mirror of https://github.com/python/cpython.git
171 lines
5.1 KiB
C
171 lines
5.1 KiB
C
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/* Lowest-level memory allocation interface */
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#ifndef Py_PYMEM_H
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#define Py_PYMEM_H
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#include "pyport.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* Core memory allocator
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* =====================
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*/
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/* To make sure the interpreter is user-malloc friendly, all memory
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APIs are implemented on top of this one.
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The PyCore_* macros can be defined to make the interpreter use a
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custom allocator. Note that they are for internal use only. Both
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the core and extension modules should use the PyMem_* API.
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See the comment block at the end of this file for two scenarios
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showing how to use this to use a different allocator. */
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#ifndef PyCore_MALLOC_FUNC
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#undef PyCore_REALLOC_FUNC
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#undef PyCore_FREE_FUNC
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#define PyCore_MALLOC_FUNC malloc
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#define PyCore_REALLOC_FUNC realloc
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#define PyCore_FREE_FUNC free
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#endif
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#ifndef PyCore_MALLOC_PROTO
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#undef PyCore_REALLOC_PROTO
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#undef PyCore_FREE_PROTO
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#define PyCore_MALLOC_PROTO (size_t)
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#define PyCore_REALLOC_PROTO (void *, size_t)
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#define PyCore_FREE_PROTO (void *)
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#endif
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#ifdef NEED_TO_DECLARE_MALLOC_AND_FRIEND
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extern void *PyCore_MALLOC_FUNC PyCore_MALLOC_PROTO;
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extern void *PyCore_REALLOC_FUNC PyCore_REALLOC_PROTO;
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extern void PyCore_FREE_FUNC PyCore_FREE_PROTO;
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#endif
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#ifndef PyCore_MALLOC
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#undef PyCore_REALLOC
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#undef PyCore_FREE
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#define PyCore_MALLOC(n) PyCore_MALLOC_FUNC(n)
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#define PyCore_REALLOC(p, n) PyCore_REALLOC_FUNC((p), (n))
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#define PyCore_FREE(p) PyCore_FREE_FUNC(p)
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#endif
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/* BEWARE:
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Each interface exports both functions and macros. Extension modules
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should normally use the functions for ensuring binary compatibility
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of the user's code across Python versions. Subsequently, if the
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Python runtime switches to its own malloc (different from standard
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malloc), no recompilation is required for the extensions.
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The macro versions trade compatibility for speed. They can be used
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whenever there is a performance problem, but their use implies
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recompilation of the code for each new Python release. The Python
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core uses the macros because it *is* compiled on every upgrade.
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This might not be the case with 3rd party extensions in a custom
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setup (for example, a customer does not always have access to the
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source of 3rd party deliverables). You have been warned! */
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/*
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* Raw memory interface
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* ====================
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*/
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/* Functions */
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/* Function wrappers around PyCore_MALLOC and friends; useful if you
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need to be sure that you are using the same memory allocator as
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Python. Note that the wrappers make sure that allocating 0 bytes
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returns a non-NULL pointer, even if the underlying malloc
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doesn't. Returned pointers must be checked for NULL explicitly.
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No action is performed on failure. */
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extern DL_IMPORT(void *) PyMem_Malloc(size_t);
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extern DL_IMPORT(void *) PyMem_Realloc(void *, size_t);
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extern DL_IMPORT(void) PyMem_Free(void *);
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/* Starting from Python 1.6, the wrappers Py_{Malloc,Realloc,Free} are
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no longer supported. They used to call PyErr_NoMemory() on failure. */
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/* Macros */
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#define PyMem_MALLOC(n) PyCore_MALLOC(n)
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#define PyMem_REALLOC(p, n) PyCore_REALLOC((void *)(p), (n))
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#define PyMem_FREE(p) PyCore_FREE((void *)(p))
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/*
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* Type-oriented memory interface
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* ==============================
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*/
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/* Functions */
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#define PyMem_New(type, n) \
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( (type *) PyMem_Malloc((n) * sizeof(type)) )
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#define PyMem_Resize(p, type, n) \
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( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) )
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#define PyMem_Del(p) PyMem_Free(p)
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/* Macros */
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#define PyMem_NEW(type, n) \
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( (type *) PyMem_MALLOC(_PyMem_EXTRA + (n) * sizeof(type)) )
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#define PyMem_RESIZE(p, type, n) \
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if ((p) == NULL) \
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(p) = (type *)(PyMem_MALLOC( \
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_PyMem_EXTRA + (n) * sizeof(type))); \
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else \
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(p) = (type *)(PyMem_REALLOC((p), \
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_PyMem_EXTRA + (n) * sizeof(type)))
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#define PyMem_DEL(p) PyMem_FREE(p)
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/* PyMem_XDEL is deprecated. To avoid the call when p is NULL,
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it is recommended to write the test explicitly in the code.
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Note that according to ANSI C, free(NULL) has no effect. */
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#ifdef __cplusplus
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}
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#endif
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/* SCENARIOS
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Here are two scenarios by Vladimir Marangozov (the author of the
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memory allocation redesign).
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1) Scenario A
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Suppose you want to use a debugging malloc library that collects info on
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where the malloc calls originate from. Assume the interface is:
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d_malloc(size_t n, char* src_file, unsigned long src_line) c.s.
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In this case, you would define (for example in pyconfig.h) :
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#define PyCore_MALLOC_FUNC d_malloc
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...
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#define PyCore_MALLOC_PROTO (size_t, char *, unsigned long)
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...
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#define NEED_TO_DECLARE_MALLOC_AND_FRIEND
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#define PyCore_MALLOC(n) PyCore_MALLOC_FUNC((n), __FILE__, __LINE__)
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...
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2) Scenario B
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Suppose you want to use malloc hooks (defined & initialized in a 3rd party
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malloc library) instead of malloc functions. In this case, you would
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define:
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#define PyCore_MALLOC_FUNC (*malloc_hook)
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...
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#define NEED_TO_DECLARE_MALLOC_AND_FRIEND
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and ignore the previous definitions about PyCore_MALLOC_FUNC, etc.
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*/
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#endif /* !Py_PYMEM_H */
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