ash: don't mistake errors for timeouts in read built-in

Commit e07a73a15 (ash: bring 'read' built-in closer to bash)
added code to treat a timeout differently from an error returned
by poll(2).  This falsely assumed that only an EINTR error was
relevant.  We must allow for other errors.

Adds 16 bytes.

(GitHub issue #502)

1 files changed, 9 insertions, 6 deletions

diff --git a/shell/shell_common.c b/shell/shell_common.c
index 2a876acac..6ea08ad74 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -227,20 +227,23 @@ shell_builtin_read(struct builtin_read_params *params)
                 pfd[0].events = POLLIN;
 //TODO race with a signal arriving just before the poll!
 #if ENABLE_PLATFORM_MINGW32
-                /* Don't poll if timeout is -1, it hurts performance. */
+                /* Don't poll if timeout is -1, it hurts performance.  The
+                 * caution above about interrupts isn't relevant on Windows
+                 * where Ctrl-C causes an event, not a signal.
+                 */
                 if (timeout >= 0)
 #endif
                 if (poll(pfd, 1, timeout) <= 0) {
                         /* timed out, or EINTR */
                         err = errno;
 #if ENABLE_PLATFORM_MINGW32
-                        /* Windows poll(2) doesn't do EINTR, we timed out */
-                        retval = (const char *)(uintptr_t)2;
-                        break;
-#else
+                        if (!err) {
+                                retval = (const char *)(uintptr_t)2;
+                                break;
+                        }
+#endif
                         retval = (const char *)(uintptr_t)1;
                         goto ret;
-#endif
                 }
 #if ENABLE_PLATFORM_MINGW32
                 if (isatty(fd)) {