slave: emit user-notifications before dup:ing stdin/stdout/stderr

Since we need to restore the status flags anyway, there's nothing to
gain from emitting the user notifications after dup:ing the pts file
descriptor.

On the other hand, emitting user notifications *before* dup:ing means
we can still print error messages for e.g. write(3) errors.

slave.c

@@ -67,7 +67,9 @@ err:
     return false;
 }
 
-static bool
+enum user_notification_ret_t {UN_OK, UN_NO_MORE, UN_FAIL};
+
+static enum user_notification_ret_t
 emit_one_notification(int fd, const struct user_notification *notif)
 {
     const char *prefix = NULL;
@@ -93,17 +95,39 @@ emit_one_notification(int fd, const struct user_notification *notif)
         write(fd, notif->text, strlen(notif->text)) < 0 ||
         write(fd, postfix, strlen(postfix)) < 0)
     {
-        if (errno == EWOULDBLOCK || errno == EAGAIN) {
+        /*
-            /*
+         * The main process is blocking and waiting for us to close
-             * The main process is blocking and waiting for us to
+         * the error pipe. Thus, pts data will *not* be processed
-             * close the error pipe. Thus, pts data will *not* be
+         * until we've exec:d. This means we cannot write anymore once
-             * processed until we've exec:d. This means we cannot
+         * the kernel buffer is full. Don't treat this as a fatal
-             * write anymore once the kernel buffer is full. Don't
+         * error.
-             * treat this as a fatal error.
+         */
-             */
+        if (errno == EWOULDBLOCK || errno == EAGAIN)
-            return true;
+            return UN_NO_MORE;
+        else {
+            LOG_ERRNO("failed to write user-notification");
+            return UN_FAIL;
+        }
+    }
+
+    return UN_OK;
+}
+
+static bool
+emit_notifications_of_kind(int fd, const user_notifications_t *notifications,
+                           enum user_notification_kind kind)
+{
+    tll_foreach(*notifications, it) {
+        if (it->item.kind == kind) {
+            switch (emit_one_notification(fd, &it->item)) {
+            case UN_OK:
+                break;
+            case UN_NO_MORE:
+                return true;
+            case UN_FAIL:
+                return false;
+            }
         }
-        return false;
     }
 
     return true;
@@ -112,31 +136,10 @@ emit_one_notification(int fd, const struct user_notification *notif)
 static bool
 emit_notifications(int fd, const user_notifications_t *notifications)
 {
-    /* Errors first */
+    return
-    tll_foreach(*notifications, it) {
+        emit_notifications_of_kind(fd, notifications, USER_NOTIFICATION_ERROR) &&
-        if (it->item.kind == USER_NOTIFICATION_ERROR) {
+        emit_notifications_of_kind(fd, notifications, USER_NOTIFICATION_WARNING) &&
-            if (!emit_one_notification(fd, &it->item))
+        emit_notifications_of_kind(fd, notifications, USER_NOTIFICATION_DEPRECATED);
-                return false;
-        }
-    }
-
-    /* Then warnings */
-    tll_foreach(*notifications, it) {
-        if (it->item.kind == USER_NOTIFICATION_WARNING) {
-            if (!emit_one_notification(fd, &it->item))
-                return false;
-        }
-    }
-
-    /* Finally deprecation messages */
-    tll_foreach(*notifications, it) {
-        if (it->item.kind == USER_NOTIFICATION_DEPRECATED) {
-            if (!emit_one_notification(fd, &it->item))
-                return false;
-        }
-    }
-
-    return true;
 }
 
 static void
@@ -188,14 +191,6 @@ slave_exec(int ptmx, char *argv[], int err_fd, bool login_shell,
         }
     }
 
-    if (dup2(pts, STDIN_FILENO) == -1 ||
-        dup2(pts, STDOUT_FILENO) == -1 ||
-        dup2(pts, STDERR_FILENO) == -1)
-    {
-        LOG_ERRNO("failed to dup stdin/stdout/stderr");
-        goto err;
-    }
-
     if (tll_length(*notifications) > 0) {
         int flags = fcntl(pts, F_GETFL);
         if (flags < 0)
@@ -209,6 +204,14 @@ slave_exec(int ptmx, char *argv[], int err_fd, bool login_shell,
         fcntl(pts, F_SETFL, flags);
     }
 
+    if (dup2(pts, STDIN_FILENO) == -1 ||
+        dup2(pts, STDOUT_FILENO) == -1 ||
+        dup2(pts, STDERR_FILENO) == -1)
+    {
+        LOG_ERRNO("failed to dup stdin/stdout/stderr");
+        goto err;
+    }
+
     close(pts);
     pts = -1;
 

user-notification.h

@@ -2,12 +2,14 @@
 
 #include <tllist.h>
 
+enum user_notification_kind {
+    USER_NOTIFICATION_DEPRECATED,
+    USER_NOTIFICATION_WARNING,
+    USER_NOTIFICATION_ERROR,
+};
+
 struct user_notification {
-    enum {
+    enum user_notification_kind kind;
-        USER_NOTIFICATION_DEPRECATED,
-        USER_NOTIFICATION_WARNING,
-        USER_NOTIFICATION_ERROR,
-    } kind;
     char *text;
 };