[libcxx-commits] [libcxx] [libc++] Fix {std, ranges}::copy for vector<bool> with small storage types (PR #131545)
via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Mar 18 09:03:30 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Peng Liu (winner245)
<details>
<summary>Changes</summary>
The current implementation of `{std, ranges}::copy` fails to copy `vector<bool>` correctly when the underlying storage type (`__storage_type`) is smaller than `int`, such as `unsigned char`, `unsigned short`, `uint8_t` and `uint16_t`. The root cause is that the unsigned small storage type undergoes integer promotion to (signed) `int`, which is then left and right shifted, leading to UB (before C++20) and sign-bit extension (since C++20) respectively. As a result, the underlying bit mask evaluations become incorrect, causing erroneous copying behavior.
This patch resolves the issue by correcting the internal bitwise operations, ensuring that `{std, ranges}::copy` operates correctly for `vector<bool>` with any custom (unsigned) storage types.
Fixes #<!-- -->131692.
---
Patch is 22.69 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/131545.diff
5 Files Affected:
- (modified) libcxx/include/__algorithm/copy.h (+9-9)
- (modified) libcxx/include/__bit_reference (+9-2)
- (modified) libcxx/include/__fwd/bit_reference.h (+4-1)
- (modified) libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp (+150)
- (modified) libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/ranges.copy.pass.cpp (+148)
``````````diff
diff --git a/libcxx/include/__algorithm/copy.h b/libcxx/include/__algorithm/copy.h
index 7454c874a4d93..ea98031df11ad 100644
--- a/libcxx/include/__algorithm/copy.h
+++ b/libcxx/include/__algorithm/copy.h
@@ -53,7 +53,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
unsigned __clz = __bits_per_word - __first.__ctz_;
difference_type __dn = std::min(static_cast<difference_type>(__clz), __n);
__n -= __dn;
- __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
+ __storage_type __m = std::__middle_mask<__storage_type>(__clz - __dn, __first.__ctz_);
__storage_type __b = *__first.__seg_ & __m;
*__result.__seg_ &= ~__m;
*__result.__seg_ |= __b;
@@ -73,7 +73,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
// do last word
if (__n > 0) {
__first.__seg_ += __nw;
- __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+ __storage_type __m = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
__storage_type __b = *__first.__seg_ & __m;
*__result.__seg_ &= ~__m;
*__result.__seg_ |= __b;
@@ -98,11 +98,11 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
unsigned __clz_f = __bits_per_word - __first.__ctz_;
difference_type __dn = std::min(static_cast<difference_type>(__clz_f), __n);
__n -= __dn;
- __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+ __storage_type __m = std::__middle_mask<__storage_type>(__clz_f - __dn, __first.__ctz_);
__storage_type __b = *__first.__seg_ & __m;
unsigned __clz_r = __bits_per_word - __result.__ctz_;
__storage_type __ddn = std::min<__storage_type>(__dn, __clz_r);
- __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
+ __m = std::__middle_mask<__storage_type>(__clz_r - __ddn, __result.__ctz_);
*__result.__seg_ &= ~__m;
if (__result.__ctz_ > __first.__ctz_)
*__result.__seg_ |= __b << (__result.__ctz_ - __first.__ctz_);
@@ -112,7 +112,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
__result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_) % __bits_per_word);
__dn -= __ddn;
if (__dn > 0) {
- __m = ~__storage_type(0) >> (__bits_per_word - __dn);
+ __m = std::__trailing_mask<__storage_type>(__bits_per_word - __dn);
*__result.__seg_ &= ~__m;
*__result.__seg_ |= __b >> (__first.__ctz_ + __ddn);
__result.__ctz_ = static_cast<unsigned>(__dn);
@@ -123,7 +123,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
// __first.__ctz_ == 0;
// do middle words
unsigned __clz_r = __bits_per_word - __result.__ctz_;
- __storage_type __m = ~__storage_type(0) << __result.__ctz_;
+ __storage_type __m = std::__leading_mask<__storage_type>(__result.__ctz_);
for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_) {
__storage_type __b = *__first.__seg_;
*__result.__seg_ &= ~__m;
@@ -134,17 +134,17 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> _
}
// do last word
if (__n > 0) {
- __m = ~__storage_type(0) >> (__bits_per_word - __n);
+ __m = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
__storage_type __b = *__first.__seg_ & __m;
__storage_type __dn = std::min(__n, static_cast<difference_type>(__clz_r));
- __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
+ __m = std::__middle_mask<__storage_type>(__clz_r - __dn, __result.__ctz_);
*__result.__seg_ &= ~__m;
*__result.__seg_ |= __b << __result.__ctz_;
__result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
__result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_) % __bits_per_word);
__n -= __dn;
if (__n > 0) {
- __m = ~__storage_type(0) >> (__bits_per_word - __n);
+ __m = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
*__result.__seg_ &= ~__m;
*__result.__seg_ |= __b >> __dn;
__result.__ctz_ = static_cast<unsigned>(__n);
diff --git a/libcxx/include/__bit_reference b/libcxx/include/__bit_reference
index 58cbd4d51c88e..f5c22fc0a3ade 100644
--- a/libcxx/include/__bit_reference
+++ b/libcxx/include/__bit_reference
@@ -82,13 +82,20 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __trailing_mask
return static_cast<_StorageType>(~static_cast<_StorageType>(0)) >> __clz;
}
+// Creates a mask of type `_StorageType` with a specified number of trailing zeros (__ctz) and sets all remaining
+// bits to one.
