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