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