+template <class _StorageType>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __leading_mask(unsigned __ctz) {
+ static_assert(is_unsigned<_StorageType>::value, "__leading_mask only works with unsigned types");
+ return static_cast<_StorageType>(~static_cast<_StorageType>(0)) << __ctz;
+}
+
// Creates a mask of type `_StorageType` with a specified number of leading zeros (__clz), a specified number of
// trailing zeros (__ctz), and sets all bits in between to one.
template <class _StorageType>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __middle_mask(unsigned __clz, unsigned __ctz) {
static_assert(is_unsigned<_StorageType>::value, "__middle_mask only works with unsigned types");
- return (static_cast<_StorageType>(~static_cast<_StorageType>(0)) << __ctz) &
- std::__trailing_mask<_StorageType>(__clz);
+ return std::__leading_mask<_StorageType>(__ctz) & std::__trailing_mask<_StorageType>(__clz);
}
// This function is designed to operate correctly even for smaller integral types like `uint8_t`, `uint16_t`,
diff --git a/libcxx/include/__fwd/bit_reference.h b/libcxx/include/__fwd/bit_reference.h
index e212667f3de1f..36058d59cc22a 100644
--- a/libcxx/include/__fwd/bit_reference.h
+++ b/libcxx/include/__fwd/bit_reference.h
@@ -28,11 +28,14 @@ struct __size_difference_type_traits;
template <class _StoragePointer>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
-__fill_masked_range(_StoragePointer __word, unsigned __ctz, unsigned __clz, bool __fill_val);
+__fill_masked_range(_StoragePointer __word, unsigned __clz, unsigned __ctz, bool __fill_val);
template <class _StorageType>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __trailing_mask(unsigned __clz);
+template <class _StorageType>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __leading_mask(unsigned __ctz);
+
template <class _StorageType>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _StorageType __middle_mask(unsigned __clz, unsigned __ctz);
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp
index 3d4ee23a5a7ff..cfcaf1c8a6dd7 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp
@@ -12,10 +12,13 @@
// constexpr OutIter // constexpr after C++17
// copy(InIter first, InIter last, OutIter result);
+// XFAIL: FROZEN-CXX03-HEADERS-FIXME
+
#include <algorithm>
#include <cassert>
#include <vector>
+#include "sized_allocator.h"
#include "test_macros.h"
#include "test_iterators.h"
#include "type_algorithms.h"
@@ -109,6 +112,153 @@ TEST_CONSTEXPR_CXX20 bool test() {
assert(test_vector_bool(256));
}
+ // Validate std::copy with std::vector<bool> iterators and custom storage types.
+ // Ensure that assigned bits hold the intended values, while unassigned bits stay unchanged.
+ // Related issue: https://github.com/llvm/llvm-project/issues/131692.
+ {
+ //// Tests for std::copy with aligned bits
+
+ { // Test the first (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::copy(in.begin() + 1, in.begin() + 2, out.begin() + 1); // out[1] = false
+ assert(out[1] == false);
+ for (std::size_t i = 0; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 1)
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::copy(in.begin(), in.begin() + 1, out.begin()); // out[0] = false
+ assert(out[0] == false);
+ for (std::size_t i = 1; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(32, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(32, false, Alloc(1));
+ std::copy(in.begin() + 4, in.end() - 4, out.begin() + 4);
+ for (std::size_t i = 4; i < static_cast<std::size_t>(in.size() - 4); ++i)
+ assert(in[i] == out[i]);
+ for (std::size_t i = 0; i < 4; ++i)
+ assert(out[i] == false);
+ for (std::size_t i = 28; i < out.size(); ++i)
+ assert(out[i] == false);
+ }
+
+ { // Test the first (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::copy(in.begin() + 1, in.begin() + 3, out.begin() + 1); // out[1..2] = false
+ assert(out[1] == false);
+ assert(out[2] == false);
+ for (std::size_t i = 0; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 1 && i != 2)
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::copy(in.begin(), in.begin() + 2, out.begin()); // out[0..1] = false
+ assert(out[0] == false);
+ assert(out[1] == false);
+ for (std::size_t i = 2; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(64, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(64, false, Alloc(1));
+ std::copy(in.begin() + 8, in.end() - 8, out.begin() + 8);
+ for (std::size_t i = 8; i < static_cast<std::size_t>(in.size() - 8); ++i)
+ assert(in[i] == out[i]);
+ for (std::size_t i = 0; i < 8; ++i)
+ assert(out[i] == false);
+ for (std::size_t i = static_cast<std::size_t>(out.size() - 8); i < out.size(); ++i)
+ assert(out[i] == false);
+ }
+
+ //// Tests for std::copy with unaligned bits
+
+ { // Test the first (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::copy(in.begin() + 7, in.end(), out.begin()); // out[0] = false
+ assert(out[0] == false);
+ for (std::size_t i = 1; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::copy(in.begin(), in.begin() + 1, out.begin() + 2); // out[2] = false
+ assert(out[2] == false);
+ for (std::size_t i = 1; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 2)
