diff options
Diffstat (limited to 'Include/objimpl.h')
| -rw-r--r-- | Include/objimpl.h | 46 |
1 files changed, 35 insertions, 11 deletions
diff --git a/Include/objimpl.h b/Include/objimpl.h index e24d42e..2ea3ad5 100644 --- a/Include/objimpl.h +++ b/Include/objimpl.h @@ -56,14 +56,14 @@ form of memory management you're using). Unless you have specific memory management requirements, it is recommended to use PyObject_{New, NewVar, Del}. */ -/* +/* * Core object memory allocator * ============================ */ /* The purpose of the object allocator is to make the distinction between "object memory" and the rest within the Python heap. - + Object memory is the one allocated by PyObject_{New, NewVar}, i.e. the one that holds the object's representation defined by its C type structure, *excluding* any object-specific memory buffers that @@ -172,16 +172,41 @@ extern DL_IMPORT(void) _PyObject_Del(PyObject *); ( (op)->ob_size = (size), PyObject_INIT((op), (typeobj)) ) #define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize ) -#define _PyObject_VAR_SIZE(typeobj, n) \ - ( (typeobj)->tp_basicsize + (n) * (typeobj)->tp_itemsize ) + +/* _PyObject_VAR_SIZE computes the amount of memory allocated for a vrbl- + size object with nitems items, exclusive of gc overhead (if any). The + value is rounded up to the closest multiple of sizeof(void *), in order + to ensure that pointer fields at the end of the object are correctly + aligned for the platform (this is of special importance for subclasses + of, e.g., str or long, so that pointers can be stored after the embedded + data). + + Note that there's no memory wastage in doing this, as malloc has to + return (at worst) pointer-aligned memory anyway + + However, writing the macro to *return* the result is clumsy due to the + calculations needed. Instead you must pass the result lvalue as the first + argument, and it should be of type size_t (both because that's the + correct conceptual type, and because using an unsigned type allows the + compiler to generate faster code for the mod computation inside the + macro). +*/ +#define _PyObject_VAR_SIZE(result, typeobj, nitems) \ + do { \ + size_t mod; \ + (result) = (size_t) (typeobj)->tp_basicsize; \ + (result) += (size_t) ((nitems)*(typeobj)->tp_itemsize); \ + mod = (result) % SIZEOF_VOID_P; \ + if (mod) \ + (result) += SIZEOF_VOID_P - mod; \ + } while(0) #define PyObject_NEW(type, typeobj) \ ( (type *) PyObject_Init( \ (PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) ) -#define PyObject_NEW_VAR(type, typeobj, n) \ -( (type *) PyObject_InitVar( \ - (PyVarObject *) PyObject_MALLOC( _PyObject_VAR_SIZE((typeobj),(n)) ),\ - (typeobj), (n)) ) + +#define PyObject_NEW_VAR(type, typeobj, nitems) \ + ((type *) _PyObject_NewVar(typeobj, nitems)) #define PyObject_DEL(op) PyObject_FREE(op) @@ -230,8 +255,7 @@ extern DL_IMPORT(void) _PyObject_Del(PyObject *); #define PyObject_IS_GC(o) (PyType_IS_GC((o)->ob_type) && \ ((o)->ob_type->tp_is_gc == NULL || (o)->ob_type->tp_is_gc(o))) -extern DL_IMPORT(PyObject *) _PyObject_GC_Malloc(PyTypeObject *, - int nitems, size_t padding); +extern DL_IMPORT(PyObject *) _PyObject_GC_Malloc(PyTypeObject *, int); extern DL_IMPORT(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, int); #define PyObject_GC_Resize(type, op, n) \ @@ -276,7 +300,7 @@ extern PyGC_Head _PyGC_generation0; #define PyObject_GC_Track(op) _PyObject_GC_Track((PyObject *)op) #define PyObject_GC_UnTrack(op) _PyObject_GC_UnTrack((PyObject *)op) - + #define PyObject_GC_New(type, typeobj) \ ( (type *) _PyObject_GC_New(typeobj) ) |