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[libc++] Fix wraparound issue with -fsanitize=integer in string operator>> #106263

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Merged
merged 3 commits into from
Aug 29, 2024
Merged

[libc++] Fix wraparound issue with -fsanitize=integer in string operator>> #106263

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8237152
[libc++] Fix wraparound issue with -fsanitize=integer in string opera…
ldionne Aug 27, 2024
2e12c32
Accept smaller size_types than streamsizes
ldionne Aug 27, 2024
c31b0fb
Review comments, take two
ldionne Aug 28, 2024
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4 changes: 1 addition & 3 deletions libcxx/include/__type_traits/make_unsigned.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,12 +86,10 @@ template <class _Tp>
using make_unsigned_t = __make_unsigned_t<_Tp>;
#endif

#ifndef _LIBCPP_CXX03_LANG
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr __make_unsigned_t<_Tp> __to_unsigned_like(_Tp __x) noexcept {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __make_unsigned_t<_Tp> __to_unsigned_like(_Tp __x) _NOEXCEPT {
return static_cast<__make_unsigned_t<_Tp> >(__x);
}
#endif

template <class _Tp, class _Up>
using __copy_unsigned_t = __conditional_t<is_unsigned<_Tp>::value, __make_unsigned_t<_Up>, _Up>;
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18 changes: 12 additions & 6 deletions libcxx/include/istream
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Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,7 @@ template <class Stream, class T>
#include <__type_traits/conjunction.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_base_of.h>
#include <__type_traits/make_unsigned.h>
#include <__utility/declval.h>
#include <__utility/forward.h>
#include <bitset>
Expand Down Expand Up @@ -1211,12 +1212,17 @@ operator>>(basic_istream<_CharT, _Traits>& __is, basic_string<_CharT, _Traits, _
try {
#endif
__str.clear();
streamsize __n = __is.width();
if (__n <= 0)
__n = __str.max_size();
if (__n <= 0)
__n = numeric_limits<streamsize>::max();
streamsize __c = 0;
using _Size = typename basic_string<_CharT, _Traits, _Allocator>::size_type;
streamsize const __width = __is.width();
_Size const __max_size = __str.max_size();
_Size __n;
if (__width <= 0) {
__n = __max_size;
} else {
__n = std::__to_unsigned_like(__width) < __max_size ? static_cast<_Size>(__width) : __max_size;
}

_Size __c = 0;
const ctype<_CharT>& __ct = std::use_facet<ctype<_CharT> >(__is.getloc());
while (__c < __n) {
typename _Traits::int_type __i = __is.rdbuf()->sgetc();
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