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(36, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(40, false, Alloc(1));
+ std::copy(in.begin(), in.end(), out.begin() + 4);
+ for (std::size_t i = 0; i < in.size(); ++i)
+ assert(in[i] == out[i + 4]);
+ for (std::size_t i = 0; i < 4; ++i)
+ assert(out[i] == false);
+ }
+
+ { // Test the first (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::copy(in.begin() + 14, in.end(), out.begin()); // out[0..1] = false
+ assert(out[0] == false);
+ assert(out[1] == false);
+ for (std::size_t i = 2; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::copy(in.begin(), in.begin() + 2, out.begin() + 1); // out[1..2] = false
+ assert(out[1] == false);
+ assert(out[2] == false);
+ for (std::size_t i = 0; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 1 && i != 2)
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(72, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(80, false, Alloc(1));
+ std::copy(in.begin(), in.end(), out.begin() + 4);
+ for (std::size_t i = 0; i < in.size(); ++i)
+ assert(in[i] == out[i + 4]);
+ for (std::size_t i = 0; i < 4; ++i)
+ assert(out[i] == false);
+ for (std::size_t i = in.size() + 4; i < out.size(); ++i)
+ assert(out[i] == false);
+ }
+ }
+
return true;
}
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/ranges.copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/ranges.copy.pass.cpp
index 68356c80ba7f6..f541c914b401b 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/ranges.copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/ranges.copy.pass.cpp
@@ -25,6 +25,7 @@
#include <vector>
#include "almost_satisfies_types.h"
+#include "sized_allocator.h"
#include "test_iterators.h"
#include "test_macros.h"
#include "type_algorithms.h"
@@ -237,6 +238,153 @@ constexpr bool test() {
assert(test_vector_bool(199));
assert(test_vector_bool(256));
}
+
+ // Validate std::ranges::copy with std::vector<bool> iterators and custom storage types.
+ // Ensure that assigned bits hold the intended values, while unassigned bits stay unchanged.
+ // Related issue: https://github.com/llvm/llvm-project/issues/131692.
+ {
+ //// Tests for std::ranges::copy with aligned bits
+
+ { // Test the first (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin() + 1, in.begin() + 2), out.begin() + 1); // out[1] = false
+ assert(out[1] == false);
+ for (std::size_t i = 0; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 1)
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin(), in.begin() + 1), out.begin()); // out[0] = false
+ assert(out[0] == false);
+ for (std::size_t i = 1; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(32, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(32, false, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin() + 4, in.end() - 4), out.begin() + 4);
+ for (std::size_t i = 4; i < static_cast<std::size_t>(in.size() - 4); ++i)
+ assert(in[i] == out[i]);
+ for (std::size_t i = 0; i < 4; ++i)
+ assert(out[i] == false);
+ for (std::size_t i = 28; i < out.size(); ++i)
+ assert(out[i] == false);
+ }
+
+ { // Test the first (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin() + 1, in.begin() + 3), out.begin() + 1); // out[1..2] = false
+ assert(out[1] == false);
+ assert(out[2] == false);
+ for (std::size_t i = 0; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ if (i != 1 && i != 2)
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(16, false, Alloc(1));
+ std::vector<bool, Alloc> out(16, true, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin(), in.begin() + 2), out.begin()); // out[0..1] = false
+ assert(out[0] == false);
+ assert(out[1] == false);
+ for (std::size_t i = 2; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test middle (whole) words for uint16_t
+ using Alloc = sized_allocator<bool, std::uint16_t, std::int16_t>;
+ std::vector<bool, Alloc> in(64, true, Alloc(1));
+ for (std::size_t i = 0; i < in.size(); i += 2)
+ in[i] = false;
+ std::vector<bool, Alloc> out(64, false, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin() + 8, in.end() - 8), out.begin() + 8);
+ for (std::size_t i = 8; i < static_cast<std::size_t>(in.size() - 8); ++i)
+ assert(in[i] == out[i]);
+ for (std::size_t i = 0; i < 8; ++i)
+ assert(out[i] == false);
+ for (std::size_t i = static_cast<std::size_t>(out.size() - 8); i < out.size(); ++i)
+ assert(out[i] == false);
+ }
+
+ //// Tests for std::ranges::copy with unaligned bits
+
+ { // Test the first (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, Alloc> out(8, true, Alloc(1));
+ std::ranges::copy(std::ranges::subrange(in.begin() + 7, in.end()), out.begin()); // out[0] = false
+ assert(out[0] == false);
+ for (std::size_t i = 1; i < out.size(); ++i) // Ensure that unassigned bits remain unchanged
+ assert(out[i] == true);
+ }
+ { // Test the last (partial) word for uint8_t
+ using Alloc = sized_allocator<bool, std::uint8_t, std::int8_t>;
+ std::vector<bool, Alloc> in(8, false, Alloc(1));
+ std::vector<bool, All...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/131545
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