QObject::inherits() returns false if passed classname of current class on some compilers

On some compilers QObject::inherits() in Qt 6.7.0 fails to return true when passing the classname of the current class.

A simplified example that reproduces this:

#include <QCoreApplication>
#include <QDebug>
#include <QObject>

class MyObject : public QObject {
  Q_OBJECT
public:
MyObject() : QObject(nullptr) {
  qDebug() << inherits("MyObject") << inherits("QObject");
}
};

int main(int argc, char **argv) {
  QCoreApplication app(argc, argv);
  MyObject mo;
  return 0;
}

#include "moc_qobjectinherits.cpp"

The above example was built and then executed on the following Linux x86_64 systems:

• Qt 6.6.0 + CentOS 8 + gcc-devtoolset-9 (gcc 9.2.1)
• Qt 6.7.0 + CentOS 8 + gcc-devtoolset-9 (gcc 9.2.1)
• Qt 6.7.0 + Ubuntu 22.04 (gcc 11.4.0)

Expected output is true true but with Qt 6.7.0 and gcc 9.2.1 it is false true.

A bit of debugging by modifying the generated MyObject::qt_metacast() moc code shows that the problematic compiler seems to "omit" the nul-terminator in the generated stringdata. When trying to print that out via qDebug("%s", qt_meta_stringdata_CLASSMyObjectENDCLASS.stringdata0) that gcc prints warning: ‘%s’ directive argument is not a nul-terminated string.
In comparison, gcc 11.4.0 on Ubuntu shows no warning for the same statement.

This is problematic for Squish (see SQUISH-17447) which requires this inherits check for finding objects via their classname (plus other property values).