Bug 362197

This can be reproduced with the following bash command:

i=0; while true; do echo "$i $i $i $i $i $i $i $i $i $i $i" >&2; i=$((i+1)); done

Once the numbers printed grow larger than about 2.1 million, Konsole starts repeatedly printing a message to its parent terminal:

HistoryFile::add.seek: Invalid argument

And if you try to scroll back, you'll see empty lines right above the first visible line. If you scroll more back, you'll get to the last line which has successfully been appended to the scrollback buffer. Saving the scrollback also gives this result, i.e. lines between the last screen and last successful scrollback update are completely empty.

Reproducible: Always

Steps to Reproduce:
0. Set scrollback to Unlimited in Konsole settings
1. Run Konsole (from another terminal to see its stderr)
2. Run this command in bash inside Konsole session:
i=0; while true; do echo "$i $i $i $i $i $i $i $i $i $i $i" >&2; i=$((i+1)); done
3. Wait until numbers printed grow larger than about 2.1 million
4. Try to scroll back

Actual Results:  
Nearest scrollback lines get lost

Expected Results:  
The complete scrollback buffer should be saved correctly

This happens both in KDE 4.14 and KF5.