src/common/macros.h

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #ifndef _MACROS_H
  20 #define _MACROS_H
  21
  22 #include <stdlib.h>
  23
  24 /*
  25  * Takes a pointer x and transform it so we can use it to access members
  26  * without a function call. Here an example:
  27  *
  28  *    #define GET_SIZE(x) LTTNG_REF(x)->size
  29  *
  30  *    struct { int size; } s;
  31  *
  32  *    printf("size : %d\n", GET_SIZE(&s));
  33  *
  34  * For this example we can't use something like this for compatibility purpose
  35  * since this will fail:
  36  *
  37  *    #define GET_SIZE(x) x->size;
  38  *
  39  * This is mostly use for the compatibility layer of lttng-tools. See
  40  * poll/epoll for a good example. Since x can be on the stack or allocated
  41  * memory using malloc(), we must use generic accessors for compat in order to
  42  * *not* use a function to access members and not the variable name.
  43  */
  44 #define LTTNG_REF(x) ((typeof(*x) *)(x))
  45
  46 /*
  47  * Memory allocation zeroed
  48  */
  49 #define zmalloc(x) calloc(1, x)
  50
  51 #ifndef ARRAY_SIZE
  52 #define ARRAY_SIZE(array)   (sizeof(array) / (sizeof((array)[0])))
  53 #endif
  54
  55 #ifndef max
  56 #define max(a, b) ((a) > (b) ? (a) : (b))
  57 #endif
  58
  59 #ifndef max_t
  60 #define max_t(type, a, b)       ((type) max(a, b))
  61 #endif
  62
  63 #ifndef min
  64 #define min(a, b) ((a) < (b) ? (a) : (b))
  65 #endif
  66
  67 #ifndef LTTNG_PACKED
  68 #define LTTNG_PACKED __attribute__((__packed__))
  69 #endif
  70
  71 #ifndef LTTNG_HIDDEN
  72 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
  73 #endif
  74
  75 #endif /* _MACROS_H */