[Bug 1428651] Re: termio ioctl returns incorrect value for suspend character

[Steven Pemberton]

termios.h says there are 17 characters (0..16) in the c_cc buffer. If I
print them all out (here I've run it three times), it seems like 4
characters change their value between calls: 8 (VSTART) 9 (VSTOP) 10
(VSUSP) 16 (VEOL2)

   0:3 1:28 2:127 3:21 4:4 5:0 6:1 7:255 8: 18   9:122 10:99   11:255 12:127 13:0 14:0 15:0 16:134 
   0:3 1:28 2:127 3:21 4:4 5:0 6:1 7:255 8:215  9:152 10:145 11:255 12:127 13:0 14:0 15:0 16:129
   0:3 1:28 2:127 3:21 4:4 5:0 6:1 7:255 8: 10   9:97    10:251 11:255 12:127 13:0 14:0 15:0 16:239 

I'll upload this program as termio2.c.

Finally the equivalent function from termios, namely tcgetattr, seems to
give the right results, consistently over calls:

   0:3 1:28 2:127 3:21 4:4 5:0 6:1 7:255 8:17 9:19 10:26 11:255 12:18
13:15 14:23 15:22 16:255

I'll upload this as termio3.c

** Attachment added: "Use ioctl to print all 17 characters."
   https://bugs.launchpad.net/ubuntu/+source/gcc-defaults/+bug/1428651/+attachment/4336010/+files/termio2.c

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Title:
  termio ioctl returns incorrect value for suspend character

Status in gcc-defaults package in Ubuntu:
  New

Bug description:
  When calling ioctl to request some special key bindings, it seems to
  return a random value for the Suspend binding (see attached C file).

  On my system, if I do a stty -a I get this:

  $ stty -a
  speed 38400 baud; rows 24; columns 80; line = 0;
  intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = M-^?; eol2 = M-^?;
  swtch = M-^?; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
  lnext = ^V; flush = ^O; min = 1; time = 0;
  -parenb -parodd cs8 hupcl -cstopb cread -clocal -crtscts
  -ignbrk brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
  -iuclc ixany imaxbel iutf8
  opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
  isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
  echoctl echoke

  If I run the enclosed C program, which does an ioctl for TCGETA:

         if (ioctl(0, TCGETA, (char*) &sgbuf) == 0) {

  and then retrieves the key bindings for interrupt, erase, and suspend
  (^C,  ^?, and ^Z in the above output). It returns Interrupt and Erase
  correctly, but it returns the wrong value for Suspend; each time I run
  the program it returns a different value, though it consistently
  returns the same (wrong) value within the program:

                                   if ((int) sgbuf.c_cc[VSUSP] != 0377) {
  			printf("Suspend=%i\n", (int)sgbuf.c_cc[VSUSP]);
  		}

  The program calls the ioctl three times to see if it always returns
  the same value within the program. It does.

  An example output:
  Erase= 127, Interrupt=3, Suspend=31
  Erase= 127, Interrupt=3, Suspend=31
  Erase= 127, Interrupt=3, Suspend=31

  but the next time I run it:

  Erase= 127, Interrupt=3, Suspend=171
  Erase= 127, Interrupt=3, Suspend=171
  Erase= 127, Interrupt=3, Suspend=171

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: gcc 4:4.8.2-1ubuntu6
  ProcVersionSignature: Ubuntu 3.13.0-46.77-generic 3.13.11-ckt15
  Uname: Linux 3.13.0-46-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.7
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Thu Mar  5 14:41:28 2015
  SourcePackage: gcc-defaults
  UpgradeStatus: No upgrade log present (probably fresh install)

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