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c396aca2b7
When computing "0 - INT64_MIN", most platforms would report an overflow error, which is correct. However, platforms without integer overflow builtins or 128-bit integers would fail to spot the overflow, and incorrectly return INT64_MIN. Back-patch to all supported branches. Patch be me. Thanks to Jian He for initial investigation, and Laurenz Albe and Tom Lane for review. Discussion: https://postgr.es/m/CAEZATCUNK-AZSD0jVdgkk0N%3DNcAXBWeAEX-QU9AnJPensikmdQ%40mail.gmail.com
442 lines
9.7 KiB
C
442 lines
9.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* int.h
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* Routines to perform integer math, while checking for overflows.
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*
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* The routines in this file are intended to be well defined C, without
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* relying on compiler flags like -fwrapv.
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*
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* To reduce the overhead of these routines try to use compiler intrinsics
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* where available. That's not that important for the 16, 32 bit cases, but
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* the 64 bit cases can be considerably faster with intrinsics. In case no
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* intrinsics are available 128 bit math is used where available.
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*
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* Copyright (c) 2017-2023, PostgreSQL Global Development Group
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*
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* src/include/common/int.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef COMMON_INT_H
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#define COMMON_INT_H
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/*---------
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* The following guidelines apply to all the routines:
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* - If a + b overflows, return true, otherwise store the result of a + b
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* into *result. The content of *result is implementation defined in case of
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* overflow.
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* - If a - b overflows, return true, otherwise store the result of a - b
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* into *result. The content of *result is implementation defined in case of
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* overflow.
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* - If a * b overflows, return true, otherwise store the result of a * b
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* into *result. The content of *result is implementation defined in case of
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* overflow.
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*---------
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*/
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/*------------------------------------------------------------------------
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* Overflow routines for signed integers
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*------------------------------------------------------------------------
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*/
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/*
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* INT16
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*/
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static inline bool
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pg_add_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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int32 res = (int32) a + (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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static inline bool
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pg_sub_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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int32 res = (int32) a - (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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static inline bool
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pg_mul_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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int32 res = (int32) a * (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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/*
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* INT32
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*/
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static inline bool
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pg_add_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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int64 res = (int64) a + (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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static inline bool
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pg_sub_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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int64 res = (int64) a - (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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static inline bool
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pg_mul_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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int64 res = (int64) a * (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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/*
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* INT64
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*/
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static inline bool
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pg_add_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a + (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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if ((a > 0 && b > 0 && a > PG_INT64_MAX - b) ||
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(a < 0 && b < 0 && a < PG_INT64_MIN - b))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a + b;
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return false;
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#endif
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}
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static inline bool
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pg_sub_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a - (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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/*
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* Note: overflow is also possible when a == 0 and b < 0 (specifically,
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* when b == PG_INT64_MIN).
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*/
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if ((a < 0 && b > 0 && a < PG_INT64_MIN + b) ||
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(a >= 0 && b < 0 && a > PG_INT64_MAX + b))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a - b;
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return false;
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#endif
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}
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static inline bool
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pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a * (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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/*
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* Overflow can only happen if at least one value is outside the range
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* sqrt(min)..sqrt(max) so check that first as the division can be quite a
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* bit more expensive than the multiplication.
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*
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* Multiplying by 0 or 1 can't overflow of course and checking for 0
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* separately avoids any risk of dividing by 0. Be careful about dividing
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* INT_MIN by -1 also, note reversing the a and b to ensure we're always
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* dividing it by a positive value.
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*
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*/
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if ((a > PG_INT32_MAX || a < PG_INT32_MIN ||
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b > PG_INT32_MAX || b < PG_INT32_MIN) &&
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a != 0 && a != 1 && b != 0 && b != 1 &&
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((a > 0 && b > 0 && a > PG_INT64_MAX / b) ||
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(a > 0 && b < 0 && b < PG_INT64_MIN / a) ||
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(a < 0 && b > 0 && a < PG_INT64_MIN / b) ||
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(a < 0 && b < 0 && a < PG_INT64_MAX / b)))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a * b;
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return false;
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#endif
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}
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/*------------------------------------------------------------------------
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* Overflow routines for unsigned integers
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*------------------------------------------------------------------------
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*/
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/*
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* UINT16
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*/
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static inline bool
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pg_add_u16_overflow(uint16 a, uint16 b, uint16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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uint16 res = a + b;
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if (res < a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = res;
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return false;
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#endif
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}
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static inline bool
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pg_sub_u16_overflow(uint16 a, uint16 b, uint16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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if (b > a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a - b;
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return false;
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#endif
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}
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static inline bool
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pg_mul_u16_overflow(uint16 a, uint16 b, uint16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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uint32 res = (uint32) a * (uint32) b;
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if (res > PG_UINT16_MAX)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (uint16) res;
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return false;
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#endif
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}
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/*
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* INT32
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*/
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static inline bool
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pg_add_u32_overflow(uint32 a, uint32 b, uint32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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uint32 res = a + b;
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if (res < a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = res;
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return false;
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#endif
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}
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static inline bool
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pg_sub_u32_overflow(uint32 a, uint32 b, uint32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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if (b > a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a - b;
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return false;
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#endif
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}
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static inline bool
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pg_mul_u32_overflow(uint32 a, uint32 b, uint32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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uint64 res = (uint64) a * (uint64) b;
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if (res > PG_UINT32_MAX)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (uint32) res;
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return false;
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#endif
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}
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/*
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* UINT64
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*/
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static inline bool
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pg_add_u64_overflow(uint64 a, uint64 b, uint64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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uint64 res = a + b;
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if (res < a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = res;
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return false;
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#endif
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}
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static inline bool
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pg_sub_u64_overflow(uint64 a, uint64 b, uint64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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if (b > a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a - b;
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return false;
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#endif
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}
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static inline bool
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pg_mul_u64_overflow(uint64 a, uint64 b, uint64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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uint128 res = (uint128) a * (uint128) b;
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if (res > PG_UINT64_MAX)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (uint64) res;
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return false;
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#else
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uint64 res = a * b;
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if (a != 0 && b != res / a)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = res;
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return false;
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#endif
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}
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#endif /* COMMON_INT_H */
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