[libc++] Fix build failure with _LIBCPP_DEBUG=0 when iterators return values instead of references
There are many STL algorithms (such as lexicographical_compare) that compare
values pointed to by iterators like so:
__comp(*it1, *it2);
When building with `_LIBCPP_DEBUG=0`, comparators are wrapped in `__debug_less`
which does some additional validation. But `__debug_less::operator()` takes
non-const references, so if the type of `*it1` is int, not int&, then the build
will fail.
This change adds a `const&` overload for `operator()` to fix the build.
Differential Revision: https://reviews.llvm.org/D60592
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@358423 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/algorithm b/include/algorithm
index 22adcc8..244ae2d 100644
--- a/include/algorithm
+++ b/include/algorithm
@@ -785,6 +785,15 @@
__debug_less(_Compare& __c) : __comp_(__c) {}
template <class _Tp, class _Up>
+ bool operator()(const _Tp& __x, const _Up& __y)
+ {
+ bool __r = __comp_(__x, __y);
+ if (__r)
+ __do_compare_assert(0, __y, __x);
+ return __r;
+ }
+
+ template <class _Tp, class _Up>
_LIBCPP_CONSTEXPR_AFTER_CXX17
bool operator()(_Tp& __x, _Up& __y)
{
diff --git a/test/libcxx/algorithms/debug_less.pass.cpp b/test/libcxx/algorithms/debug_less.pass.cpp
index 4f92854..5386303 100644
--- a/test/libcxx/algorithms/debug_less.pass.cpp
+++ b/test/libcxx/algorithms/debug_less.pass.cpp
@@ -235,10 +235,45 @@
}
}
+struct ValueIterator {
+ using iterator_category = std::input_iterator_tag;
+ using value_type = size_t;
+ using difference_type = ptrdiff_t;
+ using reference = size_t;
+ using pointer = size_t*;
+
+ ValueIterator() = default;
+
+ reference operator*() { return 0; }
+ ValueIterator& operator++() { return *this; }
+
+ friend bool operator==(ValueIterator, ValueIterator) { return true; }
+ friend bool operator!=(ValueIterator, ValueIterator) { return false; }
+};
+
+void test_value_iterator() {
+ // Ensure no build failures when iterators return values, not references.
+ assert(0 == std::lexicographical_compare(ValueIterator{}, ValueIterator{},
+ ValueIterator{}, ValueIterator{}));
+}
+
+void test_value_categories() {
+ std::less<int> l;
+ std::__debug_less<std::less<int>> dl(l);
+ int lvalue = 42;
+ const int const_lvalue = 101;
+
+ assert(dl(lvalue, const_lvalue));
+ assert(dl(/*rvalue*/1, lvalue));
+ assert(dl(static_cast<int&&>(1), static_cast<const int&&>(2)));
+}
+
int main(int, char**) {
test_passing();
test_failing();
test_upper_and_lower_bound();
test_non_const_arg_cmp();
+ test_value_iterator();
+ test_value_categories();
return 0;
}
