Switch pimpl away from std::unique_ptr due to msvc awfulness

include/cpptrace/formatting.hpp

@@ -9,8 +9,9 @@
 
 namespace cpptrace {
     class CPPTRACE_EXPORT formatter {
-        class CPPTRACE_EXPORT impl;
+        class impl;
-        std::unique_ptr<impl> pimpl;
+        // can't be a std::unique_ptr due to msvc awfulness with dllimport/dllexport and https://stackoverflow.com/q/4145605/15675011
+        impl* pimpl;
 
     public:
         formatter();

src/formatting.cpp

@@ -212,14 +212,25 @@ namespace cpptrace {
         }
     };
 
-    formatter::formatter() : pimpl(std::unique_ptr<impl>(new impl)) {}
+    formatter::formatter() : pimpl(new impl) {}
-    formatter::~formatter() = default;
+    formatter::~formatter() {
+        delete pimpl;
+    }
 
-    formatter::formatter(formatter&&) = default;
+    formatter::formatter(formatter&& other) : pimpl(detail::exchange(other.pimpl, nullptr)) {}
-    formatter::formatter(const formatter& other) : pimpl(std::unique_ptr<impl>(new impl(*other.pimpl))) {}
+    formatter::formatter(const formatter& other) : pimpl(new impl(*other.pimpl)) {}
-    formatter& formatter::operator=(formatter&&) = default;
+    formatter& formatter::operator=(formatter&& other) {
+        if(pimpl) {
+            delete pimpl;
+        }
+        pimpl = detail::exchange(other.pimpl, nullptr);
+        return *this;
+    }
     formatter& formatter::operator=(const formatter& other) {
-        pimpl = std::unique_ptr<impl>(new impl(*other.pimpl));
+        if(pimpl) {
+            delete pimpl;
+        }
+        pimpl = new impl(*other.pimpl);
         return *this;
     }
 

src/utils/utils.hpp

@@ -189,6 +189,13 @@ namespace detail {
         return static_cast<U>(v);
     }
 
+    template<typename T, typename U = T>
+    T exchange(T& obj, U&& value) {
+        T old = std::move(obj);
+        obj = std::forward<U>(value);
+        return old;
+    }
+
     struct monostate {};
 
     // TODO: Rework some stuff here. Not sure deleters should be optional or moved.