The gcc warnings parser just ignores errors happening in files that have uncommon extensions.
In our project we put C++ template implementations in .inl files, but errors insides these files will just get ignored.
The regular expression that parses messages seems to be rather restrictive about file extensions.
I think of one other extension for template implementation that is probably not supported: ".tpp".
Moreover, if an error is raised when instanciating a C++ standard library class, it will probably not be reported by the plugin because these headers do not have extension.
Maybe it would be better to make extension optional and allow any characters.
I joined a piece of build log exposing the problem with .inl files.