CommandLineInterface::link(): Print invalid link references to stderr

solc/CommandLineInterface.cpp

@@ -55,6 +55,7 @@
 #include <libsolutil/CommonIO.h>
 #include <libsolutil/JSON.h>
 
+#include <algorithm>
 #include <memory>
 
 #include <boost/filesystem.hpp>
@@ -1788,6 +1789,7 @@ bool CommandLineInterface::link()
 			)
 			{
 				serr() << "Error in binary object file " << src.first << " at position " << (it - src.second.begin()) << endl;
+				serr() << '"' << string(it, it + min(placeholderSize, static_cast<int>(end - it))) << "\" is not a valid link reference." << endl;
 				return false;
 			}