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libstdc++: Fix memchr path in std::ranges::find for non-common range [PR115799]

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The memchr optimization introduced in r15-1857 needs to advance the
start iterator instead of returning the sentinel.

libstdc++-v3/ChangeLog:

	PR libstdc++/115799
	* include/bits/ranges_util.h (__find_fn): Return iterator
	instead of sentinel.
	* testsuite/25_algorithms/find/constrained.cc: Check non-common
	contiguous sized range of char.
This commit is contained in:
Jonathan Wakely 2024-07-05 18:58:00 +01:00 • committed by Jonathan Wakely
parent e78c5d0ae4
commit 762ee55d36
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2 changed files with 19 additions and 10 deletions
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19
libstdc++-v3/include/bits/ranges_util.h
View file

@ -501,17 +501,16 @@ namespace ranges
if constexpr (contiguous_iterator<_Iter>)
if (!is_constant_evaluated())
{
if (static_cast<iter_value_t<_Iter>>(__value) != __value)
return __last;
using _Vt = iter_value_t<_Iter>;
auto __n = __last - __first;
if (__n > 0)
{
const int __ival = static_cast<int>(__value);
const void* __p0 = std::to_address(__first);
if (auto __p1 = __builtin_memchr(__p0, __ival, __n))
__n = (const char*)__p1 - (const char*)__p0;
}
if (static_cast<_Vt>(__value) == __value) [[likely]]
if (__n > 0)
{
const int __ival = static_cast<int>(__value);
const void* __p0 = std::to_address(__first);
if (auto __p1 = __builtin_memchr(__p0, __ival, __n))
__n = (const char*)__p1 - (const char*)__p0;
}
return __first + __n;
}

10
libstdc++-v3/testsuite/25_algorithms/find/constrained.cc
View file

@ -66,9 +66,19 @@ test02()
static_assert(ranges::find(y, 5, &Y::j) == y+3);
}
void
test_pr115799()
{
const char str[3] = { 'a', 'b', 'c' };
__gnu_test::test_contiguous_sized_range<const char> r(str);
VERIFY(std::ranges::find(r, 'a') == std::ranges::begin(r));
VERIFY(std::ranges::find(r, 'a'+255) == std::ranges::end(r));
}
int
main()
{
test01();
test02();
test_pr115799();
}