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[libc++] span: Guard against overflow in span::subspan
The calculation _Offset + _Count <= size() may overflow, so use _Count <= size() - _Offset instead. Note that this is safe due to the previous constraint that _Offset <= size(). Patch by Michael Schellenberger Costa. Differential Revision: https://reviews.llvm.org/D71998
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libcxx/test/std/containers/views/span.sub/subspan.fail.cpp
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// -*- C++ -*- | ||
//===------------------------------ span ---------------------------------===// | ||
// | ||
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
// See https://llvm.org/LICENSE.txt for license information. | ||
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
// | ||
//===---------------------------------------------------------------------===// | ||
// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17 | ||
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// <span> | ||
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// template<size_t Offset, size_t Count = dynamic_extent> | ||
// constexpr span<element_type, see below> subspan() const; | ||
// | ||
// constexpr span<element_type, dynamic_extent> subspan( | ||
// size_type offset, size_type count = dynamic_extent) const; | ||
// | ||
// Requires: offset <= size() && | ||
// (count == dynamic_extent || count <= size() - offset) | ||
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#include <span> | ||
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#include "test_macros.h" | ||
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constexpr int carr[] = {1, 2, 3, 4}; | ||
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int main(int, char**) { | ||
std::span<const int, 4> sp(carr); | ||
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// Offset too large templatized | ||
{ | ||
[[maybe_unused]] auto s1 = sp.subspan<5>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Offset out of range in span::subspan()"}} | ||
} | ||
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// Count too large templatized | ||
{ | ||
[[maybe_unused]] auto s1 = sp.subspan<0, 5>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Offset + count out of range in span::subspan()"}} | ||
} | ||
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// Offset + Count too large templatized | ||
{ | ||
[[maybe_unused]] auto s1 = sp.subspan<2, 3>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Offset + count out of range in span::subspan()"}} | ||
} | ||
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// Offset + Count overflow templatized | ||
{ | ||
[[maybe_unused]] auto s1 = sp.subspan<3, std::size_t(-2)>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Offset + count out of range in span::subspan()"}}, expected-error-re@span:* {{array is too large{{(.* elements)}}}} | ||
} | ||
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return 0; | ||
} |