From b7749822ed50355d6d9f09d5b45ab3a98d7dcaae Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Mon, 27 Oct 2014 21:19:40 +0000
Subject: [PATCH] 	* dcrt0.cc (cygwin_atexit): Add workaround for broken
 atexit calls 	in __gcc_register_frame of DLLs built with gcc-4.8.3-3.

---
 winsup/cygwin/ChangeLog      |  5 +++++
 winsup/cygwin/dcrt0.cc       | 30 ++++++++++++++++++++++++++++++
 winsup/cygwin/release/1.7.33 |  3 +++
 3 files changed, 38 insertions(+)

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index bf6b00715..669f71237 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,8 @@
+2014-10-27  Corinna Vinschen  <corinna@vinschen.de>
+
+	* dcrt0.cc (cygwin_atexit): Add workaround for broken atexit calls
+	in __gcc_register_frame of DLLs built with gcc-4.8.3-3.
+
 2014-10-27  Corinna Vinschen  <corinna@vinschen.de>
 
 	* dlfcn.cc (dlopen): Drop patch accommodating SetDllDiretory from
diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index 930397f06..b2bbe8657 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -1236,7 +1236,37 @@ extern "C" int
 cygwin_atexit (void (*fn) (void))
 {
   int res;
+
   dll *d = dlls.find ((void *) _my_tls.retaddr ());
+#ifdef __x86_64__
+  /* x86_64 DLLs created with GCC 4.8.3-3 register __gcc_deregister_frame
+     as atexit function using a call to atexit, rather than __cxa_atexit.
+     Due to GCC's aggressive optimizing, cygwin_atexit doesn't get the correct
+     return address on the stack.  As a result it fails to get the HMODULE of
+     the caller and thus calls atexit rather than __cxa_atexit.  Then, if the
+     module gets dlclosed, __cxa_finalize (called from dll_list::detach) can't
+     remove __gcc_deregister_frame from the atexit function chain.  So at
+     process exit, __call_exitprocs calls __gcc_deregister_frame while the
+     module is already unloaded and the __gcc_deregister_frame function not
+     available ==> SEGV.
+
+     Workaround: If dlls.find fails, and _my_tls.retaddr is a Cygwin function
+     address, and fn is a function address in another DLL, try to find the
+     dll entry of the DLL containing fn.  Then check if fn is the address of
+     the DLLs __gcc_deregister_frame function.  If so, proceed by calling
+     __cxa_atexit, otherwise call atexit. */
+  extern void *__image_base__;
+  if (!d
+      && (uintptr_t) _my_tls.retaddr () >= (uintptr_t) &__image_base__
+      && (uintptr_t) _my_tls.retaddr () <= (uintptr_t) &_cygheap_start
+      && (uintptr_t) fn > (uintptr_t) &_cygheap_start)
+    {
+      d = dlls.find ((void *) fn);
+      if (d && (void *) GetProcAddress (d->handle, "__gcc_deregister_frame")
+	       != fn)
+	d = NULL;
+    }
+#endif
   res = d ? __cxa_atexit ((void (*) (void *)) fn, NULL, d->handle) : atexit (fn);
   return res;
 }
diff --git a/winsup/cygwin/release/1.7.33 b/winsup/cygwin/release/1.7.33
index c7acd071d..13d278648 100644
--- a/winsup/cygwin/release/1.7.33
+++ b/winsup/cygwin/release/1.7.33
@@ -83,3 +83,6 @@ Bug Fixes
 - Fix a SEGV in cygcheck if the environment variable COMSPEC is not, or
   incorrectly set.
   Addresses: https://cygwin.com/ml/cygwin/2014-10/msg00292.html
+
+- Fix a SEGV in some 64 bit applications explicitely dlclosing DLLs.
+  Addresses: https://cygwin.com/ml/cygwin/2014-10/msg00402.html