fix issue #70

Author: greg7mdp

examples/makefile

@@ -2,7 +2,7 @@ CXXFLAGS     = -O2 -std=c++11 -I..
 CXXFLAGS    += -Wall -pedantic -Wextra
 SPP_DEPS_1   =  spp.h spp_utils.h spp_dlalloc.h spp_traits.h spp_config.h
 SPP_DEPS     = $(addprefix ../sparsepp/,$(SPP_DEPS_1))
-TARGETS      = emplace hash_std serialize_file serialize_stream serialize_large
+TARGETS      = emplace piecewise hash_std serialize_file serialize_stream serialize_large
 
 ifeq ($(OS),Windows_NT)
     LDFLAGS  = -lpsapi

examples/piecewise.cc

@@ -0,0 +1,24 @@
+#include <unordered_map>
+#include <string>
+#include <iostream>
+#include <sparsepp/spp.h>
+
+#include <sstream>
+
+int main()
+{
+    using StringPtr = std::unique_ptr<std::string>;
+
+#if 1
+    using StringPtrContainer = spp::sparse_hash_map<StringPtr, StringPtr>;
+#else
+    using StringPtrContainer = std::unordered_map<StringPtr, StringPtr>;
+#endif
+
+    StringPtrContainer c;
+
+    c.emplace(std::piecewise_construct, 
+              std::forward_as_tuple(new std::string{ "key" }),
+              std::forward_as_tuple(new std::string{ "value" }));
+}
+

sparsepp/spp.h

@@ -1064,6 +1064,7 @@ class sparsegroup
     // T can be std::pair<const K, V>, but sometime we need to cast to a mutable type
     // ------------------------------------------------------------------------------
     typedef typename spp_::cvt<T>::type                    mutable_value_type;
+    typedef mutable_value_type &                           mutable_reference;
     typedef mutable_value_type *                           mutable_pointer;
     typedef const mutable_value_type *                     const_mutable_pointer;
 
@@ -1332,9 +1333,9 @@ class sparsegroup
     void _init_val(mutable_value_type *p, reference val)
     {
 #if !defined(SPP_NO_CXX11_RVALUE_REFERENCES)
-        ::new (p) value_type(std::move(val));
+        ::new (p) value_type(std::move((mutable_reference)val));
 #else
-        ::new (p) value_type(val);
+        ::new (p) value_type((mutable_reference)val);
 #endif
     }
 
@@ -1348,7 +1349,7 @@ class sparsegroup
     void _set_val(value_type *p, reference val)
     {
 #if !defined(SPP_NO_CXX11_RVALUE_REFERENCES)
-        *(mutable_pointer)p = std::move(val);
+        *(mutable_pointer)p = std::move((mutable_reference)val);
 #else
         using std::swap;
         swap(*(mutable_pointer)p, *(mutable_pointer)&val);