fix conversion to ‘std::streamsize’ {aka ‘long int’} from ‘size_t’ {aka ‘long unsigned int’} may change the sign of the result (ros2#715)

Signed-off-by: Grzegorz Głowacki <[email protected]>

Author: ralwing

rosidl_runtime_cpp/include/rosidl_runtime_cpp/traits.hpp

@@ -17,6 +17,7 @@
 
 #include <codecvt>
 #include <iomanip>
+#include <iosfwd>
 #include <string>
 #include <type_traits>
 
@@ -114,7 +115,7 @@ inline void value_to_yaml(const std::string & value, std::ostream & out)
     if (pos == std::string::npos) {
       pos = value.size();
     }
-    out.write(&value[index], pos - index);
+    out.write(&value[index], static_cast<std::streamsize>(pos - index));
     if (pos >= value.size()) {
       break;
     }