Perhaps I did a big error but I have a very strange problem
with the xterm last version (size 3617 bytes)

With the program as attachment I read a and display a file containing

linbase
=======

The program shows :

linbase
=

The output with fprintf on stderr is ok :


Note : I have not this problem with term=linux and old xterm (ncurses-6.0)

Context
=======
Slackware 14.2 x86_64 with updates
Texlive 2017-171108
kde-4