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[WIP] bpo-39465: Mark _Py_Identifier.object as atomic #20390

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[WIP] bpo-39465: Mark _Py_Identifier.object as atomic #20390

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[WIP] bpo-39465: Mark _Py_Identifier.object as atomic 
This PR is basically a test to check if C compilers used by CPython
support C11 _Atomic specifier.
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@vstinner
vstinner committed May 25, 2020
commit 5cfdbab1175aec596e16eeafe418eba21e29c768
5 changes: 4 additions & 1 deletion Include/cpython/object.h
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Expand Up @@ -45,7 +45,10 @@ PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
typedef struct _Py_Identifier {
struct _Py_Identifier *next;
const char* string;
PyObject *object;
// bpo-39465: _PyUnicode_FromId() can be called by multiple threads
// running in different interpreters. Use an atomic variable rather
// than a lock for better parallelism.
_Atomic PyObject *object;
} _Py_Identifier;

#define _Py_static_string_init(value) { .next = NULL, .string = value, .object = NULL }
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28 changes: 17 additions & 11 deletions Objects/unicodeobject.c
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Expand Up @@ -2275,18 +2275,24 @@ PyUnicode_FromString(const char *u)
PyObject *
_PyUnicode_FromId(_Py_Identifier *id)
{
if (!id->object) {
id->object = PyUnicode_DecodeUTF8Stateful(id->string,
strlen(id->string),
NULL, NULL);
if (!id->object)
return NULL;
PyUnicode_InternInPlace(&id->object);
assert(!id->next);
id->next = static_strings;
static_strings = id;
if (id->object) {
return (PyObject *)id->object;
}
return id->object;

PyObject *object;
object = PyUnicode_DecodeUTF8Stateful(id->string,
strlen(id->string),
NULL, NULL);
if (!object) {
return NULL;
}

PyUnicode_InternInPlace(&object);
id->object = (_Atomic PyObject *)object;
assert(!id->next);
id->next = static_strings;
static_strings = id;
return object;
}

static void
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