xsel output contains trash at the end if a long input is piped into it to set the clipboard

Question

To reproduce:

seq 10000 | /usr/bin/xsel -b
/usr/bin/xsel -b

Observed output: either of:

• nothing
• the correct output
• the correct output + a few lines of trash at the end

The output changes randomly between those three even if I run xsel -b multiple times without resetting it with the pipe to stdin!

The input has to be large enough: seq 1000 does not work. The actual bytes don't seem to matter, only the input size.

Once I do seq 10000 | /usr/bin/xsel -b:

• xclip -selection clipboard -o is also corrupted, but in a different weird way
• pasting with Ctrl + V on a textarea seems to work normally

I do not reproduce this if I try to set the textarea with:

• Ctrl + C
• seq 10000 | xclip -selection clipboard

so it seems to be a problem in the way xsel handles the stdin input.

Using -i and -o did not change anything.

The problem started today "by itself".

If you reproduce, please add a comment below.

Ubuntu 14.04 AMD64, xsel 1.2.0.