PERF: Don't create temporary QRegularExpression

warning: Don't create temporary QRegularExpression objects. Use a
static QRegularExpression object instead [-Wclazy-use-static-qregularexpression]

Is alerting that the same QRegularExpression object is re-created
every time a function is called or expression is evaluated. This is
inefficient, especially for repeated use, because QRegularExpression has
a non-trivial construction cost (it compiles the regex pattern).

auto match = re.match(content);

Author: hjmjohnson

generator/main.cpp

@@ -223,7 +223,8 @@ namespace
 
     unsigned int getQtVersion(const QString &commandLineIncludes, const QString &qtIncludPrefix = {})
     {
-      QRegularExpression re("#define\\s+QTCORE_VERSION\\s+0x([0-9a-f]+)", QRegularExpression::CaseInsensitiveOption);
+      static const QRegularExpression re("#define\\s+QTCORE_VERSION\\s+0x([0-9a-f]+)",
+        QRegularExpression::CaseInsensitiveOption);
       for (const QString &includeDir: getIncludeDirectories(commandLineIncludes, qtIncludPrefix))
       {
         QFileInfo fi(QDir(includeDir), "qtcoreversion.h");