[REG 5.6->5.7]: Inconsistency with leading zero for double-to-string conversions with a single digit exponent

The code:

const double d = 5.0e-7;
QString str1 = QString::number(d);
QString str2;
QTextStream ts(&str2);
ts << d;
QString str3;
str3.sprintf("%g", d);
qDebug() << str1;
qDebug() << str2;
qDebug() << str3;
QString str4 = QString( "%1" ).arg( d );
qDebug() << str4;

produces this output:

"5e-7"
"5e-07"
"5e-07"
"5e-7"

Obviously, QString::number produces a different string than using a text stream or sprintf. This is inconsistent.

Note, that the behavior of QString::number seems to have been changed/fixed somewhere between version 5.3 and 5.9.1, since when using version 5.3, QString::number produces a leading zero in the exponent as well.

I don't know which is the "correct" way of printing a number. However, I personally would prefer to have as few digits as possible, thus I would choose the first one (produced by QString::number).