Re: Strange ncurses bug with getch() and window resize?

[Thomas Dickey]

On Fri, 4 Aug 2006, Simon Stelling wrote:

> I'm writing a tool that uses ncurses to draw. When the xterm window is 
> resized, I have to update a menu to reflect the changes, which works just 
> fine. The app continues to work just fine until the very moment where i hit 
> one of the arrow keys or any other special key.
>
> My app is using a
>
> while ((c = wgetch(inner)) != 'q') {
>         switch (c) {
>                 case 's': ... break;
>                 case KEY_RESIZE: ... break;
>
> scheme to get the user input. Hitting special keys prior to a window resize 
> works just fine. After resizing, it does not matter whether there is a "case 
> KEY_" for the special key or not; it exits either way. (There is no default: 
> case, btw.)
>
> I believe this a bug in ncurses, although I am not absolutely sure.

hmm.  I downloaded the program (will do that _once_ - make a tar file of 
it if you want to pursue this), and tried running it.  The program dumps 
core immediately.  Here's the relevant chunk from valgrind:

==10384== 1 errors in context 1 of 1:
==10384== Invalid read of size 1
==10384==    at 0x421427D: fclose@@GLIBC_2.1 (iofclose.c:52)
==10384==    by 0x804AB93: sanity_checks (helpers.c:224)
==10384==    by 0x804B6EE: main (conf-update.c:29)
==10384==  Address 0x46 is not stack'd, malloc'd or (recently) free'd

> Unfortunately I am unable to reproduce the issue from within gdb, for some 
> reason it never triggers the case KEY_RESIZE: code, even if I tell gdb to 
> pass the SIGWINCH signal or try to send it manually.
>
> The code is available here:
>
> http://sources.gentoo.org/viewcvs.py/portage/private/blubb/conf-update/conf-update.c?view=annotate
>
> The "while ((c = wgetch(inner))..." is located around line 213.
>
> I also attach the output of `strace -o ./conf-update' in the hope of it being 
> useful.

not really (that sort of thing can be left for downloading from your 
site).

--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net