libc/include/malloc.h - platform/bionic - Git at Google

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #pragma once

 /**
  * @file malloc.h
  * @brief Heap memory allocation.
  *
  * [Debugging Native Memory Use](https://source.android.com/devices/tech/debug/native-memory)
  * is the canonical source for documentation on Android's heap debugging
  * features.
  */

 #include <sys/cdefs.h>
 #include <stddef.h>
 #include <stdio.h>

 __BEGIN_DECLS

 #define __BIONIC_ALLOC_SIZE(...) __attribute__((__alloc_size__(__VA_ARGS__)))

 /**
  * [malloc(3)](https://man7.org/linux/man-pages/man3/malloc.3.html) allocates
  * memory on the heap.
  *
  * Returns a pointer to the allocated memory on success and returns a null
  * pointer and sets `errno` on failure.
  *
  * Note that Android (like most Unix systems) allows "overcommit". This
  * allows processes to allocate more memory than the system has, provided
  * they don't use it all. This works because only "dirty" pages that have
  * been written to actually require physical memory. In practice, this
  * means that it's rare to see memory allocation functions return a null
  * pointer, and that a non-null pointer does not mean that you actually
  * have all of the memory you asked for.
  *
  * Note also that the Linux Out Of Memory (OOM) killer behaves differently
  * for code run via `adb shell`. The assumption is that if you ran
  * something via `adb shell` you're a developer who actually wants the
  * device to do what you're asking it to do _even if_ that means killing
  * other processes. Obviously this is not the case for apps, which will
  * be killed in preference to killing other processes.
  */
 __nodiscard void* _Nullable malloc(size_t __byte_count) __mallocfunc __BIONIC_ALLOC_SIZE(1);

 /**
  * [calloc(3)](https://man7.org/linux/man-pages/man3/calloc.3.html) allocates
  * and clears memory on the heap.
  *
  * Returns a pointer to the allocated memory on success and returns a null
  * pointer and sets `errno` on failure (but see the notes for malloc()).
  */
 __nodiscard void* _Nullable calloc(size_t __item_count, size_t __item_size) __mallocfunc __BIONIC_ALLOC_SIZE(1,2);

 /**
  * [realloc(3)](https://man7.org/linux/man-pages/man3/realloc.3.html) resizes
  * allocated memory on the heap.
  *
  * Returns a pointer (which may be different from `__ptr`) to the resized
  * memory on success and returns a null pointer and sets `errno` on failure
  * (but see the notes for malloc()).
  */
 __nodiscard void* _Nullable realloc(void* _Nullable __ptr, size_t __byte_count) __BIONIC_ALLOC_SIZE(2);

 /**
  * [reallocarray(3)](https://man7.org/linux/man-pages/man3/reallocarray.3.html)
  * resizes allocated memory on the heap.
  *
  * Equivalent to `realloc(__ptr, __item_count * __item_size)` but fails if the
  * multiplication overflows.
  *
  * Returns a pointer (which may be different from `__ptr`) to the resized
  * memory on success and returns a null pointer and sets `errno` on failure
  * (but see the notes for malloc()).
  */
 #if __ANDROID_API__ >= 29
 __nodiscard void* _Nullable reallocarray(void* _Nullable __ptr, size_t __item_count, size_t __item_size) __BIONIC_ALLOC_SIZE(2, 3) __INTRODUCED_IN(29);
 #elif defined(__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__)
 #include <errno.h>
 static __inline __nodiscard void* _Nullable reallocarray(void* _Nullable __ptr, size_t __item_count, size_t __item_size) __BIONIC_ALLOC_SIZE(2, 3) {
   size_t __new_size;
   if (__builtin_mul_overflow(__item_count, __item_size, &__new_size)) {
     errno = ENOMEM;
     return NULL;
   }
   return realloc(__ptr, __new_size);
 }
 #endif

 /**
  * [free(3)](https://man7.org/linux/man-pages/man3/free.3.html) deallocates
  * memory on the heap.
  */
 void free(void* _Nullable __ptr);

 /**
  * [memalign(3)](https://man7.org/linux/man-pages/man3/memalign.3.html) allocates
  * memory on the heap with the required alignment.
  *
  * Returns a pointer to the allocated memory on success and returns a null
  * pointer and sets `errno` on failure (but see the notes for malloc()).
  *
  * See also posix_memalign().
  */
 __nodiscard void* _Nullable memalign(size_t __alignment, size_t __byte_count) __mallocfunc __BIONIC_ALLOC_SIZE(2);

 /**
  * [malloc_usable_size(3)](https://man7.org/linux/man-pages/man3/malloc_usable_size.3.html)
  * returns the actual size of the given heap block.
  */
 __nodiscard size_t malloc_usable_size(const void* _Nullable __ptr);

 #define __MALLINFO_BODY \
   /** Total number of non-mmapped bytes currently allocated from OS. */ \
   size_t arena; \
   /** Number of free chunks. */ \
   size_t ordblks; \
   /** (Unused.) */ \
   size_t smblks; \
   /** (Unused.) */ \
   size_t hblks; \
   /** Total number of bytes in mmapped regions. */ \
   size_t hblkhd; \
   /** Maximum total allocated space; greater than total if trimming has occurred. */ \
   size_t usmblks; \
   /** (Unused.) */ \
   size_t fsmblks; \
   /** Total allocated space (normal or mmapped.) */ \
   size_t uordblks; \
   /** Total free space. */ \
   size_t fordblks; \
   /** Upper bound on number of bytes releasable by a trim operation. */ \
   size_t keepcost;

 #ifndef STRUCT_MALLINFO_DECLARED
 #define STRUCT_MALLINFO_DECLARED 1
 struct mallinfo { __MALLINFO_BODY };
 #endif

 /**
  * [mallinfo(3)](https://man7.org/linux/man-pages/man3/mallinfo.3.html) returns
  * information about the current state of the heap. Note that mallinfo() is
  * inherently unreliable and consider using malloc_info() instead.
  */
 struct mallinfo mallinfo(void);

 /**
  * On Android the struct mallinfo and struct mallinfo2 are the same.
  */
 struct mallinfo2 { __MALLINFO_BODY };

 /**
  * [mallinfo2(3)](https://man7.org/linux/man-pages/man3/mallinfo2.3.html) returns
  * information about the current state of the heap. Note that mallinfo2() is
  * inherently unreliable and consider using malloc_info() instead.
  */
 struct mallinfo2 mallinfo2(void) __RENAME(mallinfo);

 /**
  * [malloc_info(3)](https://man7.org/linux/man-pages/man3/malloc_info.3.html)
  * writes information about the current state of the heap to the given stream.
  *
  * The XML structure for malloc_info() is as follows:
  * ```
  * <malloc version="jemalloc-1">
  *   <heap nr="INT">
  *     <allocated-large>INT</allocated-large>
  *     <allocated-huge>INT</allocated-huge>
  *     <allocated-bins>INT</allocated-bins>
  *     <bins-total>INT</bins-total>
  *     <bin nr="INT">
  *       <allocated>INT</allocated>
  *       <nmalloc>INT</nmalloc>
  *       <ndalloc>INT</ndalloc>
  *     </bin>
  *     <!-- more bins -->
  *   </heap>
  *   <!-- more heaps -->
  * </malloc>
  * ```
  *
  * Available since API level 23.
  */

 #if __BIONIC_AVAILABILITY_GUARD(23)
 int malloc_info(int __must_be_zero, FILE* _Nonnull __fp) __INTRODUCED_IN(23);
 #endif /* __BIONIC_AVAILABILITY_GUARD(23) */


 /**
  * mallopt() option to set the decay time. Valid values are -1, 0 and 1.
  *   -1 : Disable the releasing of unused pages. This value is available since
  *        API level 35.
  *    0 : Release the unused pages immediately.
  *    1 : Release the unused pages at a device-specific interval.
  *
  * Available since API level 27.
  */
 #define M_DECAY_TIME (-100)
 /**
  * mallopt() option to immediately purge any memory not in use. This
  * will release the memory back to the kernel. The value is ignored.
  *
  * Available since API level 28.
  */
 #define M_PURGE (-101)
 /**
  * mallopt() option to immediately purge all possible memory back to
  * the kernel. This call can take longer than a normal purge since it
  * examines everything. In some cases, it can take more than twice the
  * time of a M_PURGE call. The value is ignored.
  *
  * Available since API level 34.
  */
 #define M_PURGE_ALL (-104)

 /**
  * mallopt() option to tune the allocator's choice of memory tags to
  * make it more likely that a certain class of memory errors will be
  * detected. This is only relevant if MTE is enabled in this process
  * and ignored otherwise. The value argument should be one of the
  * M_MEMTAG_TUNING_* flags.
  * NOTE: This is only available in scudo.
  *
  * Available since API level 31.
  */
 #define M_MEMTAG_TUNING (-102)

 /**
  * When passed as a value of M_MEMTAG_TUNING mallopt() call, enables
  * deterministic detection of linear buffer overflow and underflow
  * bugs by assigning distinct tag values to adjacent allocations. This
  * mode has a slightly reduced chance to detect use-after-free bugs
  * because only half of the possible tag values are available for each
  * memory location.
  *
  * Please keep in mind that MTE can not detect overflow within the
  * same tag granule (16-byte aligned chunk), and can miss small
  * overflows even in this mode. Such overflow can not be the cause of
  * a memory corruption, because the memory within one granule is never
  * used for multiple allocations.
  */
 #define M_MEMTAG_TUNING_BUFFER_OVERFLOW 0

 /**
  * When passed as a value of M_MEMTAG_TUNING mallopt() call, enables
  * independently randomized tags for uniform ~93% probability of
  * detecting both spatial (buffer overflow) and temporal (use after
  * free) bugs.
  */
 #define M_MEMTAG_TUNING_UAF 1

 /**
  * mallopt() option for per-thread memory initialization tuning.
  * The value argument should be one of:
  * 1: Disable automatic heap initialization on this thread only.
  *    If memory tagging is enabled, disable as much as possible of the
  *    memory tagging initialization for this thread.
  * 0: Normal behavior.
  *
  * Available since API level 31.
  */
 #define M_THREAD_DISABLE_MEM_INIT (-103)
 /**
  * mallopt() option to set the maximum number of items in the secondary
  * cache of the scudo allocator.
  *
  * Available since API level 31.
  */
 #define M_CACHE_COUNT_MAX (-200)
 /**
  * mallopt() option to set the maximum size in bytes of a cacheable item in
  * the secondary cache of the scudo allocator.
  *
  * Available since API level 31.
  */
 #define M_CACHE_SIZE_MAX (-201)
 /**
  * mallopt() option to increase the maximum number of shared thread-specific
  * data structures that can be created. This number cannot be decreased,
  * only increased and only applies to the scudo allocator.
  *
  * Available since API level 31.
  */
 #define M_TSDS_COUNT_MAX (-202)

 /**
  * mallopt() option to decide whether heap memory is zero-initialized on
  * allocation across the whole process. May be called at any time, including
  * when multiple threads are running. An argument of zero indicates memory
  * should not be zero-initialized, any other value indicates to initialize heap
  * memory to zero.
  *
  * Note that this memory mitigation is only implemented in scudo and therefore
  * this will have no effect when using another allocator (such as jemalloc on
  * Android Go devices).
  *
  * Available since API level 31.
  */
 #define M_BIONIC_ZERO_INIT (-203)

 /**
  * mallopt() option to change the heap tagging state. May be called at any
  * time, including when multiple threads are running.
  * The value must be one of the M_HEAP_TAGGING_LEVEL_ constants.
  * NOTE: This is only available in scudo.
  *
  * Available since API level 31.
  */
 #define M_BIONIC_SET_HEAP_TAGGING_LEVEL (-204)

 /**
  * Constants for use with the M_BIONIC_SET_HEAP_TAGGING_LEVEL mallopt() option.
  */
 enum HeapTaggingLevel {
   /**
    * Disable heap tagging and memory tag checks (if supported).
    * Heap tagging may not be re-enabled after being disabled.
    */
   M_HEAP_TAGGING_LEVEL_NONE = 0,
 #define M_HEAP_TAGGING_LEVEL_NONE M_HEAP_TAGGING_LEVEL_NONE
   /**
    * Address-only tagging. Heap pointers have a non-zero tag in the
    * most significant ("top") byte which is checked in free(). Memory
    * accesses ignore the tag using arm64's Top Byte Ignore (TBI) feature.
    */
   M_HEAP_TAGGING_LEVEL_TBI = 1,
 #define M_HEAP_TAGGING_LEVEL_TBI M_HEAP_TAGGING_LEVEL_TBI
   /**
    * Enable heap tagging and asynchronous memory tag checks (if supported).
    * Disable stack trace collection.
    */
   M_HEAP_TAGGING_LEVEL_ASYNC = 2,
 #define M_HEAP_TAGGING_LEVEL_ASYNC M_HEAP_TAGGING_LEVEL_ASYNC
   /**
    * Enable heap tagging and synchronous memory tag checks (if supported).
    * Enable stack trace collection.
    */
   M_HEAP_TAGGING_LEVEL_SYNC = 3,
 #define M_HEAP_TAGGING_LEVEL_SYNC M_HEAP_TAGGING_LEVEL_SYNC
 };

 /**
  * mallopt() option to print human readable statistics about the memory
  * allocator to the log. There is no format for this data, each allocator
  * can use a different format, and the data that is printed can
  * change at any time. This is expected to be used as a debugging aid.
  *
  * Available since API level 35.
  */
 #define M_LOG_STATS (-205)

 /**
  * [mallopt(3)](https://man7.org/linux/man-pages/man3/mallopt.3.html) modifies
  * heap behavior. Values of `__option` are the `M_` constants from this header.
  *
  * Returns 1 on success, 0 on error.
  *
  * Available since API level 26.
  */

 #if __BIONIC_AVAILABILITY_GUARD(26)
 int mallopt(int __option, int __value) __INTRODUCED_IN(26);
 #endif /* __BIONIC_AVAILABILITY_GUARD(26) */


 /**
  * [__malloc_hook(3)](https://man7.org/linux/man-pages/man3/__malloc_hook.3.html)
  * is called to implement malloc(). By default this points to the system's
  * implementation.
  *
  * Available since API level 28.
  *
  * See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
  */

 #if __BIONIC_AVAILABILITY_GUARD(28)
 extern void* _Nonnull (*volatile _Nonnull __malloc_hook)(size_t __byte_count, const void* _Nonnull __caller) __INTRODUCED_IN(28);

 /**
  * [__realloc_hook(3)](https://man7.org/linux/man-pages/man3/__realloc_hook.3.html)
  * is called to implement realloc(). By default this points to the system's
  * implementation.
  *
  * Available since API level 28.
  *
  * See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
  */
 extern void* _Nonnull (*volatile _Nonnull __realloc_hook)(void* _Nullable __ptr, size_t __byte_count, const void* _Nonnull __caller) __INTRODUCED_IN(28);

 /**
  * [__free_hook(3)](https://man7.org/linux/man-pages/man3/__free_hook.3.html)
  * is called to implement free(). By default this points to the system's
  * implementation.
  *
  * Available since API level 28.
  *
  * See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
  */
 extern void (*volatile _Nonnull __free_hook)(void* _Nullable __ptr, const void* _Nonnull __caller) __INTRODUCED_IN(28);

 /**
  * [__memalign_hook(3)](https://man7.org/linux/man-pages/man3/__memalign_hook.3.html)
  * is called to implement memalign(). By default this points to the system's
  * implementation.
  *
  * Available since API level 28.
  *
  * See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
  */
 extern void* _Nonnull (*volatile _Nonnull __memalign_hook)(size_t __alignment, size_t __byte_count, const void* _Nonnull __caller) __INTRODUCED_IN(28);
 #endif /* __BIONIC_AVAILABILITY_GUARD(28) */


 __END_DECLS
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#pragma once

	/**
	* @file malloc.h
	* @brief Heap memory allocation.
	*
	* [Debugging Native Memory Use](https://source.android.com/devices/tech/debug/native-memory)
	* is the canonical source for documentation on Android's heap debugging
	* features.
	*/

	#include <sys/cdefs.h>
	#include <stddef.h>
	#include <stdio.h>

	__BEGIN_DECLS

	#define __BIONIC_ALLOC_SIZE(...) __attribute__((__alloc_size__(__VA_ARGS__)))

	/**
	* [malloc(3)](https://man7.org/linux/man-pages/man3/malloc.3.html) allocates
	* memory on the heap.
	*
	* Returns a pointer to the allocated memory on success and returns a null
	* pointer and sets `errno` on failure.
	*
	* Note that Android (like most Unix systems) allows "overcommit". This
	* allows processes to allocate more memory than the system has, provided
	* they don't use it all. This works because only "dirty" pages that have
	* been written to actually require physical memory. In practice, this
	* means that it's rare to see memory allocation functions return a null
	* pointer, and that a non-null pointer does not mean that you actually
	* have all of the memory you asked for.
	*
	* Note also that the Linux Out Of Memory (OOM) killer behaves differently
	* for code run via `adb shell`. The assumption is that if you ran
	* something via `adb shell` you're a developer who actually wants the
	* device to do what you're asking it to do _even if_ that means killing
	* other processes. Obviously this is not the case for apps, which will
	* be killed in preference to killing other processes.
	*/
	__nodiscard void* _Nullable malloc(size_t __byte_count) __mallocfunc __BIONIC_ALLOC_SIZE(1);

	/**
	* [calloc(3)](https://man7.org/linux/man-pages/man3/calloc.3.html) allocates
	* and clears memory on the heap.
	*
	* Returns a pointer to the allocated memory on success and returns a null
	* pointer and sets `errno` on failure (but see the notes for malloc()).
	*/
	__nodiscard void* _Nullable calloc(size_t __item_count, size_t __item_size) __mallocfunc __BIONIC_ALLOC_SIZE(1,2);

	/**
	* [realloc(3)](https://man7.org/linux/man-pages/man3/realloc.3.html) resizes
	* allocated memory on the heap.
	*
	* Returns a pointer (which may be different from `__ptr`) to the resized
	* memory on success and returns a null pointer and sets `errno` on failure
	* (but see the notes for malloc()).
	*/
	__nodiscard void* _Nullable realloc(void* _Nullable __ptr, size_t __byte_count) __BIONIC_ALLOC_SIZE(2);

	/**
	* [reallocarray(3)](https://man7.org/linux/man-pages/man3/reallocarray.3.html)
	* resizes allocated memory on the heap.
	*
	* Equivalent to `realloc(__ptr, __item_count * __item_size)` but fails if the
	* multiplication overflows.
	*
	* Returns a pointer (which may be different from `__ptr`) to the resized
	* memory on success and returns a null pointer and sets `errno` on failure
	* (but see the notes for malloc()).
	*/
	#if __ANDROID_API__ >= 29
	__nodiscard void* _Nullable reallocarray(void* _Nullable __ptr, size_t __item_count, size_t __item_size) __BIONIC_ALLOC_SIZE(2, 3) __INTRODUCED_IN(29);
	#elif defined(__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__)
	#include <errno.h>
	static __inline __nodiscard void* _Nullable reallocarray(void* _Nullable __ptr, size_t __item_count, size_t __item_size) __BIONIC_ALLOC_SIZE(2, 3) {
	size_t __new_size;
	if (__builtin_mul_overflow(__item_count, __item_size, &__new_size)) {
	errno = ENOMEM;
	return NULL;
	}
	return realloc(__ptr, __new_size);
	}
	#endif

	/**
	* [free(3)](https://man7.org/linux/man-pages/man3/free.3.html) deallocates
	* memory on the heap.
	*/
	void free(void* _Nullable __ptr);

	/**
	* [memalign(3)](https://man7.org/linux/man-pages/man3/memalign.3.html) allocates
	* memory on the heap with the required alignment.
	*
	* Returns a pointer to the allocated memory on success and returns a null
	* pointer and sets `errno` on failure (but see the notes for malloc()).
	*
	* See also posix_memalign().
	*/
	__nodiscard void* _Nullable memalign(size_t __alignment, size_t __byte_count) __mallocfunc __BIONIC_ALLOC_SIZE(2);

	/**
	* [malloc_usable_size(3)](https://man7.org/linux/man-pages/man3/malloc_usable_size.3.html)
	* returns the actual size of the given heap block.
	*/
	__nodiscard size_t malloc_usable_size(const void* _Nullable __ptr);

	#define __MALLINFO_BODY \
	/** Total number of non-mmapped bytes currently allocated from OS. */ \
	size_t arena; \
	/** Number of free chunks. */ \
	size_t ordblks; \
	/** (Unused.) */ \
	size_t smblks; \
	/** (Unused.) */ \
	size_t hblks; \
	/** Total number of bytes in mmapped regions. */ \
	size_t hblkhd; \
	/** Maximum total allocated space; greater than total if trimming has occurred. */ \
	size_t usmblks; \
	/** (Unused.) */ \
	size_t fsmblks; \
	/** Total allocated space (normal or mmapped.) */ \
	size_t uordblks; \
	/** Total free space. */ \
	size_t fordblks; \
	/** Upper bound on number of bytes releasable by a trim operation. */ \
	size_t keepcost;

	#ifndef STRUCT_MALLINFO_DECLARED
	#define STRUCT_MALLINFO_DECLARED 1
	struct mallinfo { __MALLINFO_BODY };
	#endif

	/**
	* [mallinfo(3)](https://man7.org/linux/man-pages/man3/mallinfo.3.html) returns
	* information about the current state of the heap. Note that mallinfo() is
	* inherently unreliable and consider using malloc_info() instead.
	*/
	struct mallinfo mallinfo(void);

	/**
	* On Android the struct mallinfo and struct mallinfo2 are the same.
	*/
	struct mallinfo2 { __MALLINFO_BODY };

	/**
	* [mallinfo2(3)](https://man7.org/linux/man-pages/man3/mallinfo2.3.html) returns
	* information about the current state of the heap. Note that mallinfo2() is
	* inherently unreliable and consider using malloc_info() instead.
	*/
	struct mallinfo2 mallinfo2(void) __RENAME(mallinfo);

	/**
	* [malloc_info(3)](https://man7.org/linux/man-pages/man3/malloc_info.3.html)
	* writes information about the current state of the heap to the given stream.
	*
	* The XML structure for malloc_info() is as follows:
	* ```
	* <malloc version="jemalloc-1">
	* <heap nr="INT">
	* <allocated-large>INT</allocated-large>
	* <allocated-huge>INT</allocated-huge>
	* <allocated-bins>INT</allocated-bins>
	* <bins-total>INT</bins-total>
	* <bin nr="INT">
	* <allocated>INT</allocated>
	* <nmalloc>INT</nmalloc>
	* <ndalloc>INT</ndalloc>
	* </bin>
	* <!-- more bins -->
	* </heap>
	* <!-- more heaps -->
	* </malloc>
	* ```
	*
	* Available since API level 23.
	*/

	#if __BIONIC_AVAILABILITY_GUARD(23)
	int malloc_info(int __must_be_zero, FILE* _Nonnull __fp) __INTRODUCED_IN(23);
	#endif /* __BIONIC_AVAILABILITY_GUARD(23) */


	/**
	* mallopt() option to set the decay time. Valid values are -1, 0 and 1.
	* -1 : Disable the releasing of unused pages. This value is available since
	* API level 35.
	* 0 : Release the unused pages immediately.
	* 1 : Release the unused pages at a device-specific interval.
	*
	* Available since API level 27.
	*/
	#define M_DECAY_TIME (-100)
	/**
	* mallopt() option to immediately purge any memory not in use. This
	* will release the memory back to the kernel. The value is ignored.
	*
	* Available since API level 28.
	*/
	#define M_PURGE (-101)
	/**
	* mallopt() option to immediately purge all possible memory back to
	* the kernel. This call can take longer than a normal purge since it
	* examines everything. In some cases, it can take more than twice the
	* time of a M_PURGE call. The value is ignored.
	*
	* Available since API level 34.
	*/
	#define M_PURGE_ALL (-104)

	/**
	* mallopt() option to tune the allocator's choice of memory tags to
	* make it more likely that a certain class of memory errors will be
	* detected. This is only relevant if MTE is enabled in this process
	* and ignored otherwise. The value argument should be one of the
	* M_MEMTAG_TUNING_* flags.
	* NOTE: This is only available in scudo.
	*
	* Available since API level 31.
	*/
	#define M_MEMTAG_TUNING (-102)

	/**
	* When passed as a value of M_MEMTAG_TUNING mallopt() call, enables
	* deterministic detection of linear buffer overflow and underflow
	* bugs by assigning distinct tag values to adjacent allocations. This
	* mode has a slightly reduced chance to detect use-after-free bugs
	* because only half of the possible tag values are available for each
	* memory location.
	*
	* Please keep in mind that MTE can not detect overflow within the
	* same tag granule (16-byte aligned chunk), and can miss small
	* overflows even in this mode. Such overflow can not be the cause of
	* a memory corruption, because the memory within one granule is never
	* used for multiple allocations.
	*/
	#define M_MEMTAG_TUNING_BUFFER_OVERFLOW 0

	/**
	* When passed as a value of M_MEMTAG_TUNING mallopt() call, enables
	* independently randomized tags for uniform ~93% probability of
	* detecting both spatial (buffer overflow) and temporal (use after
	* free) bugs.
	*/
	#define M_MEMTAG_TUNING_UAF 1

	/**
	* mallopt() option for per-thread memory initialization tuning.
	* The value argument should be one of:
	* 1: Disable automatic heap initialization on this thread only.
	* If memory tagging is enabled, disable as much as possible of the
	* memory tagging initialization for this thread.
	* 0: Normal behavior.
	*
	* Available since API level 31.
	*/
	#define M_THREAD_DISABLE_MEM_INIT (-103)
	/**
	* mallopt() option to set the maximum number of items in the secondary
	* cache of the scudo allocator.
	*
	* Available since API level 31.
	*/
	#define M_CACHE_COUNT_MAX (-200)
	/**
	* mallopt() option to set the maximum size in bytes of a cacheable item in
	* the secondary cache of the scudo allocator.
	*
	* Available since API level 31.
	*/
	#define M_CACHE_SIZE_MAX (-201)
	/**
	* mallopt() option to increase the maximum number of shared thread-specific
	* data structures that can be created. This number cannot be decreased,
	* only increased and only applies to the scudo allocator.
	*
	* Available since API level 31.
	*/
	#define M_TSDS_COUNT_MAX (-202)

	/**
	* mallopt() option to decide whether heap memory is zero-initialized on
	* allocation across the whole process. May be called at any time, including
	* when multiple threads are running. An argument of zero indicates memory
	* should not be zero-initialized, any other value indicates to initialize heap
	* memory to zero.
	*
	* Note that this memory mitigation is only implemented in scudo and therefore
	* this will have no effect when using another allocator (such as jemalloc on
	* Android Go devices).
	*
	* Available since API level 31.
	*/
	#define M_BIONIC_ZERO_INIT (-203)

	/**
	* mallopt() option to change the heap tagging state. May be called at any
	* time, including when multiple threads are running.
	* The value must be one of the M_HEAP_TAGGING_LEVEL_ constants.
	* NOTE: This is only available in scudo.
	*
	* Available since API level 31.
	*/
	#define M_BIONIC_SET_HEAP_TAGGING_LEVEL (-204)

