Wizards: Support using #pragma once instead of include guards

Allow users to choose #pragma once instead of #ifndef include guards in
generated header files.

Fixes: QTCREATORBUG-12166
Change-Id: I3ba41c7570beb9c5958e174b5581fcc25855050f
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Filip Bucek <fbucek@atlas.cz>

share/qtcreator/templates/qt4project/customwidgetwizard/tpl_collection.h

@@ -1,5 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef @COLLECTION_INCLUDE_GUARD@
 #define @COLLECTION_INCLUDE_GUARD@
+@endif
 
 #include <QtDesigner>
 #include <qplugin.h>
@@ -19,4 +23,6 @@ private:
     QList<QDesignerCustomWidgetInterface*> m_widgets;
 };
 
-#endif
+@if ! '%{Cpp:PragmaOnce}'
+#endif // @COLLECTION_INCLUDE_GUARD@
+@endif

share/qtcreator/templates/qt4project/customwidgetwizard/tpl_single.h

@@ -1,5 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef @SINGLE_INCLUDE_GUARD@
 #define @SINGLE_INCLUDE_GUARD@
+@endif
 
 #include <QDesignerCustomWidgetInterface>
 
@@ -28,4 +32,6 @@ private:
     bool m_initialized;
 };
 
-#endif
+@if ! '%{Cpp:PragmaOnce}'
+#endif // @SINGLE_INCLUDE_GUARD@
+@endif

share/qtcreator/templates/qt4project/customwidgetwizard/tpl_widget.h

@@ -1,5 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef @WIDGET_INCLUDE_GUARD@
 #define @WIDGET_INCLUDE_GUARD@
+@endif
 
 #include <@WIDGET_BASE_CLASS@>
 
@@ -11,4 +15,6 @@ public:
     @WIDGET_CLASS@(QWidget *parent = 0);
 };
 
-#endif
+@if ! '%{Cpp:PragmaOnce}'
+#endif // @WIDGET_INCLUDE_GUARD@
+@endif

share/qtcreator/templates/wizards/autotest/files/tst_src.h

@@ -1,5 +1,10 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
 #pragma once
+@else
+#ifndef %{GUARD}
+#define %{GUARD}
+@endif
 
 #include <gtest/gtest.h>
 #include <gmock/gmock-matchers.h>
@@ -11,3 +16,7 @@ TEST(%{TestCaseName}, %{TestSetName})
     EXPECT_EQ(1, 1);
     ASSERT_THAT(0, Eq(0));
 }
+
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %{GUARD}
+@endif

share/qtcreator/templates/wizards/autotest/wizard.json

@@ -36,6 +36,10 @@
           "key": "TestCaseFileWithHeaderSuffix",
           "value": "%{JS: 'tst_%{TestCaseName}.'.toLowerCase() + Util.preferredSuffix('text/x-c++hdr') }"
         },
+        {
+          "key": "GUARD",
+          "value": "%{JS: '%{TestCaseFileWithHeaderSuffix}'.toUpperCase().replace('.', '_') }"
+        },
         {
           "key": "TestCaseFileWithCppSuffix",
           "value": "%{JS: 'tst_%{TestCaseName}.'.toLowerCase() + Util.preferredSuffix('text/x-c++src') }"

share/qtcreator/templates/wizards/classes/cpp/file.h

@@ -1,6 +1,10 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %{GUARD}
 #define %{GUARD}
+@endif
 
 %{JS: QtSupport.qtIncludes([ ( '%{IncludeQObject}' )          ? 'QtCore/%{IncludeQObject}'                 : '',
                              ( '%{IncludeQWidget}' )          ? 'QtGui/%{IncludeQWidget}'                  : '',
@@ -53,4 +57,6 @@ private:
 @endif
 };
 %{JS: Cpp.closeNamespaces('%{Class}')}
-#endif // %{GUARD}\
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %{GUARD}
+@endif

share/qtcreator/templates/wizards/classes/itemmodel/itemmodel.h

@@ -1,6 +1,10 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %{GUARD}
 #define %{GUARD}
+@endif
 
 %{JS: QtSupport.qtIncludes([ 'QtCore/%{Base}' ], [ 'QtCore/%{Base}' ])}\
 %{JS: Cpp.openNamespaces('%{Class}')}\
@@ -62,4 +66,6 @@ public:
 private:
 };
 %{JS: Cpp.closeNamespaces('%{Class}')}
-#endif // %{GUARD}\
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %{GUARD}
+@endif

share/qtcreator/templates/wizards/classes/itemmodel/listmodel.h

@@ -1,6 +1,10 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %{GUARD}
 #define %{GUARD}
+@endif
 
 %{JS: QtSupport.qtIncludes([ 'QtCore/%{Base}' ], [ 'QtCore/%{Base}' ])}\
 %{JS: Cpp.openNamespaces('%{Class}')}\
@@ -47,4 +51,6 @@ public:
 private:
 };
 %{JS: Cpp.closeNamespaces('%{Class}')}
-#endif // %{GUARD}\
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %{GUARD}
+@endif

share/qtcreator/templates/wizards/classes/itemmodel/tablemodel.h

@@ -1,6 +1,10 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %{GUARD}
 #define %{GUARD}
+@endif
 
 %{JS: QtSupport.qtIncludes([ 'QtCore/%{Base}' ], [ 'QtCore/%{Base}' ])}\
 %{JS: Cpp.openNamespaces('%{Class}')}\
@@ -50,4 +54,6 @@ public:
 private:
 };
 %{JS: Cpp.closeNamespaces('%{Class}')}
-#endif // %{GUARD}\
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %{GUARD}
+@endif

share/qtcreator/templates/wizards/files/cppheader/file.h

@@ -1,5 +1,9 @@
 %{Cpp:LicenseTemplate}\
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %{JS: Cpp.headerGuard('%{FileName}')}
 #define %{JS: Cpp.headerGuard('%{FileName}')}
 
 #endif // %{JS: Cpp.headerGuard('%{FileName}')}
+@endif

share/qtcreator/templates/wizards/qtcreatorplugin/myplugin.h

@@ -1,4 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
 #pragma once
+@else
+#ifndef %ProjectName:h%_H
+#define %ProjectName:h%_H
+@endif
 
 #include "%PluginName:l%_global.%CppHeaderSuffix%"
 
@@ -26,3 +31,7 @@ private:
 
 } // namespace Internal
 } // namespace %PluginName%
+
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %ProjectName:h%_H
+@endif

share/qtcreator/templates/wizards/qtcreatorplugin/myplugin_global.h

@@ -1,4 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
 #pragma once
+@else
+#ifndef %ProjectName:h%_GLOBAL_H
+#define %ProjectName:h%_GLOBAL_H
+@endif
 
 #include <QtGlobal>
 
@@ -7,3 +12,7 @@
 #else
 #  define %PluginName:u%SHARED_EXPORT Q_DECL_IMPORT
 #endif
+
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %ProjectName:h%_GLOBAL_H
+@endif

share/qtcreator/templates/wizards/qtcreatorplugin/mypluginconstants.h

@@ -1,4 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
 #pragma once
+@else
+#ifndef %ProjectName:h%_CONSTANTS_H
+#define %ProjectName:h%_CONSTANTS_H
+@endif
 
 namespace %PluginName% {
 namespace Constants {
@@ -8,3 +13,7 @@ const char MENU_ID[] = "%PluginName%.Menu";
 
 } // namespace %PluginName%
 } // namespace Constants
+
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %ProjectName:h%_CONSTANTS_H
+@endif

share/qtcreator/templates/wizards/qtquick2-extension/object.h

@@ -1,5 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
+#pragma once
+@else
 #ifndef %ObjectName:u%_H
 #define %ObjectName:u%_H
+@endif
 
 #include <QQuickItem>
 
@@ -13,4 +17,6 @@ public:
     ~%ObjectName%();
 };
 
+@if ! '%{Cpp:PragmaOnce}'
 #endif // %ObjectName:u%_H
+@endif

share/qtcreator/templates/wizards/qtquick2-extension/plugin.h

@@ -1,4 +1,9 @@
+@if '%{Cpp:PragmaOnce}'
 #pragma once
+@else
+#ifndef %ProjectName:h%_PLUGIN_H
+#define %ProjectName:h%_PLUGIN_H
+@endif
 
 #include <QQmlExtensionPlugin>
 
@@ -10,3 +15,7 @@ class %ProjectName:s%Plugin : public QQmlExtensionPlugin
 public:
     void registerTypes(const char *uri) override;
 };
+
+@if ! '%{Cpp:PragmaOnce}'
+#endif // %ProjectName:h%_PLUGIN_H
+@endif

src/plugins/cpptools/abstracteditorsupport.cpp

@@ -27,6 +27,7 @@
 
 #include "cppfilesettingspage.h"
 #include "cppmodelmanager.h"
+#include "cpptools/cpptoolsplugin.h"
 
 #include <utils/fileutils.h>
 #include <utils/macroexpander.h>
@@ -68,5 +69,10 @@ QString AbstractEditorSupport::licenseTemplate(const QString &file, const QStrin
     return Utils::TemplateEngine::processText(&expander, license, nullptr);
 }
 
+bool AbstractEditorSupport::usePragmaOnce()
+{
+    return Internal::CppToolsPlugin::instance()->usePragmaOnce();
+}
+
 } // namespace CppTools
 

src/plugins/cpptools/abstracteditorsupport.h

@@ -49,6 +49,7 @@ public:
     unsigned revision() const { return m_revision; }
 
     static QString licenseTemplate(const QString &file = QString(), const QString &className = QString());
+    static bool usePragmaOnce();
 
 private:
     CppModelManager *m_modelmanager;

src/plugins/cpptools/cppfilesettingspage.cpp

@@ -55,6 +55,7 @@ static const char headerSuffixKeyC[] = "HeaderSuffix";
 static const char sourceSuffixKeyC[] = "SourceSuffix";
 static const char headerSearchPathsKeyC[] = "HeaderSearchPaths";
 static const char sourceSearchPathsKeyC[] = "SourceSearchPaths";
+static const char headerPragmaOnceC[] = "HeaderPragmaOnce";
 static const char licenseTemplatePathKeyC[] = "LicenseTemplate";
 
 const char *licenseTemplateTemplate = QT_TRANSLATE_NOOP("CppTools::Internal::CppFileSettingsWidget",
@@ -68,11 +69,6 @@ const char *licenseTemplateTemplate = QT_TRANSLATE_NOOP("CppTools::Internal::Cpp
 namespace CppTools {
 namespace Internal {
 
-CppFileSettings::CppFileSettings() :
-    lowerCaseFiles(false)
-{
-}
-
 void CppFileSettings::toSettings(QSettings *s) const
 {
     s->beginGroup(QLatin1String(Constants::CPPTOOLS_SETTINGSGROUP));
@@ -83,6 +79,7 @@ void CppFileSettings::toSettings(QSettings *s) const
     s->setValue(QLatin1String(headerSearchPathsKeyC), headerSearchPaths);
     s->setValue(QLatin1String(sourceSearchPathsKeyC), sourceSearchPaths);
     s->setValue(QLatin1String(Constants::LOWERCASE_CPPFILES_KEY), lowerCaseFiles);
+    s->setValue(QLatin1String(headerPragmaOnceC), headerPragmaOnce);
     s->setValue(QLatin1String(licenseTemplatePathKeyC), licenseTemplatePath);
     s->endGroup();
 }
@@ -106,6 +103,7 @@ void CppFileSettings::fromSettings(QSettings *s)
             .toStringList();
     const bool lowerCaseDefault = Constants::lowerCaseFilesDefault;
     lowerCaseFiles = s->value(QLatin1String(Constants::LOWERCASE_CPPFILES_KEY), QVariant(lowerCaseDefault)).toBool();
+    headerPragmaOnce = s->value(headerPragmaOnceC, headerPragmaOnce).toBool();
     licenseTemplatePath = s->value(QLatin1String(licenseTemplatePathKeyC), QString()).toString();
     s->endGroup();
 }
@@ -127,6 +125,7 @@ bool CppFileSettings::applySuffixesToMimeDB()
 bool CppFileSettings::equals(const CppFileSettings &rhs) const
 {
     return lowerCaseFiles == rhs.lowerCaseFiles
+           && headerPragmaOnce == rhs.headerPragmaOnce
            && headerPrefixes == rhs.headerPrefixes
            && sourcePrefixes == rhs.sourcePrefixes
            && headerSuffix == rhs.headerSuffix
@@ -303,6 +302,7 @@ CppFileSettings CppFileSettingsWidget::settings() const
 {
     CppFileSettings rc;
     rc.lowerCaseFiles = m_ui->lowerCaseFileNamesCheckBox->isChecked();
+    rc.headerPragmaOnce = m_ui->headerPragmaOnceCheckBox->isChecked();
     rc.headerPrefixes = trimmedPaths(m_ui->headerPrefixesEdit->text());
     rc.sourcePrefixes = trimmedPaths(m_ui->sourcePrefixesEdit->text());
     rc.headerSuffix = m_ui->headerSuffixComboBox->currentText();
@@ -323,6 +323,7 @@ void CppFileSettingsWidget::setSettings(const CppFileSettings &s)
 {
     const QChar comma = QLatin1Char(',');
     m_ui->lowerCaseFileNamesCheckBox->setChecked(s.lowerCaseFiles);
+    m_ui->headerPragmaOnceCheckBox->setChecked(s.headerPragmaOnce);
     m_ui->headerPrefixesEdit->setText(s.headerPrefixes.join(comma));
     m_ui->sourcePrefixesEdit->setText(s.sourcePrefixes.join(comma));
     setComboText(m_ui->headerSuffixComboBox, s.headerSuffix);

src/plugins/cpptools/cppfilesettingspage.h

@@ -42,16 +42,15 @@ namespace Ui { class CppFileSettingsPage; }
 
 struct CppFileSettings
 {
-    CppFileSettings();
-
     QStringList headerPrefixes;
     QString headerSuffix;
     QStringList headerSearchPaths;
     QStringList sourcePrefixes;
     QString sourceSuffix;
     QStringList sourceSearchPaths;
-    bool lowerCaseFiles;
     QString licenseTemplatePath;
+    bool headerPragmaOnce = false;
+    bool lowerCaseFiles = false;
 
     void toSettings(QSettings *) const;
     void fromSettings(QSettings *);

src/plugins/cpptools/cppfilesettingspage.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>547</width>
-    <height>363</height>
+    <height>406</height>
    </rect>
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
@@ -67,7 +67,7 @@ These paths are used in addition to current directory on Switch Header/Source.</
         </property>
        </widget>
       </item>
-      <item row="4" column="0">
+      <item row="5" column="0">
        <widget class="QLabel" name="headerPrefixesLabel">
         <property name="text">
          <string>&amp;Prefixes:</string>
@@ -77,7 +77,7 @@ These paths are used in addition to current directory on Switch Header/Source.</
         </property>
        </widget>
       </item>
-      <item row="4" column="1">
+      <item row="5" column="1">
        <widget class="QLineEdit" name="headerPrefixesEdit">
         <property name="toolTip">
          <string>Comma-separated list of header prefixes.
@@ -86,6 +86,26 @@ These prefixes are used in addition to current file name on Switch Header/Source
         </property>
        </widget>
       </item>
+      <item row="7" column="0">
+       <widget class="QLabel" name="headerPragmaOnceLabel">
+        <property name="toolTip">
+         <string/>
+        </property>
+        <property name="text">
+         <string>Include guards</string>
+        </property>
+       </widget>
+      </item>
+      <item row="7" column="1">
+       <widget class="QCheckBox" name="headerPragmaOnceCheckBox">
+        <property name="toolTip">
+         <string>Uses #pragma once instead of #ifndef include guards.</string>
+        </property>
+        <property name="text">
+         <string>Use '#pragma once' instead of '#ifndef' guards</string>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>

src/plugins/cpptools/cpptoolsplugin.cpp

@@ -140,6 +140,11 @@ QString CppToolsPlugin::licenseTemplate()
     return m_instance->m_fileSettings->licenseTemplate();
 }
 
+bool CppToolsPlugin::usePragmaOnce()
+{
+    return m_instance->m_fileSettings->headerPragmaOnce;
+}
+
 const QStringList &CppToolsPlugin::headerSearchPaths()
 {
     return m_instance->m_fileSettings->headerSearchPaths;
@@ -204,6 +209,11 @@ bool CppToolsPlugin::initialize(const QStringList &arguments, QString *error)
                                     tr("The configured path to the license template"),
                                     []() { return CppToolsPlugin::licenseTemplatePath().toString(); });
 
+    expander->registerVariable(
+                "Cpp:PragmaOnce",
+                tr("Insert #pragma once instead of #ifndef include guards into header file"),
+                [] { return usePragmaOnce() ? QString("true") : QString(); });
+
     return true;
 }
 

src/plugins/cpptools/cpptoolsplugin.h

@@ -65,6 +65,7 @@ public:
     static void clearHeaderSourceCache();
     static Utils::FileName licenseTemplatePath();
     static QString licenseTemplate();
+    static bool usePragmaOnce();
 
     bool initialize(const QStringList &arguments, QString *errorMessage) final;
     void extensionsInitialized() final;

src/plugins/designer/cpp/formclasswizarddialog.cpp

@@ -26,6 +26,7 @@
 #include "formclasswizarddialog.h"
 #include "formclasswizardpage.h"
 #include "formclasswizardparameters.h"
+#include <cpptools/abstracteditorsupport.h>
 #include <designer/formtemplatewizardpage.h>
 #include <qtsupport/codegenerator.h>
 
@@ -88,6 +89,7 @@ FormClassWizardParameters FormClassWizardDialog::parameters() const
     m_classPage->getParameters(&rc);
     // Name the ui class in the Ui namespace after the class specified
     rc.uiTemplate = QtSupport::CodeGenerator::changeUiClassName(m_rawFormTemplate, rc.className);
+    rc.usePragmaOnce = CppTools::AbstractEditorSupport::usePragmaOnce();
     return rc;
 }
 

src/plugins/designer/cpp/formclasswizardparameters.h

@@ -43,6 +43,7 @@ public:
     QString sourceFile;
     QString headerFile;
     QString uiFile;
+    bool usePragmaOnce = false;
 };
 } // namespace Designer
 

src/plugins/designer/qtdesignerformclasscodegenerator.cpp

@@ -104,8 +104,12 @@ bool QtDesignerFormClassCodeGenerator::generateCpp(const FormClassWizardParamete
 
     // 1) Header file
     QTextStream headerStr(header);
-    headerStr << headerLicense << "#ifndef " << guard
+    headerStr << headerLicense;
-              << "\n#define " <<  guard << '\n' << '\n';
+
+    if (parameters.usePragmaOnce)
+        headerStr << "#pragma once\n\n";
+    else
+        headerStr << "#ifndef " << guard << "\n#define " << guard << "\n\n";
 
     // Include 'ui_'
     if (generationParameters.embedding != QtSupport::CodeGenSettings::PointerAggregatedUiClass) {
@@ -165,7 +169,9 @@ bool QtDesignerFormClassCodeGenerator::generateCpp(const FormClassWizardParamete
     }
     headerStr << namespaceIndent << "};\n\n";
     Utils::writeClosingNameSpaces(namespaceList, QString(), headerStr);
-    headerStr << "#endif // "<<  guard << '\n';
+
+    if (!parameters.usePragmaOnce)
+        headerStr << "#endif // " << guard << '\n';
 
     // 2) Source file
     QTextStream sourceStr(source);

src/plugins/projectexplorer/customwizard/customwizardparameters.cpp

@@ -939,7 +939,17 @@ QString CustomWizardContext::processFile(const FieldReplacementMap &fm, QString
         replaceFields(fm, &in);
 
     QString out;
+
+    // Expander needed to handle extra variable "Cpp:PragmaOnce"
     QString errorMessage;
+    Utils::MacroExpander *expander = Utils::globalMacroExpander();
+    in = Utils::TemplateEngine::processText(expander, in, &errorMessage);
+    if (!errorMessage.isEmpty()) {
+        qWarning("Error processing custom widget file: %s\nFile:\n%s",
+                 qPrintable(errorMessage), qPrintable(in));
+        return QString();
+    }
+
     if (!Utils::TemplateEngine::preprocessText(in, &out, &errorMessage)) {
         qWarning("Error preprocessing custom widget file: %s\nFile:\n%s",
                  qPrintable(errorMessage), qPrintable(in));

src/plugins/qmakeprojectmanager/customwidgetwizard/plugingenerator.cpp

@@ -30,6 +30,8 @@
 #include <cpptools/abstracteditorsupport.h>
 
 #include <utils/fileutils.h>
+#include <utils/macroexpander.h>
+#include <utils/templateengine.h>
 
 #include <QFileInfo>
 #include <QDir>
@@ -311,7 +313,20 @@ QString PluginGenerator::processTemplate(const QString &tmpl,
     if (!reader.fetch(tmpl, errorMessage))
         return QString();
 
+
     QString cont = QString::fromUtf8(reader.data());
+
+    // Expander needed to handle extra variable "Cpp:PragmaOnce"
+    Utils::MacroExpander *expander = Utils::globalMacroExpander();
+    QString errMsg;
+    cont = Utils::TemplateEngine::processText(expander, cont, &errMsg);
+    if (!errMsg.isEmpty()) {
+        qWarning("Error processing custom plugin file: %s\nFile:\n%s",
+                 qPrintable(errMsg), qPrintable(cont));
+        errorMessage = &errMsg;
+        return QString();
+    }
+
     const QChar atChar = QLatin1Char('@');
     int offset = 0;
     for (;;) {

src/plugins/qmakeprojectmanager/wizards/guiappwizard.cpp

@@ -105,6 +105,7 @@ static inline bool generateFormClass(const GuiAppParameters &params,
     fp.className = params.className;
     fp.sourceFile = params.sourceFileName;
     fp.headerFile = params.headerFileName;
+    fp.usePragmaOnce = CppTools::AbstractEditorSupport::usePragmaOnce();
     QString headerContents;
     QString sourceContents;
     // Invoke code generation service of Qt Designer plugin.
@@ -224,7 +225,6 @@ bool GuiAppWizard::parametrizeTemplate(const QString &templatePath, const QStrin
     if (!reader.fetch(fileName, QIODevice::Text, errorMessage))
         return false;
     QString contents = QString::fromUtf8(reader.data());
-
     contents.replace(QLatin1String("%QAPP_INCLUDE%"), QLatin1String("QApplication"));
     contents.replace(QLatin1String("%INCLUDE%"), params.headerFileName);
     contents.replace(QLatin1String("%CLASS%"), params.className);
@@ -236,6 +236,11 @@ bool GuiAppWizard::parametrizeTemplate(const QString &templatePath, const QStrin
     else
         contents.replace(QLatin1String("%SHOWMETHOD%"), QString::fromLatin1(mainSourceShowC));
 
+    // Replace include guards with pragma once
+    if (CppTools::AbstractEditorSupport::usePragmaOnce()) {
+        contents.replace(QLatin1String("#ifndef %PRE_DEF%\n#define %PRE_DEF%"), "#pragma once");
+        contents.replace(QLatin1String("#endif // %PRE_DEF%\n"), QString());
+    }
 
     const QChar dot = QLatin1Char('.');
 

src/plugins/qmakeprojectmanager/wizards/libraryparameters.cpp

@@ -31,25 +31,6 @@
 #include <QTextStream>
 #include <QStringList>
 
-// Contents of the header defining the shared library export.
-#define GUARD_VARIABLE "<GUARD>"
-#define EXPORT_MACRO_VARIABLE "<EXPORT_MACRO>"
-#define LIBRARY_MACRO_VARIABLE "<LIBRARY_MACRO>"
-
-static const char *globalHeaderContentsC =
-"#ifndef " GUARD_VARIABLE "\n"
-"#define " GUARD_VARIABLE "\n"
-"\n"
-"#include <QtCore/qglobal.h>\n"
-"\n"
-"#if defined(" LIBRARY_MACRO_VARIABLE ")\n"
-"#  define " EXPORT_MACRO_VARIABLE " Q_DECL_EXPORT\n"
-"#else\n"
-"#  define " EXPORT_MACRO_VARIABLE " Q_DECL_IMPORT\n"
-"#endif\n"
-"\n"
-"#endif // " GUARD_VARIABLE "\n";
-
 namespace QmakeProjectManager {
 namespace Internal {
 
@@ -60,6 +41,7 @@ void LibraryParameters::generateCode(QtProjectParameters:: Type t,
                                      const QString &exportMacro,
                                      const QString &pluginJsonFileName,
                                      int indentation,
+                                     bool usePragmaOnce,
                                      QString *header,
                                      QString *source) const
 {
@@ -76,8 +58,10 @@ void LibraryParameters::generateCode(QtProjectParameters:: Type t,
 
     // 1) Header
     const QString guard = Utils::headerGuard(headerFileName, namespaceList);
-    headerStr << "#ifndef " << guard
+    if (usePragmaOnce)
-        << "\n#define " <<  guard << '\n' << '\n';
+        headerStr << "#pragma once\n\n";
+    else
+        headerStr << "#ifndef " << guard << "\n#define " << guard << "\n\n";
 
     if (!sharedHeader.isEmpty())
         Utils::writeIncludeFileDirective(sharedHeader, false, headerStr);
@@ -123,7 +107,9 @@ void LibraryParameters::generateCode(QtProjectParameters:: Type t,
         headerStr << namespaceIndent << indent << unqualifiedClassName << "();\n";
     headerStr << namespaceIndent << "};\n\n";
     Utils::writeClosingNameSpaces(namespaceList, indent, headerStr);
-    headerStr <<  "#endif // "<<  guard << '\n';
+    if (!usePragmaOnce)
+        headerStr <<  "#endif // " << guard << '\n';
+
     /// 2) Source
     QTextStream sourceStr(source);
 
@@ -152,12 +138,28 @@ void LibraryParameters::generateCode(QtProjectParameters:: Type t,
 
 QString  LibraryParameters::generateSharedHeader(const QString &globalHeaderFileName,
                                                  const QString &projectTarget,
-                                                 const QString &exportMacro)
+                                                 const QString &exportMacro,
+                                                 bool usePragmaOnce)
 {
-    QString contents = QLatin1String(globalHeaderContentsC);
+    QString contents;
-    contents.replace(QLatin1String(GUARD_VARIABLE), Utils::headerGuard(globalHeaderFileName));
+    if (usePragmaOnce) {
-    contents.replace(QLatin1String(EXPORT_MACRO_VARIABLE), exportMacro);
+        contents += "#pragma once\n";
-    contents.replace(QLatin1String(LIBRARY_MACRO_VARIABLE), QtProjectParameters::libraryMacro(projectTarget));
+    } else {
+        contents += "#ifndef " + Utils::headerGuard(globalHeaderFileName) + "\n";
+        contents += "#define " + Utils::headerGuard(globalHeaderFileName) + "\n";
+    }
+    contents += "\n";
+    contents += "#include <QtCore/qglobal.h>\n";
+    contents += "\n";
+    contents += "#if defined(" + QtProjectParameters::libraryMacro(projectTarget) + ")\n";
+    contents += "#  define " + exportMacro + " Q_DECL_EXPORT\n";
+    contents += "#else\n";
+    contents += "#  define " + exportMacro + " Q_DECL_IMPORT\n";
+    contents += "#endif\n";
+    contents += "\n";
+    if (!usePragmaOnce)
+        contents += "#endif // " + Utils::headerGuard(globalHeaderFileName) + '\n';
+
     return contents;
 }
 

src/plugins/qmakeprojectmanager/wizards/libraryparameters.h

@@ -44,13 +44,15 @@ struct LibraryParameters {
                       const QString &exportMacro,
                       const QString &pluginJsonFileName,
                       int indentation,
+                      bool usePragmaOnce,
                       QString *header,
                       QString *source) const;
 
     // Generate the code of the shared header containing the export macro
     static QString generateSharedHeader(const QString &globalHeaderFileName,
                                         const QString &projectTarget,
-                                        const QString &exportMacro);
+                                        const QString &exportMacro,
+                                        bool usePragmaOnce);
 
     QString className;
     QString baseClassName;

src/plugins/qmakeprojectmanager/wizards/librarywizard.cpp

@@ -80,6 +80,7 @@ Core::GeneratedFiles LibraryWizard::generateFiles(const QWizard *w,
     const QtProjectParameters projectParams = dialog->parameters();
     const QString projectPath = projectParams.projectPath();
     const LibraryParameters params = dialog->libraryParameters();
+    const bool usePragmaOnce = CppTools::AbstractEditorSupport::usePragmaOnce();
 
     const QString sharedLibExportMacro = QtProjectParameters::exportMacro(projectParams.fileName);
 
@@ -107,7 +108,7 @@ Core::GeneratedFiles LibraryWizard::generateFiles(const QWizard *w,
         Core::GeneratedFile globalHeader(globalHeaderName);
         globalHeaderFileName = Utils::FileName::fromString(globalHeader.path()).fileName();
         globalHeader.setContents(CppTools::AbstractEditorSupport::licenseTemplate(globalHeaderFileName)
-                                 + LibraryParameters::generateSharedHeader(globalHeaderFileName, projectParams.fileName, sharedLibExportMacro));
+                                 + LibraryParameters::generateSharedHeader(globalHeaderFileName, projectParams.fileName, sharedLibExportMacro, usePragmaOnce));
         rc.push_back(globalHeader);
     }
 
@@ -115,7 +116,7 @@ Core::GeneratedFiles LibraryWizard::generateFiles(const QWizard *w,
     QString headerContents, sourceContents;
     params.generateCode(projectParams.type, projectParams.fileName,  headerFileName,
                         globalHeaderFileName, sharedLibExportMacro, pluginJsonFileName,
-                        /* indentation*/ 4, &headerContents, &sourceContents);
+                        /* indentation*/ 4, usePragmaOnce, &headerContents, &sourceContents);
 
     source.setContents(CppTools::AbstractEditorSupport::licenseTemplate(sourceFileName, params.className)
                        + sourceContents);