During termination my program causes access violation trying to read at nullptr when I call

QTextStream(stdout) << ... << endl;

from within my global object's destructor.

The problem is here:

void QTextStreamPrivate::flushWriteBuffer()
{
...
if (!codec)}}
codec = QTextCodec::codecForLocale();

Since here you just assume codec is not nullptr and access it like this:

QByteArray data = codec->fromUnicode(writeBuffer.data(), writeBuffer.size(), &writeConverterState);

but QTextCodec::codecForLocale() may have returned nullptr if some internal Qt global data is already destroyed (destroyed before my global object) and if this is the case codec stays nullptr.