27 #define SIZECALC_H
  28 
  29 /*
  30  * A machinery for safe calculation of sizes used when allocating memory.
  31  *
  32  * All size checks are performed against the SIZE_MAX (the maximum value for
  33  * size_t). All numerical arguments as well as the result of calculation must
  34  * be non-negative integers less than or equal to SIZE_MAX, otherwise the
  35  * calculated size is considered unsafe.
  36  *
  37  * If the SIZECALC_ALLOC_THROWING_BAD_ALLOC macro is defined, then _ALLOC_
  38  * helper macros throw the std::bad_alloc instead of returning NULL.
  39  */
  40 
  41 #include <stdint.h> /* SIZE_MAX for C99+ */
  42 /* http://stackoverflow.com/questions/3472311/what-is-a-portable-method-to-find-the-maximum-value-of-size-t */
  43 #ifndef SIZE_MAX
  44 #define SIZE_MAX ((size_t)-1)
  45 #endif
  46 
  47 #define IS_SAFE_SIZE_T(x) ((x) >= 0 && (unsigned long long)(x) <= SIZE_MAX)
  48 
  49 #define IS_SAFE_SIZE_MUL(m, n) \
  50     (IS_SAFE_SIZE_T(m) && IS_SAFE_SIZE_T(n) && ((m) == 0 || (n) == 0 || (size_t)(n) <= (SIZE_MAX / (size_t)(m))))
  51 
  52 #define IS_SAFE_SIZE_ADD(a, b) \
  53     (IS_SAFE_SIZE_T(a) && IS_SAFE_SIZE_T(b) && (size_t)(b) <= (SIZE_MAX - (size_t)(a)))
  54 
  55 
  56 
  57 /* Helper macros */
  58 
  59 #ifdef SIZECALC_ALLOC_THROWING_BAD_ALLOC
  60 #define FAILURE_RESULT throw std::bad_alloc()
  61 #else
  62 #define FAILURE_RESULT NULL
  63 #endif
  64 
  65 /*
  66  * A helper macro to safely allocate an array of size m*n.
  67  * Example usage:

  27 #define SIZECALC_H
  28 
  29 /*
  30  * A machinery for safe calculation of sizes used when allocating memory.
  31  *
  32  * All size checks are performed against the SIZE_MAX (the maximum value for
  33  * size_t). All numerical arguments as well as the result of calculation must
  34  * be non-negative integers less than or equal to SIZE_MAX, otherwise the
  35  * calculated size is considered unsafe.
  36  *
  37  * If the SIZECALC_ALLOC_THROWING_BAD_ALLOC macro is defined, then _ALLOC_
  38  * helper macros throw the std::bad_alloc instead of returning NULL.
  39  */
  40 
  41 #include <stdint.h> /* SIZE_MAX for C99+ */
  42 /* http://stackoverflow.com/questions/3472311/what-is-a-portable-method-to-find-the-maximum-value-of-size-t */
  43 #ifndef SIZE_MAX
  44 #define SIZE_MAX ((size_t)-1)
  45 #endif
  46 
  47 #define IS_SAFE_SIZE_T(x) (((x) + 1) > 0 && (unsigned long long)(x) - 1u < SIZE_MAX)
  48 
  49 #define IS_SAFE_SIZE_MUL(m, n) \
  50     (IS_SAFE_SIZE_T(m) && IS_SAFE_SIZE_T(n) && ((m) == 0 || (n) == 0 || (size_t)(n) <= (SIZE_MAX / (size_t)(m))))
  51 
  52 #define IS_SAFE_SIZE_ADD(a, b) \
  53     (IS_SAFE_SIZE_T(a) && IS_SAFE_SIZE_T(b) && (size_t)(b) <= (SIZE_MAX - (size_t)(a)))
  54 
  55 
  56 
  57 /* Helper macros */
  58 
  59 #ifdef SIZECALC_ALLOC_THROWING_BAD_ALLOC
  60 #define FAILURE_RESULT throw std::bad_alloc()
  61 #else
  62 #define FAILURE_RESULT NULL
  63 #endif
  64 
  65 /*
  66  * A helper macro to safely allocate an array of size m*n.
  67  * Example usage: