CompilationDatabase: Force QString implicit sharing

Most of the flags in compilation database are the same,
let's share them by inserting them all into the temporary
QSet of QString-s.

Change-Id: I7d9b410b4b0bee40247434b49371bd37214d4c59
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp

@@ -64,16 +64,18 @@ namespace Internal {
 
 namespace {
 
-QStringList jsonObjectFlags(const QJsonObject &object)
+QStringList jsonObjectFlags(const QJsonObject &object, QSet<QString> &flagsCache)
 {
     QStringList flags;
     const QJsonArray arguments = object["arguments"].toArray();
     if (arguments.isEmpty()) {
-        flags = splitCommandLine(object["command"].toString());
+        flags = splitCommandLine(object["command"].toString(), flagsCache);
     } else {
         flags.reserve(arguments.size());
-        for (const QJsonValue &arg : arguments)
-            flags.append(arg.toString());
+        for (const QJsonValue &arg : arguments) {
+            auto flagIt = flagsCache.insert(arg.toString());
+            flags.append(*flagIt);
+        }
     }
 
     return flags;
@@ -339,6 +341,7 @@ std::vector<Entry> readJsonObjects(const QString &filePath)
     int objectStart = contents.indexOf('{');
     int objectEnd = contents.indexOf('}', objectStart + 1);
 
+    QSet<QString> flagsCache;
     while (objectStart >= 0 && objectEnd >= 0) {
         const QJsonDocument document = QJsonDocument::fromJson(
                     contents.mid(objectStart, objectEnd - objectStart + 1));
@@ -350,8 +353,8 @@ std::vector<Entry> readJsonObjects(const QString &filePath)
 
         const QJsonObject object = document.object();
         const Utils::FileName fileName = jsonObjectFilename(object);
-        const QStringList flags
-                = filterFromFileName(jsonObjectFlags(object), fileName.toFileInfo().baseName());
+        const QStringList flags = filterFromFileName(jsonObjectFlags(object, flagsCache),
+                                                     fileName.toFileInfo().baseName());
         result.push_back({flags, fileName, object["directory"].toString()});
 
         objectStart = contents.indexOf('{', objectEnd + 1);

src/plugins/compilationdatabaseprojectmanager/compilationdatabaseutils.cpp

@@ -33,6 +33,7 @@
 
 #include <QDir>
 #include <QRegularExpression>
+#include <QSet>
 
 using namespace ProjectExplorer;
 
@@ -205,7 +206,7 @@ void filteredFlags(const QString &fileName,
     flags = filtered;
 }
 
-QStringList splitCommandLine(QString commandLine)
+QStringList splitCommandLine(QString commandLine, QSet<QString> &flagsCache)
 {
     QStringList result;
     bool insideQuotes = false;
@@ -215,12 +216,19 @@ QStringList splitCommandLine(QString commandLine)
     for (const QString &part : commandLine.split(QRegularExpression("\""))) {
         if (insideQuotes) {
             const QString quotedPart = "\"" + part + "\"";
-            if (result.last().endsWith("="))
-                result.last().append(quotedPart);
-            else
-                result.append(quotedPart);
+            if (result.last().endsWith("=")) {
+                auto flagIt = flagsCache.insert(result.last() + quotedPart);
+                result.last() = *flagIt;
+            } else {
+                auto flagIt = flagsCache.insert(quotedPart);
+                result.append(*flagIt);
+            }
         } else { // If 's' is outside quotes ...
-            result.append(part.split(QRegularExpression("\\s+"), QString::SkipEmptyParts));
+            for (const QString &flag :
+                 part.split(QRegularExpression("\\s+"), QString::SkipEmptyParts)) {
+                auto flagIt = flagsCache.insert(flag);
+                result.append(*flagIt);
+            }
         }
         insideQuotes = !insideQuotes;
     }

src/plugins/compilationdatabaseprojectmanager/compilationdatabaseutils.h

@@ -47,6 +47,6 @@ void filteredFlags(const QString &fileName,
                    QVector<ProjectExplorer::Macro> &macros,
                    CppTools::ProjectFile::Kind &fileKind);
 
-QStringList splitCommandLine(QString commandLine);
+QStringList splitCommandLine(QString commandLine, QSet<QString> &flagsCache);
 
 } // namespace CompilationDatabaseProjectManager