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Disable unsigned integer sanitizer for basic_string::replace(). Patch from tomcherry@google.com

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basic_string::replace() has the below line

__sz += __n2 - __n1;

which fails overflow checks if __n1 > __n2, as the negative result
from the subtraction then overflows the original __sz when added to
it.

This behavior is valid as unsigned integer overflow is defined to wrap
around the maximum value and that produces the correct final value for
__sz.  Therefore, we disable this check on this function.

llvm-svn: 297355
This commit is contained in:
Eric Fiselier 2017-03-09 01:54:13 +00:00
parent 9a3fd87523
commit 84a2dadcee
1 changed files with 4 additions and 0 deletions
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4
libcxx/include/string
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@ -2560,6 +2560,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, size_typ
template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2)
_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
{
_LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::replace received nullptr");
size_type __sz = size();
@ -2599,6 +2600,8 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __
}
traits_type::move(__p + __pos, __s, __n2);
__finish:
// __sz += __n2 - __n1; in this and the below function below can cause unsigned integer overflow,
// but this is a safe operation, so we disable the check.
__sz += __n2 - __n1;
__set_size(__sz);
__invalidate_iterators_past(__sz);
@ -2612,6 +2615,7 @@ __finish:
template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>&
basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, size_type __n2, value_type __c)
_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
{
size_type __sz = size();
if (__pos > __sz)