Add objc_setUncaughtExceptionHandler() API

CMakeLists.txt

@@ -84,6 +84,7 @@ set(libobjc_HDRS
 	objc/objc-arc.h
 	objc/objc-auto.h
 	objc/objc-class.h
+	objc/objc-exception.h
 	objc/objc-runtime.h
 	objc/objc-visibility.h
 	objc/objc.h

Test/UnexpectedException.m

@@ -34,7 +34,7 @@ int main(void)
 	SetUnhandledExceptionFilter(&_UnhandledExceptionFilter);
 #endif
 
-	_objc_unexpected_exception = _UncaughtExceptionHandler;
+	objc_setUncaughtExceptionHandler(_UncaughtExceptionHandler);
 	@throw exceptionObj;
 	assert(0 && "should not be reached!");
 

eh_personality.c

@@ -4,6 +4,7 @@
 #include "dwarf_eh.h"
 #include "objc/runtime.h"
 #include "objc/hooks.h"
+#include "objc/objc-exception.h"
 #include "class.h"
 #include "objcxx_eh.h"
 
@@ -760,3 +761,8 @@ void objc_exception_rethrow(struct _Unwind_Exception *e)
 	_Unwind_Resume_or_Rethrow(e);
 	abort();
 }
+
+objc_uncaught_exception_handler objc_setUncaughtExceptionHandler(objc_uncaught_exception_handler handler)
+{
+	return __atomic_exchange_n(&_objc_unexpected_exception, handler, __ATOMIC_SEQ_CST);
+}

eh_win32_msvc.cc

@@ -4,7 +4,7 @@
 #include <vector>
 
 #include "objc/runtime.h"
-#include "objc/hooks.h"
+#include "objc/objc-exception.h"
 #include "visibility.h"
 
 #include <windows.h>
@@ -57,6 +57,7 @@ struct _MSVC_ThrowInfo
 };
 
 static LPTOP_LEVEL_EXCEPTION_FILTER originalUnhandledExceptionFilter = nullptr;
+void (*_objc_unexpected_exception)(id exception);
 LONG WINAPI _objc_unhandled_exception_filter(struct _EXCEPTION_POINTERS* exceptionInfo);
 
 #if defined(_WIN64)
@@ -197,17 +198,6 @@ OBJC_PUBLIC extern "C" void objc_exception_throw(id object)
 	exception.ExceptionInformation[2] = reinterpret_cast<ULONG_PTR>(&ti);
 	exception.ExceptionInformation[3] = reinterpret_cast<ULONG_PTR>(&x);
 
-	// Set unhandled exception filter to support _objc_unexpected_exception hook.
-	// Unfortunately there doesn't seem to be a better place to call this, as
-	// installing it at construction time means that it will get overwritten by
-	// the handler installed by the VC runtime. This way it works, but as a side
-	// effect throwing exceptions will overwrite any previously installed handler,
-	// so we save it and call it as part of our handler.
-	LPTOP_LEVEL_EXCEPTION_FILTER previousExceptionFilter = SetUnhandledExceptionFilter(&_objc_unhandled_exception_filter);
-	if (previousExceptionFilter != &_objc_unhandled_exception_filter) {
-		originalUnhandledExceptionFilter = previousExceptionFilter;
-	}
-
 #ifdef _WIN64
  	RtlRaiseException(&exception);
 #else
@@ -282,3 +272,16 @@ LONG WINAPI _objc_unhandled_exception_filter(struct _EXCEPTION_POINTERS* excepti
 	// Since this is the last one, it is not likely to find any more.
 	return EXCEPTION_CONTINUE_SEARCH;
 }
+
+OBJC_PUBLIC extern "C" objc_uncaught_exception_handler objc_setUncaughtExceptionHandler(objc_uncaught_exception_handler handler)
+{
+	objc_uncaught_exception_handler previousHandler = __atomic_exchange_n(&_objc_unexpected_exception, handler, __ATOMIC_SEQ_CST);
+
+	// set unhandled exception filter to support hook
+	LPTOP_LEVEL_EXCEPTION_FILTER previousExceptionFilter = SetUnhandledExceptionFilter(&_objc_unhandled_exception_filter);
+	if (previousExceptionFilter != &_objc_unhandled_exception_filter) {
+		originalUnhandledExceptionFilter = previousExceptionFilter;
+	}
+
+	return previousHandler;
+}

objc/hooks.h

@@ -46,12 +46,17 @@ OBJC_PUBLIC extern struct objc_slot *(*__objc_msg_forward3)(id, SEL) OBJC_DEPREC
  * handles the forwarding.
  */
 OBJC_PUBLIC extern IMP (*__objc_msg_forward2)(id, SEL);
+
+#ifndef _WIN32
 /**
  * Hook defined for handling unhandled exceptions.  If the unwind library
  * reaches the end of the stack without finding a handler then this hook is
  * called.
+ * Deprecated. Use objc_setUncaughtExceptionHandler() instead.
  */
 OBJC_HOOK void (*_objc_unexpected_exception)(id exception);
+#endif
+
 /**
  * Hook defined to return the class to be used for boxing a foreign exception
  * type.  The class must implement:

objc/objc-exception.h

@@ -0,0 +1,33 @@
+#if defined(__clang__) && !defined(__OBJC_RUNTIME_INTERNAL__)
+#pragma clang system_header
+#endif
+#include "objc-visibility.h"
+
+#ifndef __OBJC_EXCEPTION_INCLUDED__
+#define __OBJC_EXCEPTION_INCLUDED__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef void (*objc_uncaught_exception_handler)(id exception);
+
+/** 
+ * Throw a runtime exception. Inserted by the compiler in place of @throw.
+ */
+OBJC_PUBLIC
+void objc_exception_throw(id object);
+
+/**
+ * Installs handler for uncaught Objective-C exceptions.  If the unwind library
+ * reaches the end of the stack without finding a handler then the handler is
+ * called. Returns the previous handler.
+ */
+OBJC_PUBLIC
+objc_uncaught_exception_handler objc_setUncaughtExceptionHandler(objc_uncaught_exception_handler handler);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __OBJC_EXCEPTION_INCLUDED__