[PATCH xserver] os: avoid uninitialized offsets in backtrace

[Jeff Smith]

When xorg_backtrace calls unw_get_proc_name and an error occurs, offset
might not be set for the current frame.

Initialize offset for each frame so that the offset from another frame
cannot be used inadvertently.

Signed-off-by: Jeff Smith <whydoubt at gmail.com>
---
 os/backtrace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/os/backtrace.c b/os/backtrace.c
index 9e3e38edf..619bf145e 100644
--- a/os/backtrace.c
+++ b/os/backtrace.c
@@ -78,6 +78,7 @@ xorg_backtrace(void)
             break;
         }
 
+        off = 0;
         ret = unw_get_proc_name(&cursor, procname, 256, &off);
         if (ret && ret != -UNW_ENOMEM) {
             if (ret != -UNW_EUNSPEC)
-- 
2.14.3