[vlc-devel] [PATCH 1/2] Add helpers for unsigned integer overflow

[Romain Vimont]

Le dimanche 12 novembre 2017 à 11:27 +0200, Rémi Denis-Courmont a écrit :
> ---
>  include/vlc_common.h | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 114 insertions(+)
> 
> diff --git a/include/vlc_common.h b/include/vlc_common.h
> index ed5ff77730..e3d7086ff7 100644
> --- a/include/vlc_common.h
> +++ b/include/vlc_common.h
> @@ -661,6 +661,120 @@ static inline uint64_t (bswap64)(uint64_t x)
>  #endif
>  }
>  
> +/* Integer overflow */
> +static inline bool uadd_overflow(unsigned a, unsigned b, unsigned *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_uadd_overflow(a, b, res);
> +#else
> +     *res = a + b;
> +     return (a + b) > a;

(a + b) < a

> +#endif
> +}
> +
> +static inline bool uaddl_overflow(unsigned long a, unsigned long b,
> +                                  unsigned long *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_uaddl_overflow(a, b, res);
> +#else
> +     *res = a + b;
> +     return (a + b) > a;

(a + b) < a

> +#endif
> +}
> +
> +static inline bool uaddll_overflow(unsigned long long a, unsigned long long b,
> +                                   unsigned long long *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_uaddll_overflow(a, b, res);
> +#else
> +     *res = a + b;
> +     return (a + b) > a;

(a + b) < a

> +#endif
> +}
> +
> +#ifndef __cplusplus
> +# define add_overflow(a,b,r) \
> +    _Generic(*(r), \
> +        unsigned: uadd_overflow(a, b, (unsigned *)(r)), \
> +        unsigned long: uaddl_overflow(a, b, (unsigned long *)(r)), \
> +        unsigned long long: uaddll_overflow(a, b, (unsigned long long *)(r)))
> +#else
> +static inline bool add_overflow(unsigned a, unsigned b, unsigned *res)
> +{
> +    return uadd_overflow(a, b, res);
> +}
> +
> +static inline bool add_overflow(unsigned long a, unsigned long b,
> +                                unsigned long *res)
> +{
> +    return uaddl_overflow(a, b, res);
> +}
> +
> +static inline bool add_overflow(unsigned long long a, unsigned long long b,
> +                                unsigned long long *res)
> +{
> +    return uaddll_overflow(a, b, res);
> +}
> +#endif
> +
> +static inline bool umul_overflow(unsigned a, unsigned b, unsigned *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_umul_overflow(a, b, res);
> +#else
> +     *res = a * b;
> +     return b > 0 && a > (UINT_MAX / b);
> +#endif
> +}
> +
> +static inline bool umull_overflow(unsigned long a, unsigned long b,
> +                                  unsigned long *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_umull_overflow(a, b, res);
> +#else
> +     *res = a * b;
> +     return b > 0 && a > (ULONG_MAX / b);
> +#endif
> +}
> +
> +static inline bool umulll_overflow(unsigned long long a, unsigned long long b,
> +                                   unsigned long long *res)
> +{
> +#ifdef __GNUC__
> +     return __builtin_umulll_overflow(a, b, res);
> +#else
> +     *res = a * b;
> +     return b > 0 && a > (ULLONG_MAX / b);
> +#endif
> +}
> +
> +#ifndef __cplusplus
> +#define mul_overflow(a,b,r) \
> +    _Generic(*(r), \
> +        unsigned: umul_overflow(a, b, (unsigned *)(r)), \
> +        unsigned long: umull_overflow(a, b, (unsigned long *)(r)), \
> +        unsigned long long: umulll_overflow(a, b, (unsigned long long *)(r)))
> +#else
> +static inline bool mul_overflow(unsigned a, unsigned b, unsigned *res)
> +{
> +    return umul_overflow(a, b, res);
> +}
> +
> +static inline bool mul_overflow(unsigned long a, unsigned long b,
> +                                unsigned long *res)
> +{
> +    return umull_overflow(a, b, res);
> +}
> +
> +static inline bool mul_overflow(unsigned long long a, unsigned long long b,
> +                                unsigned long long *res)
> +{
> +    return umulll_overflow(a, b, res);
> +}
> +#endif
>  
>  /* Free and set set the variable to NULL */
>  #define FREENULL(a) do { free( a ); a = NULL; } while(0)
> -- 
> 2.15.0
> 
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