python · vstinner · Oct 14, 2021
diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
@@ -572,6 +572,17 @@ Porting to Python 3.11
   header provides functions like ``printf()`` and ``fopen()``.
   (Contributed by Victor Stinner in :issue:`45434`.)
 
+* Convert the following macros to static inline functions to disallow using
+  them as l-value:
+
+  * :c:func:`PyByteArray_AS_STRING`
+  * :c:func:`PyBytes_AS_STRING`
+  * :c:func:`PyFloat_AS_DOUBLE`
+
+  Moreover, :c:func:`PyUnicode_AS_UNICODE` becomes an alias to
+  :c:func:`PyUnicode_AsUnicode`.
+  (Contributed by Victor Stinner in :issue:`45476`.)
+
 Deprecated
 ----------
 

diff --git a/Include/cpython/bytearrayobject.h b/Include/cpython/bytearrayobject.h
@@ -11,10 +11,19 @@ typedef struct {
     Py_ssize_t ob_exports; /* How many buffer exports */
 } PyByteArrayObject;
 
-/* Macros, trading safety for speed */
-#define PyByteArray_AS_STRING(self) \
-    (assert(PyByteArray_Check(self)), \
-     Py_SIZE(self) ? ((PyByteArrayObject *)(self))->ob_start : _PyByteArray_empty_string)
-#define PyByteArray_GET_SIZE(self) (assert(PyByteArray_Check(self)), Py_SIZE(self))
-
 PyAPI_DATA(char) _PyByteArray_empty_string[];
+
+// Static inline function, trading safety for speed
+static inline char* _PyByteArray_AS_STRING(PyByteArrayObject *self) {
+    assert(PyByteArray_Check(self));
+    if (Py_SIZE(self)) {
+        return self->ob_start;
+    }
+    else {
+        return _PyByteArray_empty_string;
+    }
+}
+#define PyByteArray_AS_STRING(op) _PyByteArray_AS_STRING((PyByteArrayObject *)(op))
+
+// Macro, trading safety for speed
+#define PyByteArray_GET_SIZE(self) (assert(PyByteArray_Check(self)), Py_SIZE(self))
diff --git a/Include/cpython/bytesobject.h b/Include/cpython/bytesobject.h
@@ -28,10 +28,15 @@ PyAPI_FUNC(PyObject*) _PyBytes_FromHex(
 PyAPI_FUNC(PyObject *) _PyBytes_DecodeEscape(const char *, Py_ssize_t,
                                              const char *, const char **);
 
-/* Macro, trading safety for speed */
-#define PyBytes_AS_STRING(op) (assert(PyBytes_Check(op)), \
-                                (((PyBytesObject *)(op))->ob_sval))
-#define PyBytes_GET_SIZE(op)  (assert(PyBytes_Check(op)),Py_SIZE(op))
+// Static inline function, trading safety for speed
+static inline char* _PyBytes_AS_STRING(PyBytesObject *op) {
+    assert(PyBytes_Check(op));
+    return op->ob_sval;
+}
+#define PyBytes_AS_STRING(op) _PyBytes_AS_STRING((PyBytesObject *)(op))
+
+// Macro, trading safety for speed
+#define PyBytes_GET_SIZE(op)  (assert(PyBytes_Check(op)), Py_SIZE(op))
 
 /* _PyBytes_Join(sep, x) is like sep.join(x).  sep must be PyBytesObject*,
    x must be an iterable object. */

diff --git a/Include/cpython/floatobject.h b/Include/cpython/floatobject.h
@@ -7,6 +7,10 @@ typedef struct {
     double ob_fval;
 } PyFloatObject;
 
-// Macro version of PyFloat_AsDouble() trading safety for speed.
-// It doesn't check if op is a double object.
-#define PyFloat_AS_DOUBLE(op) (((PyFloatObject *)(op))->ob_fval)
+// Static inline version of PyFloat_AsDouble() trading safety for speed.
+// It only checks if op is a Python float object in debug mode.
+static inline double _PyFloat_AS_DOUBLE(PyFloatObject *op) {
+    assert(PyFloat_Check(op));
+    return op->ob_fval;
+}
+#define PyFloat_AS_DOUBLE(op) _PyFloat_AS_DOUBLE((PyFloatObject *)(op))
diff --git a/Include/cpython/unicodeobject.h b/Include/cpython/unicodeobject.h
@@ -254,16 +254,9 @@ PyAPI_FUNC(int) _PyUnicode_CheckConsistency(
 #define PyUnicode_GET_DATA_SIZE(op) \
     (PyUnicode_GET_SIZE(op) * Py_UNICODE_SIZE)
 
-/* Alias for PyUnicode_AsUnicode().  This will create a wchar_t/Py_UNICODE
-   representation on demand.  Using this macro is very inefficient now,
-   try to port your code to use the new PyUnicode_*BYTE_DATA() macros or
-   use PyUnicode_WRITE() and PyUnicode_READ(). */
-
+/* Alias for PyUnicode_AsUnicode(). */
 /* Py_DEPRECATED(3.3) */
-#define PyUnicode_AS_UNICODE(op) \
-    (assert(PyUnicode_Check(op)), \
-     (((PyASCIIObject *)(op))->wstr) ? (((PyASCIIObject *)(op))->wstr) : \
-      PyUnicode_AsUnicode(_PyObject_CAST(op)))
+#define PyUnicode_AS_UNICODE(op) PyUnicode_AsUnicode(_PyObject_CAST(op))
 
 /* Py_DEPRECATED(3.3) */
 #define PyUnicode_AS_DATA(op) \

diff --git a/Misc/NEWS.d/next/C API/2021-10-15-01-04-45.bpo-45476.HZmZRH.rst b/Misc/NEWS.d/next/C API/2021-10-15-01-04-45.bpo-45476.HZmZRH.rst
@@ -0,0 +1,9 @@
+Convert the following macros to static inline functions to disallow using
+them as l-value:
+
+* :c:func:`PyByteArray_AS_STRING`
+* :c:func:`PyBytes_AS_STRING`
+* :c:func:`PyFloat_AS_DOUBLE`
+
+Moreover, :c:func:`PyUnicode_AS_UNICODE` becomes an alias to
+:c:func:`PyUnicode_AsUnicode`. Patch by Victor Stinner.