[Bug c++/71517] New: g++ gives different warnings if compiling a file directly or adding preprocess step

[albert.astals at canonical dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71517

            Bug ID: 71517
           Summary: g++ gives different warnings if compiling a file
                    directly or adding preprocess step
           Product: gcc
           Version: 5.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: albert.astals at canonical dot com
  Target Milestone: ---

Compiling the file at http://paste.ubuntu.com/17091697/

I get no warnings if just using -c

$ g++ -c -fPIC -Wsuggest-override -isystem /usr/include/x86_64-linux-gnu/qt5/
q.cpp 
$


But if i add -E step i do get warnings

$ g++ -E -fPIC -Wsuggest-override -isystem /usr/include/x86_64-linux-gnu/qt5/
q.cpp > preprocess.cpp
$ g++ -c -fPIC -Wsuggest-override -isystem /usr/include/x86_64-linux-gnu/qt5/
preprocess.cpp
q.cpp:5:75: warning: ‘virtual const QMetaObject* Moo::metaObject() const’ can
be marked override [-Wsuggest-override]
q.cpp:5:109: warning: ‘virtual void* Moo::qt_metacast(const char*)’ can be
marked override [-Wsuggest-override]
q.cpp:5:148: warning: ‘virtual int Moo::qt_metacall(QMetaObject::Call, int,
void**)’ can be marked override [-Wsuggest-override]
$


Don't know if the warning should be reported in the first case or not reported
in the second case but seems a bit inconsistent to have it in one case and not
in the other.