* lib/atexit.c (atexit): Check for being linked into the executable.

	If so, call __cxa_atexit with NULL DSO handle.  Explain why.
	* lib/dso_handle.c: New file providing fallback __dso_handle.

3 files changed, 30 insertions, 1 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 69ad486e0..8b1098e5c 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,5 +1,11 @@
 2014-11-05  Corinna Vinschen  <corinna@vinschen.de>
 
+	* lib/atexit.c (atexit): Check for being linked into the executable.
+	If so, call __cxa_atexit with NULL DSO handle.  Explain why.
+	* lib/dso_handle.c: New file providing fallback __dso_handle.
+
+2014-11-05  Corinna Vinschen  <corinna@vinschen.de>
+
 	* Makefile.in (NEW_FUNCTIONS): Add atexit to be not exported.
 	* lib/atexit.c (atexit): New, statically linkable version of atexit.
 	* dcrt0.cc (cygwin_atexit): Add comment to mark this function as old
diff --git a/winsup/cygwin/lib/atexit.c b/winsup/cygwin/lib/atexit.c
index 0b724771a..af82d1de7 100644
--- a/winsup/cygwin/lib/atexit.c
+++ b/winsup/cygwin/lib/atexit.c
@@ -9,6 +9,7 @@ Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
 #include <stddef.h>
+#include <windows.h>
 
 /* Statically linked replacement for the former cygwin_atexit.  We need
    the function here to be able to access the correct __dso_handle of the
@@ -18,6 +19,16 @@ atexit (void (*fn) (void))
 {
   extern int __cxa_atexit(void (*)(void*), void*, void*);
   extern void *__dso_handle;
+  extern void *__ImageBase;
 
-  return __cxa_atexit ((void (*)(void*))fn, NULL, &__dso_handle);
+  /* Check for being called from inside the executable.  If so, use NULL
+     as __dso_handle.  This allows to link executables with GCC versions
+     not providing __dso_handle in crtbegin{S}.o.  In this case our own
+     __dso_handle defined in lib/dso_handle.c is used.  However, our
+     __dso_handle always points to &__ImageBase, while the __dso_handle
+     for executables provided by crtbegin.o usually points to NULL.
+     That's what we remodel here. */
+  return __cxa_atexit ((void (*)(void*))fn, NULL,
+		       &__ImageBase == (void **) GetModuleHandleW (NULL)
+		       ? NULL : &__dso_handle);
 }
diff --git a/winsup/cygwin/lib/dso_handle.c b/winsup/cygwin/lib/dso_handle.c
new file mode 100644
index 000000000..c3069b732
--- /dev/null
+++ b/winsup/cygwin/lib/dso_handle.c
@@ -0,0 +1,12 @@
+/* dso_handle.c: Provide default __dso_handle.
+
+   Copyright 2014 Red Hat, Inc.
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+extern void *__ImageBase;
+void *__dso_handle = &__ImageBase;