[Xcb] [PATCH:libxcb v5] Return connection failure if display string specifies non-existent string

[Alan Coopersmith]

Matches the behaviour of Xlib - if you set DISPLAY to :0.1 but only have
one screen, closes connection and returns error.

This introduces a new connection error code:
XCB_CONN_CLOSED_INVALID_SCREEN

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu at apple.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
---
 src/xcb.h      |    4 ++++
 src/xcb_conn.c |    5 +++++
 src/xcb_util.c |   10 ++++++++++
 3 files changed, 19 insertions(+)

v2: Jeremy introduced new connection error code XCB_CONN_CLOSED_INVALID_SCREEN
    https://bugs.freedesktop.org/attachment.cgi?id=66113&action=edit

v3: Jeremy fixed my bug in failing to dereference pscreen before comparing
    https://bugs.freedesktop.org/attachment.cgi?id=66114&action=edit

v4: Made error path more like the rest of the function, to avoid memory leaks
    https://bugs.freedesktop.org/attachment.cgi?id=66115&action=edit

v5: Add a new static const object for XCB_CONN_CLOSED_INVALID_SCREEN for
    _xcb_conn_ret_error to return so callers can see the new error code.
    Don't check screen number if a previous step had an error, since that
    means c just points to an int now, not a full xcb_connection_t.


diff --git a/src/xcb.h b/src/xcb.h
index 179af84..f7dc6af 100644
--- a/src/xcb.h
+++ b/src/xcb.h
@@ -84,6 +84,9 @@ extern "C" {
 /** Connection closed, error during parsing display string. */
 #define XCB_CONN_CLOSED_PARSE_ERR 5
 
+/** Connection closed because the server does not have a screen matching the display. */
+#define XCB_CONN_CLOSED_INVALID_SCREEN 6
+
 #define XCB_TYPE_PAD(T,I) (-(I) & (sizeof(T) > 4 ? 3 : sizeof(T) - 1))
 
 /* Opaque structures */
@@ -423,6 +426,7 @@ int xcb_get_file_descriptor(xcb_connection_t *c);
  * @return XCB_CONN_CLOSED_MEM_INSUFFICIENT, when memory not available.
  * @return XCB_CONN_CLOSED_REQ_LEN_EXCEED, exceeding request length that server accepts.
  * @return XCB_CONN_CLOSED_PARSE_ERR, error during parsing display string.
+ * @return XCB_CONN_CLOSED_INVALID_SCREEN, because the server does not have a screen matching the display.
  */
 int xcb_connection_has_error(xcb_connection_t *c);
 
diff --git a/src/xcb_conn.c b/src/xcb_conn.c
index 7202cc5..7979491 100644
--- a/src/xcb_conn.c
+++ b/src/xcb_conn.c
@@ -66,6 +66,7 @@ typedef struct {
 static const int xcb_con_error = XCB_CONN_ERROR;
 static const int xcb_con_closed_mem_er = XCB_CONN_CLOSED_MEM_INSUFFICIENT;
 static const int xcb_con_closed_parse_er = XCB_CONN_CLOSED_PARSE_ERR;
+static const int xcb_con_closed_screen_er = XCB_CONN_CLOSED_INVALID_SCREEN;
 
 static int set_fd_flags(const int fd)
 {
@@ -349,6 +350,10 @@ xcb_connection_t *_xcb_conn_ret_error(int err)
         {
             return (xcb_connection_t *) &xcb_con_closed_parse_er;
         }
+        case XCB_CONN_CLOSED_INVALID_SCREEN:
+        {
+            return (xcb_connection_t *) &xcb_con_closed_screen_er;
+        }
         case XCB_CONN_ERROR:
         default:
         {
diff --git a/src/xcb_util.c b/src/xcb_util.c
index e480d75..463d085 100644
--- a/src/xcb_util.c
+++ b/src/xcb_util.c
@@ -467,6 +467,16 @@ xcb_connection_t *xcb_connect_to_display_with_auth_info(const char *displayname,
     else
         c = xcb_connect_to_fd(fd, 0);
 
+    if(c->has_error)
+        goto out;
+
+    /* Make sure requested screen number is in bounds for this server */
+    if((screenp != NULL) && (*screenp >= (int) c->setup->roots_len)) {
+        xcb_disconnect(c);
+        c = _xcb_conn_ret_error(XCB_CONN_CLOSED_INVALID_SCREEN);
+        goto out;
+    }
+
 out:
     free(host);
     free(protocol);
-- 
1.7.9.2