---- On Thu, 28 Mar 2019 18:53:41 +0100 Hans Hagen <j.hagen@xs4all.nl> wrote ----
 > On 3/28/2019 3:57 PM, Marcel Krüger wrote:
 > > Hi,
 > >
 > > there are multiple issues memory issues in tprint:
 > >
 > > If the buffer passed to tprint only contains of to be escaped characters, the `xmalloc(strlen(sss)*3)` is too small: The final `\0` can not be written, so this causes a write into unallocated memory.
 > > If t_flush_buffer is called for such a buffer at the last position, there is an additional `\n` written, so `xmalloc(strlen(sss)*3+2)` is needed.
 > >
 > > Additionally, the test `if (*buffer)` is used to test if there is something to print left. If the parameter is empty, `*buffer` is never written, so valgrind complains about `if (*buffer)` depending on uninitialized memory. Instead, `if (i)` can be used: `i` is the length of the written part of the buffer, so `i==0` iff there is nothing to write.
 > >
 > > A related problem is with `max_print_line`:
 > > If the point where the line should be broken falls inside the escape sequence of an escaped character,
 > > the line limit is ignored.
 > > This can be fixed by adding
 > >
 > >          if (term_offset+2>=max_print_line) {
 > >              wterm_cr();
 > >              term_offset=0;
 > >          }
 > >
 > > as in `wterm_char` also in tprint above `buffer[i++] = '^';`.
 > >
 > > A full patch fixing all three issues is attached.
 > Can you give a plain tex example where the fault happens? Normally the
 > max line length kicks in (3 chars) before such an overflow.

Try

\let\3\relax
\directlua{
  texio.write'\3'% Only to be escaped characters -> valgrind complains about write into unallocated memory

  texio.write_nl''

  for i=1,kpse.var_value'max_print_line'-3 do texio.write'.' end
  texio.write'\3' % Here LuaTex writes 2 and not just 1 byte after it's allocated memory area

  for i=1,kpse.var_value'max_print_line'-1 do texio.write'.' end
  texio.write'\3' % The line break would fall inside of the escape sequence -> Line limit ignored
  for i=1,2*kpse.var_value'max_print_line' do texio.write'.' end % This should normally not fit into one line
}
\bye