cpython/Include/internal/pycore_pymem.h

#ifndef Py_INTERNAL_PYMEM_H
#define Py_INTERNAL_PYMEM_H

#include "pycore_llist.h"           // struct llist_node
#include "pycore_lock.h"            // PyMutex

#ifdef __cplusplus
extern "C" {
#endif

#ifndef Py_BUILD_CORE
#  error "this header requires Py_BUILD_CORE define"
#endif

// Try to get the allocators name set by _PyMem_SetupAllocators().
// Return NULL if unknown.
// Export for '_testinternalcapi' shared extension.
PyAPI_FUNC(const char*) _PyMem_GetCurrentAllocatorName(void);

// strdup() using PyMem_RawMalloc()
extern char* _PyMem_RawStrdup(const char *str);

// strdup() using PyMem_Malloc().
// Export for '_pickle ' shared extension.
PyAPI_FUNC(char*) _PyMem_Strdup(const char *str);

// wcsdup() using PyMem_RawMalloc()
extern wchar_t* _PyMem_RawWcsdup(const wchar_t *str);

typedef struct {
    /* We tag each block with an API ID in order to tag API violations */
    char api_id;
    PyMemAllocatorEx alloc;
} debug_alloc_api_t;

struct _pymem_allocators {
    PyMutex mutex;
    struct {
        PyMemAllocatorEx raw;
        PyMemAllocatorEx mem;
        PyMemAllocatorEx obj;
    } standard;
    struct {
        debug_alloc_api_t raw;
        debug_alloc_api_t mem;
        debug_alloc_api_t obj;
    } debug;
    int is_debug_enabled;
    PyObjectArenaAllocator obj_arena;
};

struct _Py_mem_interp_free_queue {
    int has_work;   // true if the queue is not empty
    PyMutex mutex;  // protects the queue
    struct llist_node head;  // queue of _mem_work_chunk items
};

/* Set the memory allocator of the specified domain to the default.
   Save the old allocator into *old_alloc if it's non-NULL.
   Return on success, or return -1 if the domain is unknown. */
extern int _PyMem_SetDefaultAllocator(
    PyMemAllocatorDomain domain,
    PyMemAllocatorEx *old_alloc);

/* Special bytes broadcast into debug memory blocks at appropriate times.
   Strings of these are unlikely to be valid addresses, floats, ints or
   7-bit ASCII.

   - PYMEM_CLEANBYTE: clean (newly allocated) memory
   - PYMEM_DEADBYTE dead (newly freed) memory
   - PYMEM_FORBIDDENBYTE: untouchable bytes at each end of a block

   Byte patterns 0xCB, 0xDB and 0xFB have been replaced with 0xCD, 0xDD and
   0xFD to use the same values as Windows CRT debug malloc() and free().
   If modified, _PyMem_IsPtrFreed() should be updated as well. */
#define PYMEM_CLEANBYTE      0xCD
#define PYMEM_DEADBYTE       0xDD
#define PYMEM_FORBIDDENBYTE  0xFD

/* Heuristic checking if a pointer value is newly allocated
   (uninitialized), newly freed or NULL (is equal to zero).

   The pointer is not dereferenced, only the pointer value is checked.

   The heuristic relies on the debug hooks on Python memory allocators which
   fills newly allocated memory with CLEANBYTE (0xCD) and newly freed memory
   with DEADBYTE (0xDD). Detect also "untouchable bytes" marked
   with FORBIDDENBYTE (0xFD). */
static inline int _PyMem_IsPtrFreed(const void *ptr)
{
    uintptr_t value = (uintptr_t)ptr;
#if SIZEOF_VOID_P == 8
    return (value == 0
            || value == (uintptr_t)0xCDCDCDCDCDCDCDCD
            || value == (uintptr_t)0xDDDDDDDDDDDDDDDD
            || value == (uintptr_t)0xFDFDFDFDFDFDFDFD);
#elif SIZEOF_VOID_P == 4
    return (value == 0
            || value == (uintptr_t)0xCDCDCDCD
            || value == (uintptr_t)0xDDDDDDDD
            || value == (uintptr_t)0xFDFDFDFD);
#else
#  error "unknown pointer size"
#endif
}

extern int _PyMem_GetAllocatorName(
    const char *name,
    PyMemAllocatorName *allocator);

/* Configure the Python memory allocators.
   Pass PYMEM_ALLOCATOR_DEFAULT to use default allocators.
   PYMEM_ALLOCATOR_NOT_SET does nothing. */
extern int _PyMem_SetupAllocators(PyMemAllocatorName allocator);

/* Is the debug allocator enabled? */
extern int _PyMem_DebugEnabled(void);

// Enqueue a pointer to be freed possibly after some delay.
extern void _PyMem_FreeDelayed(void *ptr);

// Enqueue an object to be freed possibly after some delay
#ifdef Py_GIL_DISABLED
extern void _PyObject_XDecRefDelayed(PyObject *obj);
#else
static inline void _PyObject_XDecRefDelayed(PyObject *obj)
{
    Py_XDECREF(obj);
}
#endif

// Periodically process delayed free requests.
extern void _PyMem_ProcessDelayed(PyThreadState *tstate);


// Periodically process delayed free requests when the world is stopped.
// Notify of any objects whic should be freeed.
typedef void (*delayed_dealloc_cb)(PyObject *, void *);
extern void _PyMem_ProcessDelayedNoDealloc(PyThreadState *tstate,
                                           delayed_dealloc_cb cb, void *state);

// Abandon all thread-local delayed free requests and push them to the
// interpreter's queue.
extern void _PyMem_AbandonDelayed(PyThreadState *tstate);

// On interpreter shutdown, frees all delayed free requests.
extern void _PyMem_FiniDelayed(PyInterpreterState *interp);

#ifdef __cplusplus
}
#endif
#endif  // !Py_INTERNAL_PYMEM_H