kernel termios troubles

[Eric Delaunay <delaunay@lix.polytechnique.fr>]

Hello,

I'm compiling packages for the next Debian release, based on GLIBC 2.1.
I packaged util-linux 2.7.1 but found a bug in the more program.
In effect, I need to hit 4 consecutive keys before the program process the
first.  They seem to be buffered, even if the tty is not set to (-icanon).

I'm trying to track down the bug but I don't find it.
I investigated the following parts of my system:

 1/ termios vs. termio:
    - I replaced any instance of termios by termio, TCGETS by TCGETA and
       TCSETSF by TCSETAF in more.c
    -> I rebuilt it and now it works.

 2/ GLIBC pre2.1 (2.0.91) termios header vs. kernel termios header:
   - I replaced the inclusion of GLIBC header (termios.h) in favor of its
     kernel counterpart (linux/termios.h).  Some minor patches were also made
     in more.c to resolve the incompatibility between both header sets.
   -> This trial didn't solved my problem.
      IMHO it's not a problem in GLIBC.

  3/ Old libc 5.3.12 termios:
   - I compiled the program on a RedHat 4.2 system with libc5
   -> same trouble, not solved.

One part I didn't investigate is the kernel sources.  I'm running 2.0.33.
IMO, I think the problem comes from it, but I've not the skills to work on.

I'd appreciate any help.
Thanks in advance.

PS: I extracted the piece of code which fails and compiled it separately.
    Here it is:

-------------cut here----------------
/* defined none or one of those symbols to switch between libc termios, libc
   termio or kernel termios. */
#undef USE_TERMIO
#undef USE_KERNEL_TERMIOS

#include <stdio.h>
#include <string.h>
#include <unistd.h>

/* based on termio */
#if defined USE_TERMIO
# include <termio.h>
# include <sys/ioctl.h>

/* based on kernel header termios */
#elif defined USE_KERNEL_TERMIOS
# include <linux/termios.h>
# define _TERMIOS_H 1		/* hack to avoid conflict with GLIBC headers */
# define winsize glibc_winsize
# define termio glibc_termio
# include <sys/ioctl.h>
# undef winsize
# undef termio

/* based on GLIBC 2 header termios */
#else
# include <termios.h>
# include <sys/ioctl.h>
#endif

#ifdef USE_TERMIO
# define set_tty(fd,argp)	ioctl(fd,TCSETAF,argp)
# define get_tty(fd,argp)	ioctl(fd,TCGETA,argp)
struct termio	otty, savetty;
#else
# define set_tty(fd,argp)	ioctl(fd,TCSETSF,argp)
# define get_tty(fd,argp)	ioctl(fd,TCGETS,argp)
struct termios	otty, savetty;
#endif

int main(int argc, char **argv) {
    char input[2] = "";

    get_tty( fileno(stdin), &otty );		/* save tty state */
    savetty = otty;
    otty.c_lflag &= ~(ICANON|ECHO);		/* unbuffered, no echo */
    set_tty( fileno(stdin), &otty );

    write( fileno(stdout), "input: ", 7 );
    read( fileno(stdin), &input, 1 );		/* wait for a key to hit */

    set_tty( fileno(stdin), &savetty );		/* restore old state */

    printf( "--> %s\n", input );
}
-------------cut here----------------

-- 
 Eric Delaunay                 | "La guerre justifie l'existence des militaires.
 delaunay@lix.polytechnique.fr | En les supprimant." Henri Jeanson (1900-1970)


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