include/lttng/ust-compiler.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  * Copyright (C) 2011-2012 Paul Woegerer <paul_woegerer@mentor.com>
   6  */
   7
   8 #ifndef _LTTNG_UST_COMPILER_H
   9 #define _LTTNG_UST_COMPILER_H
  10
  11 #include <assert.h>
  12
  13 #define lttng_ust_notrace __attribute__((no_instrument_function))
  14
  15 /*
  16  * Clang supports the no_sanitize variable attribute on global variables.
  17  * GCC only supports the no_sanitize_address function attribute, which is
  18  * not what we need.
  19  */
  20 #if defined(__clang__)
  21 # if __has_feature(address_sanitizer)
  22 #  define __lttng_ust_variable_attribute_no_sanitize_address \
  23         __attribute__((no_sanitize("address")))
  24 # else
  25 #  define __lttng_ust_variable_attribute_no_sanitize_address
  26 # endif
  27 #else
  28 #  define __lttng_ust_variable_attribute_no_sanitize_address
  29 #endif
  30
  31 /*
  32  * g++ 4.8 and prior do not support C99 compound literals. Therefore,
  33  * force allocating those on the heap with these C++ compilers.
  34  */
  35 #if defined (__cplusplus) && !defined (__clang__) && defined (__GNUC__) && \
  36         ((__GNUC__ < 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ <= 8)))
  37 # ifndef LTTNG_UST_ALLOCATE_COMPOUND_LITERAL_ON_HEAP
  38 #  define LTTNG_UST_ALLOCATE_COMPOUND_LITERAL_ON_HEAP
  39 # endif
  40 #endif
  41
  42 /*
  43  * Compound literals with static storage are needed by LTTng.
  44  * Compound literals are part of the C99 and C11 standards, but not
  45  * part of the C++ standards. However, those are supported by both g++ and
  46  * clang. In order to be strictly C++11 compliant, defining
  47  * LTTNG_UST_ALLOCATE_COMPOUND_LITERAL_ON_HEAP before including this header
  48  * allocates those on the heap in C++.
  49  *
  50  * Example use:
  51  * static struct mystruct *var = LTTNG_UST_COMPOUND_LITERAL(struct mystruct, { 1, 2, 3 });
  52  */
  53 #if defined (__cplusplus) && defined (LTTNG_UST_ALLOCATE_COMPOUND_LITERAL_ON_HEAP)
  54 #define LTTNG_UST_COMPOUND_LITERAL(type, ...)   new (type) __VA_ARGS__
  55 #else
  56 #define LTTNG_UST_COMPOUND_LITERAL(type, ...)   (type[]) { __VA_ARGS__ }
  57 #endif
  58
  59 /*
  60  * Compile time assertion.
  61  * - predicate: boolean expression to evaluate,
  62  * - msg: string to print to the user on failure when `static_assert()` is
  63  *   supported,
  64  * - c_identifier_msg: message to be included in the typedef to emulate a
  65  *   static assertion. This parameter must be a valid C identifier as it will
  66  *   be used as a typedef name.
  67  */
  68 #ifdef __cplusplus
  69 #define lttng_ust_static_assert(predicate, msg, c_identifier_msg)  \
  70         static_assert(predicate, msg)
  71 #elif __STDC_VERSION__ >= 201112L
  72 #define lttng_ust_static_assert(predicate, msg, c_identifier_msg)  \
  73         _Static_assert(predicate, msg)
  74 #else
  75 /*
  76  * Evaluates the predicate and emit a compilation error on failure.
  77  *
  78  * If the predicate evaluates to true, this macro emits a typedef of an array
  79  * of size 0.
  80  *
  81  * If the predicate evaluates to false, this macro emits a typedef of an array
  82  * of negative size which is invalid in C and forces a compiler error. The msg
  83  * parameter is used in the tentative typedef so it is printed to the user.
  84  */
  85 #define lttng_ust_static_assert(predicate, msg, c_identifier_msg)  \
  86     typedef char lttng_ust_static_assert_##c_identifier_msg[2*!!(predicate)-1]
  87 #endif
  88
  89 #endif /* _LTTNG_UST_COMPILER_H */