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7474cad4ad
The `ISC_OVERFLOW_XXX()` macros are usually wrappers around `__builtin_xxx_overflow()`, with alternative implementations for compilers that lack the builtins. Replace the overflow checks in `isc/time.c` with the new macros.
95 lines
3.4 KiB
C
95 lines
3.4 KiB
C
/*
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* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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*
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* SPDX-License-Identifier: MPL-2.0
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, you can obtain one at https://mozilla.org/MPL/2.0/.
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*
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* See the COPYRIGHT file distributed with this work for additional
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* information regarding copyright ownership.
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*/
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#pragma once
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#include <isc/util.h>
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/*
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* It is awkward to support signed numbers as well, so keep it simple
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* (with a safety check).
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*/
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#define ISC_OVERFLOW_IS_UNSIGNED(a) \
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({ \
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STATIC_ASSERT((typeof(a))-1 > 0, \
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"overflow checks require unsigned types"); \
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(a); \
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})
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#define ISC_OVERFLOW_UINT_MAX(a) ISC_OVERFLOW_IS_UNSIGNED((typeof(a))-1)
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#define ISC_OVERFLOW_UINT_MIN(a) ISC_OVERFLOW_IS_UNSIGNED(0)
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/*
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* Return true on overflow, e.g.
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*
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* bool overflow = ISC_OVERFLOW_MUL(count, sizeof(array[0]), &bytes);
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* INSIST(!overflow);
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*/
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#if HAVE_BUILTIN_MUL_OVERFLOW
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#define ISC_OVERFLOW_MUL(a, b, cp) __builtin_mul_overflow(a, b, cp)
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#else
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#define ISC_OVERFLOW_MUL(a, b, cp) \
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((ISC_OVERFLOW_UINT_MAX(a) / (b) > (a)) ? (*(cp) = (a) * (b), false) \
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: true)
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#endif
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#if HAVE_BUILTIN_ADD_OVERFLOW
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#define ISC_OVERFLOW_ADD(a, b, cp) __builtin_add_overflow(a, b, cp)
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#else
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#define ISC_OVERFLOW_ADD(a, b, cp) \
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((ISC_OVERFLOW_UINT_MAX(a) - (b) > (a)) ? (*(cp) = (a) + (b), false) \
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: true)
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#endif
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#if HAVE_BUILTIN_SUB_OVERFLOW
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#define ISC_OVERFLOW_SUB(a, b, cp) __builtin_sub_overflow(a, b, cp)
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#else
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#define ISC_OVERFLOW_SUB(a, b, cp) \
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((ISC_OVERFLOW_UINT_MIN(a) + (b) < (a)) ? (*(cp) = (a) - (b), false) \
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: true)
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#endif
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#define ISC_CHECKED_MUL(a, b) \
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({ \
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typeof(a) _c; \
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bool _overflow = ISC_OVERFLOW_MUL(a, b, &_c); \
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INSIST(!_overflow); \
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_c; \
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})
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#define ISC_CHECKED_ADD(a, b) \
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({ \
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typeof(a) _c; \
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bool _overflow = ISC_OVERFLOW_ADD(a, b, &_c); \
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INSIST(!_overflow); \
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_c; \
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})
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#define ISC_CHECKED_SUB(a, b) \
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({ \
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typeof(a) _c; \
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bool _overflow = ISC_OVERFLOW_SUB(a, b, cp); \
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INSIST(!_overflow); \
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_c; \
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})
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#define ISC_CHECKED_MUL_ADD(a, b, c) \
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({ \
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size_t _d; \
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bool _overflow = ISC_OVERFLOW_MUL(a, b, &_d) || \
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ISC_OVERFLOW_ADD(_d, c, &_d); \
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INSIST(!_overflow); \
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_d; \
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})
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