diff options
Diffstat (limited to 'Src/Modules/curses.c')
| -rw-r--r-- | Src/Modules/curses.c | 35 |
1 files changed, 12 insertions, 23 deletions
diff --git a/Src/Modules/curses.c b/Src/Modules/curses.c index 63c6748f5..d9c19bdb1 100644 --- a/Src/Modules/curses.c +++ b/Src/Modules/curses.c @@ -1082,15 +1082,7 @@ zccmd_input(const char *nam, char **args) #endif /* - * Some documentation for wgetch() says: - - The behavior of getch and friends in the presence of handled signals - is unspecified in the SVr4 and XSI Curses documentation. Under his- - torical curses implementations, it varied depending on whether the - operating system's implementation of handled signal receipt interrupts - a read(2) call in progress or not, and also (in some implementations) - depending on whether an input timeout or non-blocking mode has been - set. + * Linux, OS X, FreeBSD documentation for wgetch() mentions: Programmers concerned about portability should be prepared for either of two cases: (a) signal receipt does not interrupt getch; (b) signal @@ -1098,21 +1090,16 @@ zccmd_input(const char *nam, char **args) EINTR. Under the ncurses implementation, handled signals never inter- rupt getch. - * The observed behavior, however, is different: wgetch() consistently - * returns ERR with EINTR when a signal is handled by the shell "trap" - * command mechanism. Further, it consistently returns ERR twice, the - * second time without even attempting to repeat the interrupted read, - * which has the side-effect of NOT updating errno. A third call will - * then begin reading again. - * - * Therefore, to properly implement signal trapping, we must (1) call - * wgetch() in a loop as long as errno remains EINTR, and (2) clear - * errno only before beginning the loop, not on every pass. + * Some observed behavior: wgetch() returns ERR with EINTR when a signal is + * handled by the shell "trap" command mechanism. Observed that it returns + * ERR twice, the second time without even attempting to repeat the + * interrupted read. Third call will then begin reading again. * - * There remains a potential bug here in that, if the caller has set - * a timeout for the read [see zccmd_timeout()] the countdown is very - * likely restarted on every call to wgetch(), so an interrupted call - * might wait much longer than desired. + * Because of widespread of previous implementation that called wget*ch + * possibly indefinitely many times after ERR/EINTR, and because of the + * above observation, wget_wch call is repeated after each ERR/EINTR, but + * errno is being reset (it wasn't) and the loop to all means should break. + * Problem: the timeout may be waited twice. */ errno = 0; @@ -1120,6 +1107,7 @@ zccmd_input(const char *nam, char **args) while ((ret = wget_wch(w->win, &wi)) == ERR) { if (errno != EINTR || errflag || retflag || breaks || exit_pending) break; + errno = 0; } switch (ret) { case OK: @@ -1146,6 +1134,7 @@ zccmd_input(const char *nam, char **args) while ((ci = wgetch(w->win)) == ERR) { if (errno != EINTR || errflag || retflag || breaks || exit_pending) return 1; + errno = 0; } if (ci >= 256) { keypadnum = ci; |