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libstdc++: Fix some algos for 16-bit size_t [PR108221]

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Some standard algorithms fail to compile when size_t or ptrdiff_t is
narrower than int. The __lg helper function is ambiguous if ptrdiff_t is
short or __int20, so replace it with a function template that works for
those types as well as signed/unsigned int/long/long long. The helpers
for stable_sort perform arithmetic on size values and assume the types
won't change, which isn't true if the type promotes to int.

libstdc++-v3/ChangeLog:

	PR libstdc++/108221
	* include/bits/stl_algobase.h (__lg): Replace six overloads with
	a single function template for all integer types.
	* include/bits/stl_algo.h (__merge_adaptive_resize): Cast
	arithmetic results back to _Distance.
This commit is contained in:
Jonathan Wakely 2023-01-09 10:45:31 +00:00
parent b39f4333d1
commit 769fae76df
2 changed files with 26 additions and 26 deletions
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5
libstdc++-v3/include/bits/stl_algo.h
View file

@ -2458,13 +2458,14 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
_BidirectionalIterator __new_middle
= std::__rotate_adaptive(__first_cut, __middle, __second_cut,
__len1 - __len11, __len22,
_Distance(__len1 - __len11), __len22,
__buffer, __buffer_size);
std::__merge_adaptive_resize(__first, __first_cut, __new_middle,
__len11, __len22,
__buffer, __buffer_size, __comp);
std::__merge_adaptive_resize(__new_middle, __second_cut, __last,
__len1 - __len11, __len2 - __len22,
_Distance(__len1 - __len11),
_Distance(__len2 - __len22),
__buffer, __buffer_size, __comp);
}
}

47
libstdc++-v3/include/bits/stl_algobase.h
View file

@ -72,7 +72,10 @@
#if __cplusplus >= 201103L
# include <type_traits>
#endif
#if __cplusplus > 201703L
#if __cplusplus >= 201402L
# include <bit> // std::__bit_width
#endif
#if __cplusplus >= 202002L
# include <compare>
#endif
@ -1505,29 +1508,25 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
/// This is a helper function for the sort routines and for random.tcc.
// Precondition: __n > 0.
inline _GLIBCXX_CONSTEXPR int
__lg(int __n)
{ return (int)sizeof(int) * __CHAR_BIT__ - 1 - __builtin_clz(__n); }
inline _GLIBCXX_CONSTEXPR unsigned
__lg(unsigned __n)
{ return (int)sizeof(int) * __CHAR_BIT__ - 1 - __builtin_clz(__n); }
inline _GLIBCXX_CONSTEXPR long
__lg(long __n)
{ return (int)sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
inline _GLIBCXX_CONSTEXPR unsigned long
__lg(unsigned long __n)
{ return (int)sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
inline _GLIBCXX_CONSTEXPR long long
__lg(long long __n)
{ return (int)sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
inline _GLIBCXX_CONSTEXPR unsigned long long
__lg(unsigned long long __n)
{ return (int)sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
template<typename _Tp>
inline _GLIBCXX_CONSTEXPR _Tp
__lg(_Tp __n)
{
#if __cplusplus >= 201402L
return std::__bit_width(make_unsigned_t<_Tp>(__n)) - 1;
#else
// Use +__n so it promotes to at least int.
const int __sz = sizeof(+__n);
int __w = __sz * __CHAR_BIT__ - 1;
if (__sz == sizeof(long long))
__w -= __builtin_clzll(+__n);
else if (__sz == sizeof(long))
__w -= __builtin_clzl(+__n);
else if (__sz == sizeof(int))
__w -= __builtin_clz(+__n);
return __w;
#endif
}
_GLIBCXX_BEGIN_NAMESPACE_ALGO