[libcxx-commits] [libcxx] 59f57be - Revert "[libc++] Simplify the implementation of reserve() and shrink_to_fit() (#113453)"
Benjamin Kramer via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Nov 29 04:20:04 PST 2024
Author: Benjamin Kramer
Date: 2024-11-29T13:18:28+01:00
New Revision: 59f57be94f38758616b1339b293b43af845571af
URL: https://github.com/llvm/llvm-project/commit/59f57be94f38758616b1339b293b43af845571af
DIFF: https://github.com/llvm/llvm-project/commit/59f57be94f38758616b1339b293b43af845571af.diff
LOG: Revert "[libc++] Simplify the implementation of reserve() and shrink_to_fit() (#113453)"
This reverts commit d648eed5899c4be10f1f7866eebef2bc171e673f. Breaks
anything that relies on sized deallocation, e.g. asan and tcmalloc.
Added:
Modified:
libcxx/include/string
Removed:
################################################################################
diff --git a/libcxx/include/string b/libcxx/include/string
index 157ca6a6400a20..bf7fc3c37ecd7a 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1884,6 +1884,8 @@ private:
operator==(const basic_string<char, char_traits<char>, _Alloc>& __lhs,
const basic_string<char, char_traits<char>, _Alloc>& __rhs) _NOEXCEPT;
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __shrink_or_extend(size_type __target_capacity);
+
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS bool
__is_long() const _NOEXCEPT {
if (__libcpp_is_constant_evaluated() && __builtin_constant_p(__rep_.__l.__is_long_)) {
@@ -2078,21 +2080,6 @@ private:
#endif
}
- // Disable ASan annotations and enable them again when going out of scope. It is assumed that the string is in a valid
- // state at that point, so `size()` can be called safely.
- struct [[__nodiscard__]] __annotation_guard {
- __annotation_guard(const __annotation_guard&) = delete;
- __annotation_guard& operator=(const __annotation_guard&) = delete;
-
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __annotation_guard(basic_string& __str) : __str_(__str) {
- __str_.__annotate_delete();
- }
-
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__annotation_guard() { __str_.__annotate_new(__str_.size()); }
-
- basic_string& __str_;
- };
-
template <size_type __a>
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 size_type __align_it(size_type __s) _NOEXCEPT {
return (__s + (__a - 1)) & ~(__a - 1);
@@ -3371,16 +3358,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::re
if (__requested_capacity <= capacity())
return;
- __annotation_guard __g(*this);
- auto __allocation = std::__allocate_at_least(__alloc_, __recommend(__requested_capacity) + 1);
- auto __size = size();
- __begin_lifetime(__allocation.ptr, __allocation.count);
- traits_type::copy(std::__to_address(__allocation.ptr), data(), __size + 1);
- if (__is_long())
- __alloc_traits::deallocate(__alloc_, __get_long_pointer(), __get_long_size() + 1);
- __set_long_cap(__allocation.count);
- __set_long_size(__size);
- __set_long_pointer(__allocation.ptr);
+ __shrink_or_extend(__recommend(__requested_capacity));
}
template <class _CharT, class _Traits, class _Allocator>
@@ -3389,46 +3367,69 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocat
if (__target_capacity == capacity())
return;
- _LIBCPP_ASSERT_INTERNAL(__is_long(), "Trying to shrink small string");
+ __shrink_or_extend(__target_capacity);
+}
- // We're a long string and we're shrinking into the small buffer.
- if (__fits_in_sso(__target_capacity)) {
- __annotation_guard __g(*this);
- auto __ptr = __get_long_pointer();
- auto __size = __get_long_size();
- auto __cap = __get_long_cap();
- traits_type::copy(std::__to_address(__get_short_pointer()), std::__to_address(__ptr), __size + 1);
- __set_short_size(__size);
- __alloc_traits::deallocate(__alloc_, __ptr, __cap);
- return;
- }
+template <class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void
+basic_string<_CharT, _Traits, _Allocator>::__shrink_or_extend(size_type __target_capacity) {
+ __annotate_delete();
+ auto __guard = std::__make_scope_guard(__annotate_new_size(*this));
+ size_type __cap = capacity();
+ size_type __sz = size();
+ pointer __new_data, __p;
+ bool __was_long, __now_long;
+ if (__fits_in_sso(__target_capacity)) {
+ __was_long = true;
+ __now_long = false;
+ __new_data = __get_short_pointer();
+ __p = __get_long_pointer();
+ } else {
+ if (__target_capacity > __cap) {
+ // Extend
+ // - called from reserve should propagate the exception thrown.
+ auto __allocation = std::__allocate_at_least(__alloc_, __target_capacity + 1);
+ __new_data = __allocation.ptr;
+ __target_capacity = __allocation.count - 1;
+ } else {
+ // Shrink
+ // - called from shrink_to_fit should not throw.
+ // - called from reserve may throw but is not required to.
#if _LIBCPP_HAS_EXCEPTIONS
- try {
+ try {
#endif // _LIBCPP_HAS_EXCEPTIONS
- __annotation_guard __g(*this);
- auto __size = size();
- auto __allocation = std::__allocate_at_least(__alloc_, __target_capacity + 1);
-
- // The Standard mandates shrink_to_fit() does not increase the capacity.
- // With equal capacity keep the existing buffer. This avoids extra work
- // due to swapping the elements.
- if (__allocation.count - 1 > capacity()) {
- __alloc_traits::deallocate(__alloc_, __allocation.ptr, __allocation.count);
- return;
- }
-
- __begin_lifetime(__allocation.ptr, __allocation.count);
- auto __ptr = __get_long_pointer();
- traits_type::copy(std::__to_address(__allocation.ptr), std::__to_address(__ptr), __size + 1);
- __alloc_traits::deallocate(__alloc_, __ptr, __get_long_cap());
- __set_long_cap(__allocation.count);
- __set_long_pointer(__allocation.ptr);
+ auto __allocation = std::__allocate_at_least(__alloc_, __target_capacity + 1);
+
+ // The Standard mandates shrink_to_fit() does not increase the capacity.
+ // With equal capacity keep the existing buffer. This avoids extra work
+ // due to swapping the elements.
+ if (__allocation.count - 1 > capacity()) {
+ __alloc_traits::deallocate(__alloc_, __allocation.ptr, __allocation.count);
+ return;
+ }
+ __new_data = __allocation.ptr;
+ __target_capacity = __allocation.count - 1;
#if _LIBCPP_HAS_EXCEPTIONS
- } catch (...) {
- return;
- }
+ } catch (...) {
+ return;
+ }
#endif // _LIBCPP_HAS_EXCEPTIONS
+ }
+ __begin_lifetime(__new_data, __target_capacity + 1);
+ __now_long = true;
+ __was_long = __is_long();
+ __p = __get_pointer();
+ }
+ traits_type::copy(std::__to_address(__new_data), std::__to_address(__p), size() + 1);
+ if (__was_long)
+ __alloc_traits::deallocate(__alloc_, __p, __cap + 1);
+ if (__now_long) {
+ __set_long_cap(__target_capacity + 1);
+ __set_long_size(__sz);
+ __set_long_pointer(__new_data);
+ } else
+ __set_short_size(__sz);
}
template <class _CharT, class _Traits, class _Allocator>
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