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bpo-45476: Add _Py_RVALUE() macro (GH-29860)

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Add a new _Py_RVALUE() macro to prevent using an expression as an
l-value.

Replace a "(void)" cast with the _Py_RVALUE() macro in the following
macros:

* PyCell_SET()
* PyList_SET_ITEM()
* PyTuple_SET_ITEM()
* _PyGCHead_SET_FINALIZED()
* _PyGCHead_SET_NEXT()
* asdl_seq_SET()
* asdl_seq_SET_UNTYPED()

Add also parentheses around macro arguments in PyCell_SET() and
PyTuple_SET_ITEM() macros.
This commit is contained in:
Victor Stinner 2021-11-30 12:14:45 +01:00 committed by GitHub
parent f97ec09baf
commit c19c3a0961
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 11 additions and 7 deletions
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2
Include/cpython/cellobject.h
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@ -22,7 +22,7 @@ PyAPI_FUNC(PyObject *) PyCell_Get(PyObject *);
PyAPI_FUNC(int) PyCell_Set(PyObject *, PyObject *);
#define PyCell_GET(op) (((PyCellObject *)(op))->ob_ref)
#define PyCell_SET(op, v) ((void)(((PyCellObject *)(op))->ob_ref = v))
#define PyCell_SET(op, v) _Py_RVALUE(((PyCellObject *)(op))->ob_ref = (v))
#ifdef __cplusplus
}

2
Include/cpython/listobject.h
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@ -30,5 +30,5 @@ PyAPI_FUNC(void) _PyList_DebugMallocStats(FILE *out);
#define _PyList_CAST(op) (assert(PyList_Check(op)), (PyListObject *)(op))
#define PyList_GET_ITEM(op, i) (_PyList_CAST(op)->ob_item[i])
#define PyList_SET_ITEM(op, i, v) ((void)(_PyList_CAST(op)->ob_item[i] = (v)))
#define PyList_SET_ITEM(op, i, v) _Py_RVALUE(_PyList_CAST(op)->ob_item[i] = (v))
#define PyList_GET_SIZE(op) Py_SIZE(_PyList_CAST(op))

2
Include/cpython/tupleobject.h
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@ -23,6 +23,6 @@ PyAPI_FUNC(void) _PyTuple_MaybeUntrack(PyObject *);
#define PyTuple_GET_ITEM(op, i) (_PyTuple_CAST(op)->ob_item[i])
/* Macro, *only* to be used to fill in brand new tuples */
#define PyTuple_SET_ITEM(op, i, v) ((void)(_PyTuple_CAST(op)->ob_item[i] = v))
#define PyTuple_SET_ITEM(op, i, v) _Py_RVALUE(_PyTuple_CAST(op)->ob_item[i] = (v))
PyAPI_FUNC(void) _PyTuple_DebugMallocStats(FILE *out);

4
Include/internal/pycore_asdl.h
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@ -91,7 +91,7 @@ asdl_ ## NAME ## _seq *_Py_asdl_ ## NAME ## _seq_new(Py_ssize_t size, PyArena *a
(S)->typed_elements[_asdl_i] = (V); \
} while (0)
#else
# define asdl_seq_SET(S, I, V) ((void)((S)->typed_elements[I] = (V)))
# define asdl_seq_SET(S, I, V) _Py_RVALUE((S)->typed_elements[I] = (V))
#endif
#ifdef Py_DEBUG
@ -103,7 +103,7 @@ asdl_ ## NAME ## _seq *_Py_asdl_ ## NAME ## _seq_new(Py_ssize_t size, PyArena *a
(S)->elements[_asdl_i] = (V); \
} while (0)
#else
# define asdl_seq_SET_UNTYPED(S, I, V) ((void)((S)->elements[I] = (V)))
# define asdl_seq_SET_UNTYPED(S, I, V) _Py_RVALUE((S)->elements[I] = (V))
#endif
#ifdef __cplusplus

4
Include/internal/pycore_gc.h
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@ -43,7 +43,7 @@ typedef struct {
// Lowest bit of _gc_next is used for flags only in GC.
// But it is always 0 for normal code.
#define _PyGCHead_NEXT(g) ((PyGC_Head*)(g)->_gc_next)
#define _PyGCHead_SET_NEXT(g, p) ((void)((g)->_gc_next = (uintptr_t)(p)))
#define _PyGCHead_SET_NEXT(g, p) _Py_RVALUE((g)->_gc_next = (uintptr_t)(p))
// Lowest two bits of _gc_prev is used for _PyGC_PREV_MASK_* flags.
#define _PyGCHead_PREV(g) ((PyGC_Head*)((g)->_gc_prev & _PyGC_PREV_MASK))
@ -56,7 +56,7 @@ typedef struct {
#define _PyGCHead_FINALIZED(g) \
(((g)->_gc_prev & _PyGC_PREV_MASK_FINALIZED) != 0)
#define _PyGCHead_SET_FINALIZED(g) \
((void)((g)->_gc_prev |= _PyGC_PREV_MASK_FINALIZED))
_Py_RVALUE((g)->_gc_prev |= _PyGC_PREV_MASK_FINALIZED)
#define _PyGC_FINALIZED(o) \
_PyGCHead_FINALIZED(_Py_AS_GC(o))

4
Include/pymacro.h
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@ -129,4 +129,8 @@
Py_FatalError("Unreachable C code path reached")
#endif
// Prevent using an expression as a l-value.
// For example, "int x; _Py_RVALUE(x) = 1;" fails with a compiler error.
#define _Py_RVALUE(EXPR) ((void)0, (EXPR))
#endif /* Py_PYMACRO_H */