From a0e11004218e635136e71b8eebb55fed45f2040c Mon Sep 17 00:00:00 2001
From: Glen Fernandes <glen.fernandes@gmail.com>
Date: Mon, 29 Apr 2019 00:23:59 -0400
Subject: [PATCH] Add noinit_adapt() free function utility

---
 doc/noinit_adaptor.qbk                | 12 ++++-
 include/boost/core/noinit_adaptor.hpp |  7 +++
 test/noinit_adaptor_test.cpp          | 67 ++++++++++++---------------
 3 files changed, 47 insertions(+), 39 deletions(-)

diff --git a/doc/noinit_adaptor.qbk b/doc/noinit_adaptor.qbk
index f622f58..585508a 100644
--- a/doc/noinit_adaptor.qbk
+++ b/doc/noinit_adaptor.qbk
@@ -34,8 +34,7 @@ initialization of elements of a trivial type, which are later assigned values.
 
 int main()
 {
-    std::vector<int,
-        boost::noinit_adaptor<std::allocator<int> > > v(5);
+    std::vector<int, boost::noinit_adaptor<std::allocator<int> > > v(5);
     std::iota(v.begin(), v.end(), 1);
 }
 ```
@@ -136,6 +135,15 @@ const noinit_adaptor<U>& rhs) noexcept;`]
 
 [endsect]
 
+[section Free functions]
+
+[variablelist
+[[`template<class A> noinit_adaptor<A> noinit_adapt(const A& a) noexcept;`]
+[[variablelist
+[[Returns][`noinit_adaptor<A>(a)`.]]]]]]
+
+[endsect]
+
 [endsect]
 
 [endsect]
diff --git a/include/boost/core/noinit_adaptor.hpp b/include/boost/core/noinit_adaptor.hpp
index 959da95..eb92102 100644
--- a/include/boost/core/noinit_adaptor.hpp
+++ b/include/boost/core/noinit_adaptor.hpp
@@ -91,6 +91,13 @@ operator!=(const noinit_adaptor<T>& lhs,
     return !(lhs == rhs);
 }
 
+template<class A>
+inline noinit_adaptor<A>
+noinit_adapt(const A& a) BOOST_NOEXCEPT
+{
+    return noinit_adaptor<A>(a);
+}
+
 } /* boost */
 
 #endif
diff --git a/test/noinit_adaptor_test.cpp b/test/noinit_adaptor_test.cpp
index 12fb941..8f394ea 100644
--- a/test/noinit_adaptor_test.cpp
+++ b/test/noinit_adaptor_test.cpp
@@ -19,36 +19,36 @@ public:
         typedef creator<U> other;
     };
 
-    creator(int* count)
-        : count_(count) { }
+    creator(int state)
+        : state_(state) { }
 
     template<class U>
     creator(const creator<U>& other)
-        : count_(other.count()) { }
+        : state_(other.state()) { }
 
     template<class U, class V>
     void construct(U*, const V&) {
-        ++(*count_);
+        BOOST_ERROR("construct");
     }
 
     template<class U>
     void destroy(U*) {
-        --(*count_);
+        BOOST_ERROR("destroy");
     }
 
-    int* count() const {
-        return count_;
+    int state() const {
+        return state_;
     }
 
 private:
-    int* count_;
+    int state_;
 };
 
 template<class T, class U>
 inline bool
 operator==(const creator<T>& lhs, const creator<U>& rhs)
 {
-    return lhs.count() == rhs.count();
+    return lhs.state() == rhs.state();
 }
 
 template<class T, class U>
@@ -73,35 +73,28 @@ private:
     int value_;
 };
 
+inline bool
+operator==(const type& lhs, const type& rhs)
+{
+    return lhs.value() == rhs.value();
+}
+
+template<class A>
+void test(const A& allocator)
+{
+    std::vector<int, A> v(allocator);
+    v.push_back(1);
+    BOOST_TEST(v.front() == 1);
+    v.clear();
+    v.resize(5);
+    v.front() = 1;
+}
+
 int main()
 {
-    {
-        int c = 0;
-        std::vector<int, boost::noinit_adaptor<creator<int> > > v(&c);
-        BOOST_TEST(c == 0);
-        v.push_back(1);
-        BOOST_TEST(v.front() == 1);
-        v.push_back(2);
-        BOOST_TEST(c == 0);
-        v.clear();
-        BOOST_TEST(c == 0);
-        v.resize(5);
-        BOOST_TEST(c == 0);
-        v.front() = 1;
-    }
-    {
-        int c = 0;
-        std::vector<type, boost::noinit_adaptor<creator<type> > > v(&c);
-        BOOST_TEST(c == 0);
-        v.push_back(1);
-        BOOST_TEST(v.front().value() == 1);
-        v.push_back(2);
-        BOOST_TEST(c == 0);
-        v.clear();
-        BOOST_TEST(c == 0);
-        v.resize(5);
-        BOOST_TEST(c == 0);
-        v.front() = 1;
-    }
+    test(boost::noinit_adaptor<creator<int> >(1));
+    test(boost::noinit_adaptor<creator<type> >(2));
+    test(boost::noinit_adapt(creator<int>(3)));
+    test(boost::noinit_adapt(creator<type>(4)));
     return boost::report_errors();
 }