[PATCH] xcb_ewmh_get_wm_icon_reply: Fix crash on error

[Uli Schlachter]

When the GetProperty request fails due to an error,
xcb_ewmh_get_wm_icon_from_reply will be called with a NULL pointer for the
reply. This function would then call xcb_get_property_value_length on this NULL
pointer which caused a crash.

Fix this by moving the NULL-pointer check before the call to value_length().

Signed-off-by: Uli Schlachter <psychon at znc.in>
---
 ewmh/ewmh.c.m4 |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/ewmh/ewmh.c.m4 b/ewmh/ewmh.c.m4
index 4a609b6..02d43f5 100644
--- a/ewmh/ewmh.c.m4
+++ b/ewmh/ewmh.c.m4
@@ -1176,13 +1176,11 @@ xcb_ewmh_get_wm_icon_from_reply(xcb_ewmh_get_wm_icon_reply_t *wm_icon,
                                 xcb_get_property_reply_t *r)
 {
   uint8_t num_icons = 0;
-  uint32_t r_value_len = xcb_get_property_value_length(r);
-  if(!r || r->type != XCB_ATOM_CARDINAL || r->format != 32 ||
-     r_value_len <= (sizeof(uint32_t) * 2))
+  if(!r || r->type != XCB_ATOM_CARDINAL || r->format != 32)
     return 0;
-
+  uint32_t r_value_len = xcb_get_property_value_length(r);
   uint32_t *r_value = (uint32_t *) xcb_get_property_value(r);
-  if(!r_value)
+  if(r_value_len <= (sizeof(uint32_t) * 2) || !r_value)
     return 0;
 
   memset(wm_icon, 0, sizeof(xcb_ewmh_get_wm_icon_reply_t));
-- 
1.7.2.3


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