Fix bug #20335 - memory leak when move-constructing a string with unequal allocator. Thanks to Thomas Koeppe for the report

llvm-svn: 213269

libcxx/include/string

@@ -2136,11 +2136,13 @@ inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
     : __r_(__a)
 {
-    if (__a == __str.__alloc() || !__str.__is_long())
-        __r_.first().__r = __str.__r_.first().__r;
-    else
+    if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
         __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
+    else
+    {
+        __r_.first().__r = __str.__r_.first().__r;
         __str.__zero();
+    }
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
     if (__is_long())

libcxx/test/strings/basic.string/string.cons/move_alloc.pass.cpp

@@ -45,6 +45,16 @@ int main()
     test(S("1"), A(5));
     test(S("1234567890123456789012345678901234567890123456789012345678901234567890"), A(7));
     }
+
+    int alloc_count = test_alloc_base::alloc_count;
+    {
+    typedef test_allocator<char> A;
+    typedef std::basic_string<char, std::char_traits<char>, A> S;
+    S s1 ( "Twas brillig, and the slivy toves did gyre and gymbal in the wabe" );
+    S s2 (std::move(s1), A(1));
+    }
+    assert ( test_alloc_base::alloc_count == alloc_count );
+    
 #if __cplusplus >= 201103L
     {
     typedef min_allocator<char> A;