* dcrt0.cc (cygwin__cxa_atexit): Fetch correct DSO handle value

	by searching dll list.  Explain why.

2 files changed, 13 insertions, 6 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 7f001ced5..fa5ca1947 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,8 @@
+2014-11-07  Corinna Vinschen  <corinna@vinschen.de>
+
+	* dcrt0.cc (cygwin__cxa_atexit): Fetch correct DSO handle value
+	by searching dll list.  Explain why.
+
 2014-11-06  Corinna Vinschen  <corinna@vinschen.de>
 
 	* dcrt0.cc (cygwin_atexit): Change preceeding comment to reflect
diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index 19fb46d2c..738860d0e 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -1239,15 +1239,17 @@ do_exit (int status)
    calls to __cxa_atexit using the *address* of __dso_handle as DSO handle.
    
    So what we do here is this:  A call to __cxa_atexit from the application
-   actually calls cygwin__cxa_atexit.  From the dso_handle value we fetch the
-   ImageBase address, which is then used as the actual DSO handle value in
-   calls to __cxa_atexit and __cxa_finalize. */
+   actually calls cygwin__cxa_atexit.  From dso_handle (which is either
+   &__dso_handle, or __dso_handle == ImageBase or NULL) we fetch the dll
+   structure of the DLL.  Then use dll::handle == ImageBase as the actual DSO
+   handle value in calls to __cxa_atexit and __cxa_finalize.
+   Thus, __cxa_atexit becomes entirely independent of the incoming value of
+   dso_handle, as long as it's *some* pointer into the DSO's address space. */
 extern "C" int
 cygwin__cxa_atexit (void (*fn)(void *), void *obj, void *dso_handle)
 {
-  if (dso_handle)
-    dso_handle = *(void **) dso_handle;
-  return __cxa_atexit (fn, obj, dso_handle);
+  dll *d = dso_handle ? dlls.find (dso_handle) : NULL;
+  return __cxa_atexit (fn, obj, d ? d->handle : NULL);
 }
 
 /* This function is only called for applications built with Cygwin versions