Include/pymem.h

   1 /* The PyMem_ family:  low-level memory allocation interfaces.
   2    See objimpl.h for the PyObject_ memory family.
   3 */
   4
   5 #ifndef Py_PYMEM_H
   6 #define Py_PYMEM_H
   7
   8 #include "pyport.h"
   9
  10 #ifdef __cplusplus
  11 extern "C" {
  12 #endif
  13
  14 /* BEWARE:
  15
  16    Each interface exports both functions and macros.  Extension modules should
  17    use the functions, to ensure binary compatibility across Python versions.
  18    Because the Python implementation is free to change internal details, and
  19    the macros may (or may not) expose details for speed, if you do use the
  20    macros you must recompile your extensions with each Python release.
  21
  22    Never mix calls to PyMem_ with calls to the platform malloc/realloc/
  23    calloc/free.  For example, on Windows different DLLs may end up using
  24    different heaps, and if you use PyMem_Malloc you'll get the memory from the
  25    heap used by the Python DLL; it could be a disaster if you free()'ed that
  26    directly in your own extension.  Using PyMem_Free instead ensures Python
  27    can return the memory to the proper heap.  As another example, in
  28    PYMALLOC_DEBUG mode, Python wraps all calls to all PyMem_ and PyObject_
  29    memory functions in special debugging wrappers that add additional
  30    debugging info to dynamic memory blocks.  The system routines have no idea
  31    what to do with that stuff, and the Python wrappers have no idea what to do
  32    with raw blocks obtained directly by the system routines then.
  33 */
  34
  35 /*
  36  * Raw memory interface
  37  * ====================
  38  */
  39
  40 /* Functions
  41
  42    Functions supplying platform-independent semantics for malloc/realloc/
  43    free.  These functions make sure that allocating 0 bytes returns a distinct
  44    non-NULL pointer (whenever possible -- if we're flat out of memory, NULL
  45    may be returned), even if the platform malloc and realloc don't.
  46    Returned pointers must be checked for NULL explicitly.  No action is
  47    performed on failure (no exception is set, no warning is printed, etc).
  48 */
  49
  50 PyAPI_FUNC(void *) PyMem_Malloc(size_t);
  51 PyAPI_FUNC(void *) PyMem_Realloc(void *, size_t);
  52 PyAPI_FUNC(void) PyMem_Free(void *);
  53
  54 /* Starting from Python 1.6, the wrappers Py_{Malloc,Realloc,Free} are
  55    no longer supported. They used to call PyErr_NoMemory() on failure. */
  56
  57 /* Macros. */
  58 #ifdef PYMALLOC_DEBUG
  59 /* Redirect all memory operations to Python's debugging allocator. */
  60 #define PyMem_MALLOC            PyObject_MALLOC
  61 #define PyMem_REALLOC           PyObject_REALLOC
  62
  63 #else   /* ! PYMALLOC_DEBUG */
  64
  65 #ifdef MALLOC_ZERO_RETURNS_NULL
  66 #define PyMem_MALLOC(n)         malloc((n) ? (n) : 1)
  67 #else
  68 #define PyMem_MALLOC            malloc
  69 #endif
  70
  71 /* Caution:  whether MALLOC_ZERO_RETURNS_NULL is #defined has nothing to
  72    do with whether platform realloc(non-NULL, 0) normally frees the memory
  73    or returns NULL.  Rather than introduce yet another config variation,
  74    just make a realloc to 0 bytes act as if to 1 instead. */
  75 #define PyMem_REALLOC(p, n)     realloc((p), (n) ? (n) : 1)
  76
  77 #endif  /* PYMALLOC_DEBUG */
  78
  79 /* In order to avoid breaking old code mixing PyObject_{New, NEW} with
  80    PyMem_{Del, DEL} and PyMem_{Free, FREE}, the PyMem "release memory"
  81    functions have to be redirected to the object deallocator. */
  82 #define PyMem_FREE              PyObject_FREE
  83
  84 /*
  85  * Type-oriented memory interface
  86  * ==============================
  87  *
  88  * These are carried along for historical reasons.  There's rarely a good
  89  * reason to use them anymore (you can just as easily do the multiply and
  90  * cast yourself).
  91  */
  92
  93 #define PyMem_New(type, n) \
  94         ( (type *) PyMem_Malloc((n) * sizeof(type)) )
  95 #define PyMem_NEW(type, n) \
  96         ( (type *) PyMem_MALLOC((n) * sizeof(type)) )
  97
  98 #define PyMem_Resize(p, type, n) \
  99         ( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) )
 100 #define PyMem_RESIZE(p, type, n) \
 101         ( (p) = (type *) PyMem_REALLOC((p), (n) * sizeof(type)) )
 102
 103 /* In order to avoid breaking old code mixing PyObject_{New, NEW} with
 104    PyMem_{Del, DEL} and PyMem_{Free, FREE}, the PyMem "release memory"
 105    functions have to be redirected to the object deallocator. */
 106 #define PyMem_Del               PyObject_Free
 107 #define PyMem_DEL               PyObject_FREE
 108
 109 #ifdef __cplusplus
 110 }
 111 #endif
 112
 113 #endif /* !Py_PYMEM_H */