[libcxx-commits] [libcxx] f65d7fd - [libc++][vector] Fixes shrink_to_fit. (#97895)
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Sat Jul 20 03:55:48 PDT 2024
Author: Mark de Wever
Date: 2024-07-20T12:55:44+02:00
New Revision: f65d7fdcf81f1fb01df3446b254f3304589f19c4
URL: https://github.com/llvm/llvm-project/commit/f65d7fdcf81f1fb01df3446b254f3304589f19c4
DIFF: https://github.com/llvm/llvm-project/commit/f65d7fdcf81f1fb01df3446b254f3304589f19c4.diff
LOG: [libc++][vector] Fixes shrink_to_fit. (#97895)
This assures shrink_to_fit does not increase the allocated size.
Partly addresses https://github.com/llvm/llvm-project/issues/95161
---------
Co-authored-by: Mital Ashok <mital.vaja at googlemail.com>
Added:
Modified:
libcxx/include/vector
libcxx/test/std/containers/sequences/vector/vector.capacity/shrink_to_fit.pass.cpp
Removed:
################################################################################
diff --git a/libcxx/include/vector b/libcxx/include/vector
index aaf51d18fe30f..45980043a3c15 100644
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -1443,7 +1443,11 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void vector<_Tp, _Allocator>::shrink_to_fit() _NOE
#endif // _LIBCPP_HAS_NO_EXCEPTIONS
allocator_type& __a = this->__alloc();
__split_buffer<value_type, allocator_type&> __v(size(), size(), __a);
- __swap_out_circular_buffer(__v);
+ // 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 (__v.capacity() < capacity())
+ __swap_out_circular_buffer(__v);
#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
} catch (...) {
}
diff --git a/libcxx/test/std/containers/sequences/vector/vector.capacity/shrink_to_fit.pass.cpp b/libcxx/test/std/containers/sequences/vector/vector.capacity/shrink_to_fit.pass.cpp
index 8851e2a9ed0c7..e39afb2d48f0a 100644
--- a/libcxx/test/std/containers/sequences/vector/vector.capacity/shrink_to_fit.pass.cpp
+++ b/libcxx/test/std/containers/sequences/vector/vector.capacity/shrink_to_fit.pass.cpp
@@ -71,11 +71,56 @@ TEST_CONSTEXPR_CXX20 bool tests() {
return true;
}
+#if TEST_STD_VER >= 23
+template <typename T>
+struct increasing_allocator {
+ using value_type = T;
+ std::size_t min_elements = 1000;
+ increasing_allocator() = default;
+
+ template <typename U>
+ constexpr increasing_allocator(const increasing_allocator<U>& other) noexcept : min_elements(other.min_elements) {}
+
+ constexpr std::allocation_result<T*> allocate_at_least(std::size_t n) {
+ if (n < min_elements)
+ n = min_elements;
+ min_elements += 1000;
+ return std::allocator<T>{}.allocate_at_least(n);
+ }
+ constexpr T* allocate(std::size_t n) { return allocate_at_least(n).ptr; }
+ constexpr void deallocate(T* p, std::size_t n) noexcept { std::allocator<T>{}.deallocate(p, n); }
+};
+
+template <typename T, typename U>
+bool operator==(increasing_allocator<T>, increasing_allocator<U>) {
+ return true;
+}
+
+// https://github.com/llvm/llvm-project/issues/95161
+constexpr bool test_increasing_allocator() {
+ std::vector<int, increasing_allocator<int>> v;
+ v.push_back(1);
+ assert(is_contiguous_container_asan_correct(v));
+ std::size_t capacity = v.capacity();
+ v.shrink_to_fit();
+ assert(v.capacity() <= capacity);
+ assert(v.size() == 1);
+ assert(is_contiguous_container_asan_correct(v));
+
+ return true;
+}
+#endif // TEST_STD_VER >= 23
+
int main(int, char**)
{
- tests();
+ tests();
#if TEST_STD_VER > 17
static_assert(tests());
#endif
+#if TEST_STD_VER >= 23
+ test_increasing_allocator();
+ static_assert(test_increasing_allocator());
+#endif
+
return 0;
}
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