From cb6f663f9d79d7134ae6ecaff9a25342c40aeb5d Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 28 Mar 2023 11:12:58 +0100 Subject: [PATCH] libstdc++: More fixes for null pointers used with std::char_traits The std::char_traits member functions require that [p,p+n) is a valid range, which is true for p==nullptr iff n==0. But we must not call memcpy, memset etc, in that case, as they require non-null pointers even when n==0. This std::char_traits and std::char_traits explicit specializations are already correct, but the primary template has some bugs. libstdc++-v3/ChangeLog: * include/bits/char_traits.h (char_traits::copy): Return without using memcpy if n==0. (char_traits::assign): Likewise for memset. --- libstdc++-v3/include/bits/char_traits.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h index cfc7d0f0e14..68ed827f982 100644 --- a/libstdc++-v3/include/bits/char_traits.h +++ b/libstdc++-v3/include/bits/char_traits.h @@ -263,6 +263,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION char_traits<_CharT>:: copy(char_type* __s1, const char_type* __s2, std::size_t __n) { + if (__n == 0) + return __s1; #if __cplusplus >= 202002L if (std::__is_constant_evaluated()) { @@ -271,7 +273,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return __s1; } #endif - __builtin_memcpy(__s1, __s2, __n * sizeof(char_type)); return __s1; } @@ -293,9 +294,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if _GLIBCXX17_CONSTEXPR (sizeof(_CharT) == 1 && __is_trivial(_CharT)) { - unsigned char __c; - __builtin_memcpy(&__c, __builtin_addressof(__a), 1); - __builtin_memset(__s, __c, __n); + if (__n) + { + unsigned char __c; + __builtin_memcpy(&__c, __builtin_addressof(__a), 1); + __builtin_memset(__s, __c, __n); + } } else {