* common.din (__cxa_atexit): Define as cygwin__cxa_atexit.

* dcrt0.cc (cygwin__cxa_atexit): New function.  Explain what we do.

winsup/cygwin/ChangeLog

@@ -1,3 +1,8 @@
+2014-10-29  Corinna Vinschen  <corinna@vinschen.de>
+
+	* common.din (__cxa_atexit): Define as cygwin__cxa_atexit.
+	* dcrt0.cc (cygwin__cxa_atexit): New function.  Explain what we do.
+
 2014-10-28  Corinna Vinschen  <corinna@vinschen.de>
 
 	* globals.cc (dos_file_warning): Set to false by default.

winsup/cygwin/common.din

@@ -41,7 +41,7 @@ __assert_func NOSIGFE
 __assertfail NOSIGFE
 __b64_ntop NOSIGFE
 __b64_pton NOSIGFE
-__cxa_atexit SIGFE
+__cxa_atexit = cygwin__cxa_atexit SIGFE
 __cxa_finalize SIGFE
 __dn_comp SIGFE
 __dn_expand SIGFE

winsup/cygwin/dcrt0.cc

@@ -1232,6 +1232,24 @@ do_exit (int status)
   myself.exit (n);
 }
 
+/* When introducing support for -fuse-cxa-atexit with Cygwin 1.7.32 and
+   GCC 4.8.3-3, we defined __dso_value as &ImageBase.  This supposedly allowed
+   a reproducible value which could also be easily evaluated in cygwin_atexit.
+   However, when building C++ applications with -fuse-cxa-atexit, G++ creates
+   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. */
+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);
+}
+
 extern "C" int
 cygwin_atexit (void (*fn) (void))
 {

winsup/cygwin/release/1.7.33

@@ -88,3 +88,7 @@ Bug Fixes
 
 - Fix a SEGV in some 64 bit applications explicitely dlclosing DLLs.
   Addresses: https://cygwin.com/ml/cygwin/2014-10/msg00402.html
+
+- Fix -fuse-cxa-atexit handling where dlclose fails to trigger calling
+  global dtors in dynamically loaded modules in C++ applications (and
+  thus another potential SEGV).