[libc++] Fix ambiguous call to std::max in vector<bool> #119801
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@llvm/pr-subscribers-libcxx Author: Peng Liu (winner245) ChangesThis PR addresses a compilation error in The following code snippet reproduces the bug in #include <exception>
#include <iostream>
#include <limits>
#include <memory>
#include <vector>
template <typename T, typename SIZE_TYPE = std::size_t, typename DIFF_TYPE = std::ptrdiff_t>
class CustomSizedAllocator {
template <typename U, typename Sz, typename Diff>
friend class CustomSizedAllocator;
public:
using value_type = T;
using size_type = SIZE_TYPE;
using difference_type = DIFF_TYPE;
using propagate_on_container_swap = std::true_type;
explicit CustomSizedAllocator(int i = 0) : data_(i) {}
template <typename U, typename Sz, typename Diff>
constexpr CustomSizedAllocator(const CustomSizedAllocator<U, Sz, Diff>& a) noexcept : data_(a.data_) {}
constexpr T* allocate(size_type n) {
if (n > max_size())
throw std::bad_array_new_length();
return std::allocator<T>().allocate(n);
}
constexpr void deallocate(T* p, size_type n) noexcept { std::allocator<T>().deallocate(p, n); }
constexpr size_type max_size() const noexcept { return std::numeric_limits<size_type>::max() / sizeof(value_type); }
int get() { return data_; }
private:
int data_;
constexpr friend bool operator==(const CustomSizedAllocator& a, const CustomSizedAllocator& b) {
return a.data_ == b.data_;
}
constexpr friend bool operator!=(const CustomSizedAllocator& a, const CustomSizedAllocator& b) {
return a.data_ != b.data_;
}
};
int main() {
using Alloc = CustomSizedAllocator<bool, std::uint16_t, std::int16_t>;
std::vector<bool, Alloc> c{Alloc{1}};
c.resize(10);
return 0;
}This code fails to compile in libc++, while it compiles successfully in other standard library implementations. The underlying issue is found in the following line of code within return std::max(2 * __cap, __align_it(__new_size));where the first operand's result type is promoted to int, while the second operand retains the The solution is straightforward: explicitly specify the template type for Full diff: https://github.com/llvm/llvm-project/pull/119801.diff 4 Files Affected:
diff --git a/libcxx/include/__cxx03/string b/libcxx/include/__cxx03/string
index c4431dcb04d41e..c29f74290bd416 100644
--- a/libcxx/include/__cxx03/string
+++ b/libcxx/include/__cxx03/string
@@ -2483,7 +2483,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::__
__throw_length_error();
pointer __old_p = __get_pointer();
size_type __cap =
- __old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms - 1;
+ __old_cap < __ms / 2 - __alignment
+ ? __recommend(std::max<size_type>(__old_cap + __delta_cap, 2 * __old_cap))
+ : __ms - 1;
__annotate_delete();
auto __allocation = std::__allocate_at_least(__alloc(), __cap + 1);
pointer __p = __allocation.ptr;
@@ -2526,7 +2528,9 @@ _LIBCPP_DEPRECATED_("use __grow_by_without_replace") basic_string<_CharT, _Trait
__throw_length_error();
pointer __old_p = __get_pointer();
size_type __cap =
- __old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms - 1;
+ __old_cap < __ms / 2 - __alignment
+ ? __recommend(std::max<size_type>(__old_cap + __delta_cap, 2 * __old_cap))
+ : __ms - 1;
__annotate_delete();
auto __allocation = std::__allocate_at_least(__alloc(), __cap + 1);
pointer __p = __allocation.ptr;
diff --git a/libcxx/include/__cxx03/vector b/libcxx/include/__cxx03/vector
index 6ee35b4e36258f..80da74ded67b7a 100644
--- a/libcxx/include/__cxx03/vector
+++ b/libcxx/include/__cxx03/vector
@@ -2328,7 +2328,7 @@ vector<bool, _Allocator>::__recommend(size_type __new_size) const {
const size_type __cap = capacity();
if (__cap >= __ms / 2)
return __ms;
- return std::max(2 * __cap, __align_it(__new_size));
+ return std::max<size_type>(2 * __cap, __align_it(__new_size));
}
// Default constructs __n objects starting at __end_
diff --git a/libcxx/include/__vector/vector_bool.h b/libcxx/include/__vector/vector_bool.h
index 36eb7f350ac406..26b172af9138db 100644
--- a/libcxx/include/__vector/vector_bool.h
+++ b/libcxx/include/__vector/vector_bool.h
@@ -527,7 +527,7 @@ vector<bool, _Allocator>::__recommend(size_type __new_size) const {
const size_type __cap = capacity();
if (__cap >= __ms / 2)
return __ms;
- return std::max(2 * __cap, __align_it(__new_size));
+ return std::max<size_type>(2 * __cap, __align_it(__new_size));
}
// Default constructs __n objects starting at __end_
diff --git a/libcxx/include/string b/libcxx/include/string
index 17bf4b3b98bf34..911b67cfcf26e8 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -2518,7 +2518,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::__
__throw_length_error();
pointer __old_p = __get_pointer();
size_type __cap =
- __old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms - 1;
+ __old_cap < __ms / 2 - __alignment
+ ? __recommend(std::max<size_type>(__old_cap + __delta_cap, 2 * __old_cap))
+ : __ms - 1;
__annotate_delete();
auto __guard = std::__make_scope_guard(__annotate_new_size(*this));
auto __allocation = std::__allocate_at_least(__alloc_, __cap + 1);
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This PR fixes an ambiguous call to
std::maxinvector<bool>and also improves similar usage ofstd::maxwithinstd::basic_stringto prevent potential issues.Closes #121713.