "0"
+            if entry.type.declaration_value:
+                entry.init = entry.type.declaration_value
             self.var_entries.append(entry)
         else:
             entry.is_pyglobal = 1
@@ -1710,8 +1710,8 @@ class LocalScope(Scope):
         entry = Scope.declare_var(self, name, type, pos,
                                   cname=cname, visibility=visibility,
                                   api=api, in_pxd=in_pxd, is_cdef=is_cdef)
-        if type.is_pyobject:
-            entry.init = "0"
+        if entry.type.declaration_value:
+            entry.init = entry.type.declaration_value
         entry.is_local = 1
 
         entry.in_with_gil_block = self._in_with_gil_block

Cython/Includes/cpython/pythread.pxd

@@ -39,10 +39,9 @@ cdef extern from "pythread.h":
     # Cleanup after a fork
     void PyThread_ReInitTLS()
 
-    # Thread Specific Storage (TSS) API in CPython 3.7+
-    ctypedef struct Py_tss_t:
-        pass
-    Py_tss_t Py_tss_NEEDS_INIT
+    # Thread Specific Storage (TSS) API in CPython 3.7+ (also backported)
+    #ctypedef struct Py_tss_t: pass   # Cython built-in type
+    Py_tss_t Py_tss_NEEDS_INIT        # Not normally useful: Cython auto-initialises declared "Py_tss_t" variables.
     Py_tss_t * PyThread_tss_alloc()
     void PyThread_tss_free(Py_tss_t *key)
     int PyThread_tss_is_created(Py_tss_t *key)

Cython/Shadow.py

@@ -385,7 +385,7 @@ py_complex = typedef(complex, "double complex")
 int_types = ['char', 'short', 'Py_UNICODE', 'int', 'Py_UCS4', 'long', 'longlong', 'Py_ssize_t', 'size_t']
 float_types = ['longdouble', 'double', 'float']
 complex_types = ['longdoublecomplex', 'doublecomplex', 'floatcomplex', 'complex']
-other_types = ['bint', 'void']
+other_types = ['bint', 'void', 'Py_tss_t']
 
 to_repr = {
     'longlong': 'long long',
@@ -420,13 +420,13 @@ for name in complex_types:
     gs[name] = typedef(py_complex, to_repr(name, name))
 
 bint = typedef(bool, "bint")
-void = typedef(int, "void")
+void = typedef(None, "void")
+Py_tss_t = typedef(None, "Py_tss_t")
 
 for t in int_types + float_types + complex_types + other_types:
     for i in range(1, 4):
         gs["%s_%s" % ('p'*i, t)] = gs[t]._pointer(i)
 
-void = typedef(None, "void")
 NULL = gs['p_void'](0)
 
 # looks like 'gs' has some users out there by now...

tests/run/tss.pyx

@@ -3,16 +3,21 @@
 from cpython.pythread cimport *
 
 
+cdef Py_tss_t *pass_py_tss_t_ptr(Py_tss_t *value):
+    return value
+
+
 def tss_create_delete():
     """
     >>> tss_create_delete()
     (True, False)
     """
-    cdef Py_tss_t tss_key = Py_tss_NEEDS_INIT
+    cdef Py_tss_t tss_key
     cdef bint after_create, after_delete
     if PyThread_tss_create(&tss_key) != 0:
         raise MemoryError()
     after_create = PyThread_tss_is_created(&tss_key) != 0
+    assert after_create == PyThread_tss_is_created(pass_py_tss_t_ptr(&tss_key))
     PyThread_tss_delete(&tss_key)
     after_delete = PyThread_tss_is_created(&tss_key) != 0
     return (after_create, after_delete)
@@ -58,7 +63,7 @@ def tss_set_get():
     >>> tss_set_get()
     1
     """
-    cdef Py_tss_t tss_key = Py_tss_NEEDS_INIT
+    cdef Py_tss_t tss_key
     cdef int the_value = 1
     cdef int ret_value
     if PyThread_tss_create(&tss_key) != 0: