[lttng-tools.git] / src / common / macros.hpp

/*
 * Copyright (C) 2011 EfficiOS Inc.
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#ifndef _MACROS_H
#define _MACROS_H

#include <common/compat/string.hpp>

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

#include <memory>
#include <pthread.h>
#include <type_traits>

/*
 * Takes a pointer x and transform it so we can use it to access members
 * without a function call. Here an example:
 *
 *    #define GET_SIZE(x) LTTNG_REF(x)->size
 *
 *    struct { int size; } s;
 *
 *    printf("size : %d\n", GET_SIZE(&s));
 *
 * For this example we can't use something like this for compatibility purpose
 * since this will fail:
 *
 *    #define GET_SIZE(x) x->size;
 *
 * This is mostly use for the compatibility layer of lttng-tools. See
 * poll/epoll for a good example. Since x can be on the stack or allocated
 * memory using malloc(), we must use generic accessors for compat in order to
 * *not* use a function to access members and not the variable name.
 */
#define LTTNG_REF(x) ((typeof(*(x)) *) (x))

#ifdef NDEBUG
/*
* Force usage of the assertion condition to prevent unused variable warnings
* when `assert()` are disabled by the `NDEBUG` definition.
*/
# define LTTNG_ASSERT(_cond) ((void) sizeof((void) (_cond), 0))
#else
# include <assert.h>
# define LTTNG_ASSERT(_cond) assert(_cond)
#endif

/*
 * Memory allocation zeroed
 */

static inline
void *zmalloc_internal(size_t size)
{
	return calloc(1, size);
}

template <typename MallocableType>
struct can_malloc {
	/*
	 * gcc versions before 5.0 lack some type traits defined in C++11.
	 * Since in this instance we use the trait to prevent misuses
	 * of malloc (and statically assert) and not to generate different
	 * code based on this property, simply set value to true and allow
	 * the code to compile. Anyone using a contemporary compiler will
	 * catch the error.
	 */
#if __GNUG__ && __GNUC__ < 5
	static constexpr bool value = true;
#else
	static constexpr bool value = std::is_trivially_constructible<MallocableType>::value;
#endif
};

/*
 * Malloc and zero-initialize an object of type T, asserting that MallocableType can be
 * safely malloc-ed (is trivially constructible).
 */
template <typename MallocableType>
MallocableType *zmalloc()
{
	static_assert(can_malloc<MallocableType>::value, "type can be malloc'ed");
	return (MallocableType *) zmalloc_internal(sizeof(MallocableType)); /* NOLINT sizeof
									       potentially used on a
									       pointer. */
}

/*
 * Malloc and zero-initialize a buffer of size `size`, asserting that type AllocatedType
 * can be safely malloc-ed (is trivially constructible).
 */
template <typename AllocatedType>
AllocatedType *zmalloc(size_t size)
{
	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	LTTNG_ASSERT(size >= sizeof(AllocatedType));
	return (AllocatedType *) zmalloc_internal(size);
}

/*
 * Malloc and zero-initialize an array of `nmemb` elements of type AllocatedType,
 * asserting that AllocatedType can be safely malloc-ed (is trivially constructible).
 */
template <typename AllocatedType>
AllocatedType *calloc(size_t nmemb)
{
	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	return (AllocatedType *) zmalloc_internal(nmemb * sizeof(AllocatedType)); /* NOLINT sizeof
										     potentially
										     used on a
										     pointer. */
}

/*
 * Malloc an object of type AllocatedType, asserting that AllocatedType can be safely malloc-ed (is
 * trivially constructible).
 */
template <typename AllocatedType>
AllocatedType *malloc()
{
	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	return (AllocatedType *) malloc(sizeof(AllocatedType));
}

/*
 * Malloc a buffer of size `size`, asserting that AllocatedType can be safely
 * malloc-ed (is trivially constructible).
 */
template<typename AllocatedType>
AllocatedType *malloc(size_t size)
{
	static_assert (can_malloc<AllocatedType>::value, "type can be malloc'ed");
	return (AllocatedType *) malloc(size);
}

/*
 * Prevent using `free` on types that are non-POD.
 *
 * Declare a delete prototype of free if the parameter type is not safe to free
 * (non-POD).
 *
 * If the parameter is a pointer to void, we can't check if what is pointed
 * to is safe to free or not, as we don't know what is pointed to.  Ideally,
 * all calls to free would be with a typed pointer, but there are too many
 * instances of passing a pointer to void to enforce that right now.  So allow
 * pointers to void, these will not be checked.
 */

template<typename FreedType>
struct can_free
{
	/*
	 * gcc versions before 5.0 lack some type traits defined in C++11.
	 * Since in this instance we use the trait to prevent misuses
	 * of free (and statically assert) and not to generate different
	 * code based on this property, simply set value to true and allow
	 * the code to compile. Anyone using a contemporary compiler will
	 * catch the error.
	 */
#if __GNUG__ && __GNUC__ < 5
	static constexpr bool value = true;
#else
	static constexpr bool value = std::is_trivially_destructible<FreedType>::value ||
		std::is_void<FreedType>::value;
#endif
};

template <typename FreedType, typename = typename std::enable_if<!can_free<FreedType>::value>::type>
void free(FreedType *p) = delete;

template <typename InitializedType>
struct can_memset {
	static constexpr bool value = std::is_pod<InitializedType>::value ||
		std::is_void<InitializedType>::value;
};

template <typename InitializedType,
	  typename = typename std::enable_if<!can_memset<InitializedType>::value>::type>
void *memset(InitializedType *s, int c, size_t n) = delete;

template<typename T>
struct can_memcpy
{
	/*
	 * gcc versions before 5.0 lack some type traits defined in C++11.
	 * Since in this instance we use the trait to prevent misuses
	 * of memcpy (and statically assert) and not to generate different
	 * code based on this property, simply set value to true and allow
	 * the code to compile. Anyone using a contemporary compiler will
	 * catch the error.
	 */
#if __GNUG__ && __GNUC__ < 5
	static constexpr bool value = true;
#else
	static constexpr bool value = std::is_trivially_copyable<T>::value;
#endif
};

template <typename DestinationType,
	  typename SourceType,
	  typename = typename std::enable_if<!can_memcpy<DestinationType>::value>::type,
	  typename = typename std::enable_if<!can_memcpy<SourceType>::value>::type>
void *memcpy(DestinationType *d, const SourceType *s, size_t n) = delete;

template <typename MovedType>
struct can_memmove {
	/*
	 * gcc versions before 5.0 lack some type traits defined in C++11.
	 * Since in this instance we use the trait to prevent misuses
	 * of memmove (and statically assert) and not to generate different
	 * code based on this property, simply set value to true and allow
	 * the code to compile. Anyone using a contemporary compiler will
	 * catch the error.
	 */
#if __GNUG__ && __GNUC__ < 5
	static constexpr bool value = true;
#else
	static constexpr bool value = std::is_trivially_copyable<MovedType>::value;
#endif
};

template <typename DestinationType,
	  typename SourceType,
	  typename = typename std::enable_if<!can_memmove<DestinationType>::value>::type,
	  typename = typename std::enable_if<!can_memmove<SourceType>::value>::type>
void *memmove(DestinationType *d, const SourceType *s, size_t n) = delete;

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(array)   (sizeof(array) / (sizeof((array)[0])))
#endif

#ifndef LTTNG_PACKED
#define LTTNG_PACKED __attribute__((__packed__))
#endif

#ifndef LTTNG_NO_SANITIZE_ADDRESS
#if defined(__clang__) || defined (__GNUC__)
#define LTTNG_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
#else
#define LTTNG_NO_SANITIZE_ADDRESS
#endif
#endif

#define member_sizeof(type, field)	sizeof(((type *) 0)->field)

#define ASSERT_LOCKED(lock)	     LTTNG_ASSERT(pthread_mutex_trylock(&(lock)))
#define ASSERT_RCU_READ_LOCKED() LTTNG_ASSERT(rcu_read_ongoing())
#define ASSERT_RCU_READ_UNLOCKED() LTTNG_ASSERT(!rcu_read_ongoing())

/* Attribute suitable to tag functions as having printf()-like arguments. */
#define ATTR_FORMAT_PRINTF(_string_index, _first_to_check) \
	__attribute__((format(printf, _string_index, _first_to_check)))

/* Attribute suitable to tag functions as having strftime()-like arguments. */
#define ATTR_FORMAT_STRFTIME(_string_index) \
	__attribute__((format(strftime, _string_index, 0)))

/* Macros used to ignore specific compiler diagnostics. */

#define DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
#define DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")

#if defined(__clang__)
  /* Clang */
# define DIAGNOSTIC_IGNORE_SUGGEST_ATTRIBUTE_FORMAT
# define DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL \
	_Pragma("GCC diagnostic ignored \"-Wformat-nonliteral\"")
# define DIAGNOSTIC_IGNORE_LOGICAL_OP
# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES
# define DIAGNOSTIC_IGNORE_INVALID_OFFSETOF
	_Pragma("GCC diagnostic ignored \"-Winvalid-offsetof\"")
#else
  /* GCC */
# define DIAGNOSTIC_IGNORE_SUGGEST_ATTRIBUTE_FORMAT \
	_Pragma("GCC diagnostic ignored \"-Wsuggest-attribute=format\"")
# define DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL \
	_Pragma("GCC diagnostic ignored \"-Wformat-nonliteral\"")
# define DIAGNOSTIC_IGNORE_LOGICAL_OP \
	_Pragma("GCC diagnostic ignored \"-Wlogical-op\"")
#if __GNUG__ && __GNUC__ >= 7
# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES				\
	_Pragma("GCC diagnostic ignored \"-Wduplicated-branches\"")
#else
# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES
#endif /* __GNUG__ && __GNUC__ >= 7 */
# define DIAGNOSTIC_IGNORE_INVALID_OFFSETOF				\
	_Pragma("GCC diagnostic ignored \"-Winvalid-offsetof\"")
#endif

/* Used to make specific C++ functions to C code. */
#ifdef __cplusplus
#define C_LINKAGE extern "C"
#else
#define C_LINKAGE
#endif

/*
 * lttng_strncpy returns 0 on success, or nonzero on failure.
 * It checks that the @src string fits into @dst_len before performing
 * the copy. On failure, no copy has been performed.
 *
 * Assumes that 'src' is null-terminated.
 *
 * dst_len includes the string's trailing NULL.
 */
static inline
int lttng_strncpy(char *dst, const char *src, size_t dst_len)
{
	if (strlen(src) >= dst_len) {
		/* Fail since copying would result in truncation. */
		return -1;
	}
	strcpy(dst, src);
	return 0;
}

namespace lttng {
namespace utils {
template <class ParentType, class MemberType>
ParentType *container_of(const MemberType *member, const MemberType ParentType::*ptr_to_member)
{
	const ParentType *dummy_parent = nullptr;
	auto *offset_of_member = reinterpret_cast<const char *>(&(dummy_parent->*ptr_to_member));
	auto address_of_parent = reinterpret_cast<const char *>(member) - offset_of_member;

	return reinterpret_cast<ParentType *>(address_of_parent);
}
} /* namespace utils */
} /* namespace lttng */

#endif /* _MACROS_H */
Commit	Line	Data
	1	/*
	2	* Copyright (C) 2011 EfficiOS Inc.
	3	* Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*
	5	* SPDX-License-Identifier: GPL-2.0-only
	6	*
	7	*/
	8
	9	#ifndef _MACROS_H
	10	#define _MACROS_H
	11
	12	#include <common/compat/string.hpp>
	13
	14	#include <stddef.h>
	15	#include <stdlib.h>
	16	#include <string.h>
	17
	18	#include <memory>
	19	#include <pthread.h>
	20	#include <type_traits>
	21
	22	/*
	23	* Takes a pointer x and transform it so we can use it to access members
	24	* without a function call. Here an example:
	25	*
	26	* #define GET_SIZE(x) LTTNG_REF(x)->size
	27	*
	28	* struct { int size; } s;
	29	*
	30	* printf("size : %d\n", GET_SIZE(&s));
	31	*
	32	* For this example we can't use something like this for compatibility purpose
	33	* since this will fail:
	34	*
	35	* #define GET_SIZE(x) x->size;
	36	*
	37	* This is mostly use for the compatibility layer of lttng-tools. See
	38	* poll/epoll for a good example. Since x can be on the stack or allocated
	39	* memory using malloc(), we must use generic accessors for compat in order to
	40	* not use a function to access members and not the variable name.
	41	*/
	42	#define LTTNG_REF(x) ((typeof((x)) ) (x))
	43
	44	#ifdef NDEBUG
	45	/*
	46	* Force usage of the assertion condition to prevent unused variable warnings
	47	* when `assert()` are disabled by the `NDEBUG` definition.
	48	*/
	49	# define LTTNG_ASSERT(_cond) ((void) sizeof((void) (_cond), 0))
	50	#else
	51	# include <assert.h>
	52	# define LTTNG_ASSERT(_cond) assert(_cond)
	53	#endif
	54
	55	/*
	56	* Memory allocation zeroed
	57	*/
	58
	59	static inline
	60	void *zmalloc_internal(size_t size)
	61	{
	62	return calloc(1, size);
	63	}
	64
	65	template <typename MallocableType>
	66	struct can_malloc {
	67	/*
	68	* gcc versions before 5.0 lack some type traits defined in C++11.
	69	* Since in this instance we use the trait to prevent misuses
	70	* of malloc (and statically assert) and not to generate different
	71	* code based on this property, simply set value to true and allow
	72	* the code to compile. Anyone using a contemporary compiler will
	73	* catch the error.
	74	*/
	75	#if __GNUG__ && __GNUC__ < 5
	76	static constexpr bool value = true;
	77	#else
	78	static constexpr bool value = std::is_trivially_constructible<MallocableType>::value;
	79	#endif
	80	};
	81
	82	/*
	83	* Malloc and zero-initialize an object of type T, asserting that MallocableType can be
	84	* safely malloc-ed (is trivially constructible).
	85	*/
	86	template <typename MallocableType>
	87	MallocableType *zmalloc()
	88	{
	89	static_assert(can_malloc<MallocableType>::value, "type can be malloc'ed");
	90	return (MallocableType ) zmalloc_internal(sizeof(MallocableType)); / NOLINT sizeof
	91	potentially used on a
	92	pointer. */
	93	}
	94
	95	/*
	96	* Malloc and zero-initialize a buffer of size `size`, asserting that type AllocatedType
	97	* can be safely malloc-ed (is trivially constructible).
	98	*/
	99	template <typename AllocatedType>
	100	AllocatedType *zmalloc(size_t size)
	101	{
	102	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	103	LTTNG_ASSERT(size >= sizeof(AllocatedType));
	104	return (AllocatedType *) zmalloc_internal(size);
	105	}
	106
	107	/*
	108	* Malloc and zero-initialize an array of `nmemb` elements of type AllocatedType,
	109	* asserting that AllocatedType can be safely malloc-ed (is trivially constructible).
	110	*/
	111	template <typename AllocatedType>
	112	AllocatedType *calloc(size_t nmemb)
	113	{
	114	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	115	return (AllocatedType ) zmalloc_internal(nmemb sizeof(AllocatedType)); /* NOLINT sizeof
	116	potentially
	117	used on a
	118	pointer. */
	119	}
	120
	121	/*
	122	* Malloc an object of type AllocatedType, asserting that AllocatedType can be safely malloc-ed (is
	123	* trivially constructible).
	124	*/
	125	template <typename AllocatedType>
	126	AllocatedType *malloc()
	127	{
	128	static_assert(can_malloc<AllocatedType>::value, "type can be malloc'ed");
	129	return (AllocatedType *) malloc(sizeof(AllocatedType));
	130	}
	131
	132	/*
	133	* Malloc a buffer of size `size`, asserting that AllocatedType can be safely
	134	* malloc-ed (is trivially constructible).
	135	*/
	136	template<typename AllocatedType>
	137	AllocatedType *malloc(size_t size)
	138	{
	139	static_assert (can_malloc<AllocatedType>::value, "type can be malloc'ed");
	140	return (AllocatedType *) malloc(size);
	141	}
	142
	143	/*
	144	* Prevent using `free` on types that are non-POD.
	145	*
	146	* Declare a delete prototype of free if the parameter type is not safe to free
	147	* (non-POD).
	148	*
	149	* If the parameter is a pointer to void, we can't check if what is pointed
	150	* to is safe to free or not, as we don't know what is pointed to. Ideally,
	151	* all calls to free would be with a typed pointer, but there are too many
	152	* instances of passing a pointer to void to enforce that right now. So allow
	153	* pointers to void, these will not be checked.
	154	*/
	155
	156	template<typename FreedType>
	157	struct can_free
	158	{
	159	/*
	160	* gcc versions before 5.0 lack some type traits defined in C++11.
	161	* Since in this instance we use the trait to prevent misuses
	162	* of free (and statically assert) and not to generate different
	163	* code based on this property, simply set value to true and allow
	164	* the code to compile. Anyone using a contemporary compiler will
	165	* catch the error.
	166	*/
	167	#if __GNUG__ && __GNUC__ < 5
	168	static constexpr bool value = true;
	169	#else
	170	static constexpr bool value = std::is_trivially_destructible<FreedType>::value \|\|
	171	std::is_void<FreedType>::value;
	172	#endif
	173	};
	174
	175	template <typename FreedType, typename = typename std::enable_if<!can_free<FreedType>::value>::type>
	176	void free(FreedType *p) = delete;
	177
	178	template <typename InitializedType>
	179	struct can_memset {
	180	static constexpr bool value = std::is_pod<InitializedType>::value \|\|
	181	std::is_void<InitializedType>::value;
	182	};
	183
	184	template <typename InitializedType,
	185	typename = typename std::enable_if<!can_memset<InitializedType>::value>::type>
	186	void memset(InitializedType s, int c, size_t n) = delete;
	187
	188	template<typename T>
	189	struct can_memcpy
	190	{
	191	/*
	192	* gcc versions before 5.0 lack some type traits defined in C++11.
	193	* Since in this instance we use the trait to prevent misuses
	194	* of memcpy (and statically assert) and not to generate different
	195	* code based on this property, simply set value to true and allow
	196	* the code to compile. Anyone using a contemporary compiler will
	197	* catch the error.
	198	*/
	199	#if __GNUG__ && __GNUC__ < 5
	200	static constexpr bool value = true;
	201	#else
	202	static constexpr bool value = std::is_trivially_copyable<T>::value;
	203	#endif
	204	};
	205
	206	template <typename DestinationType,
	207	typename SourceType,
	208	typename = typename std::enable_if<!can_memcpy<DestinationType>::value>::type,
	209	typename = typename std::enable_if<!can_memcpy<SourceType>::value>::type>
	210	void memcpy(DestinationType d, const SourceType *s, size_t n) = delete;
	211
	212	template <typename MovedType>
	213	struct can_memmove {
	214	/*
	215	* gcc versions before 5.0 lack some type traits defined in C++11.
	216	* Since in this instance we use the trait to prevent misuses
	217	* of memmove (and statically assert) and not to generate different
	218	* code based on this property, simply set value to true and allow
	219	* the code to compile. Anyone using a contemporary compiler will
	220	* catch the error.
	221	*/
	222	#if __GNUG__ && __GNUC__ < 5
	223	static constexpr bool value = true;
	224	#else
	225	static constexpr bool value = std::is_trivially_copyable<MovedType>::value;
	226	#endif
	227	};
	228
	229	template <typename DestinationType,
	230	typename SourceType,
	231	typename = typename std::enable_if<!can_memmove<DestinationType>::value>::type,
	232	typename = typename std::enable_if<!can_memmove<SourceType>::value>::type>
	233	void memmove(DestinationType d, const SourceType *s, size_t n) = delete;
	234
	235	#ifndef ARRAY_SIZE
	236	#define ARRAY_SIZE(array) (sizeof(array) / (sizeof((array)[0])))
	237	#endif
	238
	239	#ifndef LTTNG_PACKED
	240	#define LTTNG_PACKED __attribute__((__packed__))
	241	#endif
	242
	243	#ifndef LTTNG_NO_SANITIZE_ADDRESS
	244	#if defined(__clang__) \|\| defined (__GNUC__)
	245	#define LTTNG_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
	246	#else
	247	#define LTTNG_NO_SANITIZE_ADDRESS
	248	#endif
	249	#endif
	250
	251	#define member_sizeof(type, field) sizeof(((type *) 0)->field)
	252
	253	#define ASSERT_LOCKED(lock) LTTNG_ASSERT(pthread_mutex_trylock(&(lock)))
	254	#define ASSERT_RCU_READ_LOCKED() LTTNG_ASSERT(rcu_read_ongoing())
	255	#define ASSERT_RCU_READ_UNLOCKED() LTTNG_ASSERT(!rcu_read_ongoing())
	256
	257	/* Attribute suitable to tag functions as having printf()-like arguments. */
	258	#define ATTR_FORMAT_PRINTF(_string_index, _first_to_check) \
	259	__attribute__((format(printf, _string_index, _first_to_check)))
	260
	261	/* Attribute suitable to tag functions as having strftime()-like arguments. */
	262	#define ATTR_FORMAT_STRFTIME(_string_index) \
	263	__attribute__((format(strftime, _string_index, 0)))
	264
	265	/* Macros used to ignore specific compiler diagnostics. */
	266
	267	#define DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
	268	#define DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
	269
	270	#if defined(__clang__)
	271	/* Clang */
	272	# define DIAGNOSTIC_IGNORE_SUGGEST_ATTRIBUTE_FORMAT
	273	# define DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL \
	274	_Pragma("GCC diagnostic ignored \"-Wformat-nonliteral\"")
	275	# define DIAGNOSTIC_IGNORE_LOGICAL_OP
	276	# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES
	277	# define DIAGNOSTIC_IGNORE_INVALID_OFFSETOF
	278	_Pragma("GCC diagnostic ignored \"-Winvalid-offsetof\"")
	279	#else
	280	/* GCC */
	281	# define DIAGNOSTIC_IGNORE_SUGGEST_ATTRIBUTE_FORMAT \
	282	_Pragma("GCC diagnostic ignored \"-Wsuggest-attribute=format\"")
	283	# define DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL \
	284	_Pragma("GCC diagnostic ignored \"-Wformat-nonliteral\"")
	285	# define DIAGNOSTIC_IGNORE_LOGICAL_OP \
	286	_Pragma("GCC diagnostic ignored \"-Wlogical-op\"")
	287	#if __GNUG__ && __GNUC__ >= 7
	288	# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES \
	289	_Pragma("GCC diagnostic ignored \"-Wduplicated-branches\"")
	290	#else
	291	# define DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES
	292	#endif /* __GNUG__ && __GNUC__ >= 7 */
	293	# define DIAGNOSTIC_IGNORE_INVALID_OFFSETOF \
	294	_Pragma("GCC diagnostic ignored \"-Winvalid-offsetof\"")
	295	#endif
	296
	297	/* Used to make specific C++ functions to C code. */
	298	#ifdef __cplusplus
	299	#define C_LINKAGE extern "C"
	300	#else
	301	#define C_LINKAGE
	302	#endif
	303
	304	/*
	305	* lttng_strncpy returns 0 on success, or nonzero on failure.
	306	* It checks that the @src string fits into @dst_len before performing
	307	* the copy. On failure, no copy has been performed.
	308	*
	309	* Assumes that 'src' is null-terminated.
	310	*
	311	* dst_len includes the string's trailing NULL.
	312	*/
	313	static inline
	314	int lttng_strncpy(char dst, const char src, size_t dst_len)
	315	{
	316	if (strlen(src) >= dst_len) {
	317	/* Fail since copying would result in truncation. */
	318	return -1;
	319	}
	320	strcpy(dst, src);
	321	return 0;
	322	}
	323
	324	namespace lttng {
	325	namespace utils {
	326	template <class ParentType, class MemberType>
	327	ParentType container_of(const MemberType member, const MemberType ParentType::*ptr_to_member)
	328	{
	329	const ParentType *dummy_parent = nullptr;
	330	auto offset_of_member = reinterpret_cast<const char >(&(dummy_parent->*ptr_to_member));
	331	auto address_of_parent = reinterpret_cast<const char *>(member) - offset_of_member;
	332
	333	return reinterpret_cast<ParentType *>(address_of_parent);
	334	}
	335	} /* namespace utils */
	336	} /* namespace lttng */
	337
	338	#endif /* _MACROS_H */