	/**
	* Constants for use with the M_BIONIC_SET_HEAP_TAGGING_LEVEL mallopt() option.
	*/
	enum HeapTaggingLevel {
	/**
	* Disable heap tagging and memory tag checks (if supported).
	* Heap tagging may not be re-enabled after being disabled.
	*/
	M_HEAP_TAGGING_LEVEL_NONE = 0,
	#define M_HEAP_TAGGING_LEVEL_NONE M_HEAP_TAGGING_LEVEL_NONE
	/**
	* Address-only tagging. Heap pointers have a non-zero tag in the
	* most significant ("top") byte which is checked in free(). Memory
	* accesses ignore the tag using arm64's Top Byte Ignore (TBI) feature.
	*/
	M_HEAP_TAGGING_LEVEL_TBI = 1,
	#define M_HEAP_TAGGING_LEVEL_TBI M_HEAP_TAGGING_LEVEL_TBI
	/**
	* Enable heap tagging and asynchronous memory tag checks (if supported).
	* Disable stack trace collection.
	*/
	M_HEAP_TAGGING_LEVEL_ASYNC = 2,
	#define M_HEAP_TAGGING_LEVEL_ASYNC M_HEAP_TAGGING_LEVEL_ASYNC
	/**
	* Enable heap tagging and synchronous memory tag checks (if supported).
	* Enable stack trace collection.
	*/
	M_HEAP_TAGGING_LEVEL_SYNC = 3,
	#define M_HEAP_TAGGING_LEVEL_SYNC M_HEAP_TAGGING_LEVEL_SYNC
	};

	/**
	* mallopt() option to print human readable statistics about the memory
	* allocator to the log. There is no format for this data, each allocator
	* can use a different format, and the data that is printed can
	* change at any time. This is expected to be used as a debugging aid.
	*
	* Available since API level 35.
	*/
	#define M_LOG_STATS (-205)

	/**
	* [mallopt(3)](https://man7.org/linux/man-pages/man3/mallopt.3.html) modifies
	* heap behavior. Values of `__option` are the `M_` constants from this header.
	*
	* Returns 1 on success, 0 on error.
	*
	* Available since API level 26.
	*/

	#if __BIONIC_AVAILABILITY_GUARD(26)
	int mallopt(int __option, int __value) __INTRODUCED_IN(26);
	#endif /* __BIONIC_AVAILABILITY_GUARD(26) */


	/**
	* [__malloc_hook(3)](https://man7.org/linux/man-pages/man3/__malloc_hook.3.html)
	* is called to implement malloc(). By default this points to the system's
	* implementation.
	*
	* Available since API level 28.
	*
	* See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
	*/

	#if __BIONIC_AVAILABILITY_GUARD(28)
	extern void* _Nonnull (volatile _Nonnull __malloc_hook)(size_t __byte_count, const void _Nonnull __caller) __INTRODUCED_IN(28);

	/**
	* [__realloc_hook(3)](https://man7.org/linux/man-pages/man3/__realloc_hook.3.html)
	* is called to implement realloc(). By default this points to the system's
	* implementation.
	*
	* Available since API level 28.
	*
	* See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
	*/
	extern void* _Nonnull (volatile _Nonnull __realloc_hook)(void _Nullable __ptr, size_t __byte_count, const void* _Nonnull __caller) __INTRODUCED_IN(28);

	/**
	* [__free_hook(3)](https://man7.org/linux/man-pages/man3/__free_hook.3.html)
	* is called to implement free(). By default this points to the system's
	* implementation.
	*
	* Available since API level 28.
	*
	* See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
	*/
	extern void (volatile _Nonnull __free_hook)(void _Nullable __ptr, const void* _Nonnull __caller) __INTRODUCED_IN(28);

	/**
	* [__memalign_hook(3)](https://man7.org/linux/man-pages/man3/__memalign_hook.3.html)
	* is called to implement memalign(). By default this points to the system's
	* implementation.
	*
	* Available since API level 28.
	*
	* See also: [extra documentation](https://android.googlesource.com/platform/bionic/+/main/libc/malloc_hooks/README.md)
	*/
	extern void* _Nonnull (volatile _Nonnull __memalign_hook)(size_t __alignment, size_t __byte_count, const void _Nonnull __caller) __INTRODUCED_IN(28);
	#endif /* __BIONIC_AVAILABILITY_GUARD(28) */


	__END_DECLS