Add Q_FALLTHROUGH for Qt < 5.8

... and make use of it.
With gcc 7, the new option -Wimplicit-fallthrough is introduced and
added to the -Wextra set, triggering dozens of warnings in our sources.
Therefore, we annotate all obviously intended fall-throughs. The ones
that are still left are unclear and need to be checked by the respective
maintainer.

Change-Id: I44ead33cd42a4b41c28ee5fcb5a31db272710bbc
Reviewed-by: Nikita Baryshnikov <nib952051@gmail.com>
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

4 files changed, 59 insertions, 1 deletions

diff --git a/src/libs/3rdparty/cplusplus/Parser.cpp b/src/libs/3rdparty/cplusplus/Parser.cpp
index 8754206a0b..16f351077a 100644
--- a/src/libs/3rdparty/cplusplus/Parser.cpp
+++ b/src/libs/3rdparty/cplusplus/Parser.cpp
@@ -27,6 +27,8 @@
 #include "ObjectiveCTypeQualifiers.h"
 #include "QtContextKeywords.h"
 
+#include <utils/qtcfallthrough.h>
+
 #include <unordered_map>
 #include <utility>
 
@@ -442,7 +444,7 @@ bool Parser::skipUntilStatement()
             case T_AT_THROW:
                 if (_languageFeatures.objCEnabled)
                     return true;
-
+                Q_FALLTHROUGH();
             default:
                 consumeToken();
         }
diff --git a/src/libs/utils/qtcfallthrough.h b/src/libs/utils/qtcfallthrough.h
new file mode 100644
index 0000000000..6eba622837
--- /dev/null
+++ b/src/libs/utils/qtcfallthrough.h
@@ -0,0 +1,54 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QtGlobal>
+
+#ifndef Q_FALLTHROUGH
+#ifndef QT_HAS_CPP_ATTRIBUTE
+#ifdef __has_cpp_attribute
+#  define QT_HAS_CPP_ATTRIBUTE(x)       __has_cpp_attribute(x)
+#else
+#  define QT_HAS_CPP_ATTRIBUTE(x)       0
+#endif
+#endif
+#if defined(__cplusplus)
+#if QT_HAS_CPP_ATTRIBUTE(fallthrough)
+#  define Q_FALLTHROUGH() [[fallthrough]]
+#elif QT_HAS_CPP_ATTRIBUTE(clang::fallthrough)
+#    define Q_FALLTHROUGH() [[clang::fallthrough]]
+#elif QT_HAS_CPP_ATTRIBUTE(gnu::fallthrough)
+#    define Q_FALLTHROUGH() [[gnu::fallthrough]]
+#endif
+#endif
+#ifndef Q_FALLTHROUGH
+#  if (defined(Q_CC_GNU) && Q_CC_GNU >= 700) && !defined(Q_CC_INTEL)
+#    define Q_FALLTHROUGH() __attribute__((fallthrough))
+#  else
+#    define Q_FALLTHROUGH() (void)0
+#endif
+#endif
+#endif
diff --git a/src/libs/utils/utils-lib.pri b/src/libs/utils/utils-lib.pri
index bfc9d6084e..3a6aa0a09a 100644
--- a/src/libs/utils/utils-lib.pri
+++ b/src/libs/utils/utils-lib.pri
@@ -239,6 +239,7 @@ HEADERS += \
     $$PWD/asconst.h \
     $$PWD/smallstringfwd.h \
     $$PWD/optional.h \
+    $$PWD/qtcfallthrough.h \
     $$PWD/../3rdparty/optional/optional.hpp
 
 FORMS += $$PWD/filewizardpage.ui \
diff --git a/src/libs/utils/utils.qbs b/src/libs/utils/utils.qbs
index 559129df16..6d68683fdd 100644
--- a/src/libs/utils/utils.qbs
+++ b/src/libs/utils/utils.qbs
@@ -175,6 +175,7 @@ Project {
             "proxycredentialsdialog.cpp",
             "proxycredentialsdialog.h",
             "proxycredentialsdialog.ui",
+            "qtcfallthrough.h",
             "qtcassert.cpp",
             "qtcassert.h",
             "qtcolorbutton.cpp",