top: improve control character handling in line editingHEADmaster

terminfo is notoriously unreliable when it comes to the
erase character. Use the terminal setting instead. Also
hardcode both commonly used characters just to be safe.
Do not assign unwanted actions to '\0'.

Reference(s):
https://gitlab.com/procps-ng/procps/-/issues/278

1 files changed, 25 insertions, 18 deletions

diff --git a/src/top/top.c b/src/top/top.c
index 98444fd..07fcb68 100644
--- a/src/top/top.c
+++ b/src/top/top.c
@@ -1167,6 +1167,7 @@ static int iokey (int action) {
       { NULL, kbd_PGDN  }, { NULL, kbd_PGUP  }, { NULL, kbd_END   }, { NULL, kbd_BTAB  },
          // remainder are alternatives for above, just in case...
          // ( the h,j,k,l entries are the vim cursor motion keys )
+      { "\b",       kbd_BKSP  }, { "\177",     kbd_BKSP  }, /* backspace      */
       { "\033h",    kbd_LEFT  }, { "\033j",    kbd_DOWN  }, /* meta+      h,j */
       { "\033k",    kbd_UP    }, { "\033l",    kbd_RIGHT }, /* meta+      k,l */
       { "\033\010", kbd_HOME  }, { "\033\012", kbd_PGDN  }, /* ctrl+meta+ h,j */
@@ -1177,6 +1178,7 @@ static int iokey (int action) {
       { "\xC2\x8B", kbd_PGUP  }, { "\xC2\x8C", kbd_END   }, /* ctrl+meta+ k,l (some xterms) */
       { "\033\011", kbd_BTAB  }
    };
+   static char erase[2];
 #ifdef TERMIOS_ONLY
    char buf[SMLBUFSIZ], *pb;
 #else
@@ -1187,24 +1189,31 @@ static int iokey (int action) {
    int i;
 
    if (action == IOKEY_INIT) {
-    #define tOk(s)  s ? s : ""
-      tinfo_tab[0].str  = tOk(key_backspace);
-      tinfo_tab[1].str  = tOk(key_ic);
-      tinfo_tab[2].str  = tOk(key_dc);
-      tinfo_tab[3].str  = tOk(key_left);
-      tinfo_tab[4].str  = tOk(key_down);
-      tinfo_tab[5].str  = tOk(key_up);
-      tinfo_tab[6].str  = tOk(key_right);
-      tinfo_tab[7].str  = tOk(key_home);
-      tinfo_tab[8].str  = tOk(key_npage);
-      tinfo_tab[9].str  = tOk(key_ppage);
-      tinfo_tab[10].str = tOk(key_end);
-      tinfo_tab[11].str = tOk(back_tab);
+#ifndef _POSIX_VDISABLE
+#define _POSIX_VDISABLE fpathconf(STDIN_FILENO, _PC_VDISABLE)
+#endif
+      if (Tty_original.c_cc[VERASE] == _POSIX_VDISABLE)
+         tinfo_tab[0].str = key_backspace;
+      else {
+         *erase           = Tty_original.c_cc[VERASE];
+         tinfo_tab[0].str = erase;
+      }
+      tinfo_tab[1].str  = key_ic;
+      tinfo_tab[2].str  = key_dc;
+      tinfo_tab[3].str  = key_left;
+      tinfo_tab[4].str  = key_down;
+      tinfo_tab[5].str  = key_up;
+      tinfo_tab[6].str  = key_right;
+      tinfo_tab[7].str  = key_home;
+      tinfo_tab[8].str  = key_npage;
+      tinfo_tab[9].str  = key_ppage;
+      tinfo_tab[10].str = key_end;
+      tinfo_tab[11].str = back_tab;
       // next is critical so returned results match bound terminfo keys
-      putp(tOk(keypad_xmit));
+      if (keypad_xmit)
+         putp(keypad_xmit);
       // ( converse keypad_local issued at pause/pgm end, just in case )
       return 0;
-    #undef tOk
    }
 
    if (action == IOKEY_ONCE) {
@@ -1234,7 +1243,7 @@ static int iokey (int action) {
    else if (pb > buf && '\033' == *(pb - 1)) --pb;
 
    for (i = 0; i < MAXTBL(tinfo_tab); i++)
-      if (!strcmp(tinfo_tab[i].str, pb))
+      if (tinfo_tab[i].str && !strcmp(tinfo_tab[i].str, pb))
          return tinfo_tab[i].key;
 
    // no match, so we'll return single non-escaped keystrokes only
@@ -4473,8 +4482,6 @@ static void whack_terminal (void) {
    tmptty.c_oflag &= ~TAB3;
    tmptty.c_iflag |= BRKINT;
    tmptty.c_iflag &= ~IGNBRK;
-   if (key_backspace && 1 == strlen(key_backspace))
-      tmptty.c_cc[VERASE] = *key_backspace;
 #ifdef TERMIOS_ONLY
    if (-1 == tcsetattr(STDIN_FILENO, TCSAFLUSH, &tmptty))
       error_exit(fmtmk(N_fmt(FAIL_tty_set_fmt), strerror(errno)));