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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-5080] libstdc++: Fix some algos for 16-bit size_t [PR108221] Date: Tue, 10 Jan 2023 10:10:09 +0000 (GMT) [thread overview] Message-ID: <20230110101009.5EAF93858C52@sourceware.org> (raw) https://gcc.gnu.org/g:769fae76dfd71045fe062e7b1edef0f59e50371d commit r13-5080-g769fae76dfd71045fe062e7b1edef0f59e50371d Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Jan 9 10:45:31 2023 +0000 libstdc++: Fix some algos for 16-bit size_t [PR108221] 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. Diff: --- libstdc++-v3/include/bits/stl_algo.h | 5 ++-- libstdc++-v3/include/bits/stl_algobase.h | 47 ++++++++++++++++---------------- 2 files changed, 26 insertions(+), 26 deletions(-) diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h index 6386918fc8b..eed04b3c1b8 100644 --- a/libstdc++-v3/include/bits/stl_algo.h +++ b/libstdc++-v3/include/bits/stl_algo.h @@ -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); } } diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h index ae898ed3706..566b6d9c4bc 100644 --- a/libstdc++-v3/include/bits/stl_algobase.h +++ b/libstdc++-v3/include/bits/stl_algobase.h @@ -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
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