Changes in libcfa/src/exception.c [3b9c674:851fd92]

File:

• libcfa/src/exception.c (modified) (24 diffs)

libcfa/src/exception.c

@@ -9 +9 @@
 // Author           : Andrew Beach
 // Created On       : Mon Jun 26 15:13:00 2017
-// Last Modified By : Peter A. Buhr
-// Last Modified On : Thu Feb 22 18:17:34 2018
-// Update Count     : 11
+// Last Modified By : Andrew Beach
+// Last Modified On : Tue Apr 14 12:01:00 2020
+// Update Count     : 18
 //
 
+// Normally we would get this from the CFA prelude.
 #include <stddef.h> // for size_t
 
 #include "exception.h"
 
-// Implementation of the secret header.
+// Implementation of the secret header is hardware dependent.
+#if !( defined( __x86_64 ) || defined( __i386 ) )
+#error Exception Handling: No known architecture detected.
+#endif
 
 #include <stdlib.h>
@@ -24 +28 @@
 #include <unwind.h>
 #include <bits/debug.hfa>
+#include "stdhdr/assert.h"
 
 // FIX ME: temporary hack to keep ARM build working
 #ifndef _URC_FATAL_PHASE1_ERROR
-#define _URC_FATAL_PHASE1_ERROR 2
+#define _URC_FATAL_PHASE1_ERROR 3
 #endif // ! _URC_FATAL_PHASE1_ERROR
 #ifndef _URC_FATAL_PHASE2_ERROR
@@ -35 +40 @@
 #include "lsda.h"
 
+/* The exception class for our exceptions. Because of the vendor component
+ * its value would not be standard.
+ * Vendor: UWPL
+ * Language: CFA\0
+ */
+const _Unwind_Exception_Class __cfaehm_exception_class = 0x4c50575500414643;
 
 // Base exception vtable is abstract, you should not have base exceptions.
-struct __cfaabi_ehm__base_exception_t_vtable
-                ___cfaabi_ehm__base_exception_t_vtable_instance = {
+struct __cfaehm_base_exception_t_vtable
+                ___cfaehm_base_exception_t_vtable_instance = {
         .parent = NULL,
         .size = 0,
@@ -49 +60 @@
 // Temperary global exception context. Does not work with concurency.
 struct exception_context_t {
-    struct __cfaabi_ehm__try_resume_node * top_resume;
-    struct __cfaabi_ehm__try_resume_node * current_resume;
-
-    exception_t * current_exception;
-    int current_handler_index;
-} shared_stack = {NULL, NULL, 0, 0};
+        struct __cfaehm_try_resume_node * top_resume;
+
+        exception_t * current_exception;
+        int current_handler_index;
+} static shared_stack = {NULL, NULL, 0};
 
 // Get the current exception context.
@@ -62 +72 @@
         return &shared_stack;
 }
-//#define SAVE_EXCEPTION_CONTEXT(to_name)
-//struct exception_context_t * to_name = this_exception_context();
-//exception * this_exception() {
-//    return this_exception_context()->current_exception;
-//}
-
-
-// This macro should be the only thing that needs to change across machines.
-// Used in the personality function, way down in termination.
-// struct _Unwind_Context * -> _Unwind_Reason_Code(*)(exception_t *)
-#define MATCHER_FROM_CONTEXT(ptr_to_context) \
-        (*(_Unwind_Reason_Code(**)(exception_t *))(_Unwind_GetCFA(ptr_to_context) + 8))
 
 
 // RESUMPTION ================================================================
 
-void __cfaabi_ehm__throw_resume(exception_t * except) {
-
-        __cfaabi_dbg_print_safe("Throwing resumption exception\n");
-
-        struct __cfaabi_ehm__try_resume_node * original_head = shared_stack.current_resume;
-        struct __cfaabi_ehm__try_resume_node * current =
-                (original_head) ? original_head->next : shared_stack.top_resume;
+static void reset_top_resume(struct __cfaehm_try_resume_node ** store) {
+        this_exception_context()->top_resume = *store;
+}
+
+void __cfaehm_throw_resume(exception_t * except) {
+        struct exception_context_t * context = this_exception_context();
+
+        __cfadbg_print_safe(exception, "Throwing resumption exception\n");
+
+        __attribute__((cleanup(reset_top_resume)))
+        struct __cfaehm_try_resume_node * original_head = context->top_resume;
+        struct __cfaehm_try_resume_node * current = context->top_resume;
 
         for ( ; current ; current = current->next) {
-                shared_stack.current_resume = current;
+                context->top_resume = current->next;
                 if (current->handler(except)) {
-                        shared_stack.current_resume = original_head;
                         return;
                 }
         }
 
-        __cfaabi_dbg_print_safe("Unhandled exception\n");
-        shared_stack.current_resume = original_head;
+        __cfadbg_print_safe(exception, "Unhandled exception\n");
 
         // Fall back to termination:
-        __cfaabi_ehm__throw_terminate(except);
+        __cfaehm_throw_terminate(except);
         // TODO: Default handler for resumption.
 }
@@ -106 +107 @@
 // be added after the node is built but before it is made the top node.
 
-void __cfaabi_ehm__try_resume_setup(struct __cfaabi_ehm__try_resume_node * node,
+void __cfaehm_try_resume_setup(struct __cfaehm_try_resume_node * node,
                         _Bool (*handler)(exception_t * except)) {
-        node->next = shared_stack.top_resume;
+        struct exception_context_t * context = this_exception_context();
+        node->next = context->top_resume;
         node->handler = handler;
-        shared_stack.top_resume = node;
-}
-
-void __cfaabi_ehm__try_resume_cleanup(struct __cfaabi_ehm__try_resume_node * node) {
-        shared_stack.top_resume = node->next;
+        context->top_resume = node;
+}
+
+void __cfaehm_try_resume_cleanup(struct __cfaehm_try_resume_node * node) {
+        struct exception_context_t * context = this_exception_context();
+        context->top_resume = node->next;
 }
 
@@ -123 +126 @@
 // May have to move to cfa for constructors and destructors (references).
 
-struct __cfaabi_ehm__node {
-        struct __cfaabi_ehm__node * next;
+// How to clean up an exception in various situations.
+static void __cfaehm_exception_cleanup(
+                _Unwind_Reason_Code reason,
+                struct _Unwind_Exception * exception) {
+        switch (reason) {
+        case _URC_FOREIGN_EXCEPTION_CAUGHT:
+                // This one we could clean-up to allow cross-language exceptions.
+        case _URC_FATAL_PHASE1_ERROR:
+        case _URC_FATAL_PHASE2_ERROR:
+        default:
+                abort();
+        }
+}
+
+// We need a piece of storage to raise the exception, for now its a single
+// piece.
+static struct _Unwind_Exception this_exception_storage;
+
+struct __cfaehm_node {
+        struct __cfaehm_node * next;
 };
 
 #define NODE_TO_EXCEPT(node) ((exception_t *)(1 + (node)))
-#define EXCEPT_TO_NODE(except) ((struct __cfaabi_ehm__node *)(except) - 1)
+#define EXCEPT_TO_NODE(except) ((struct __cfaehm_node *)(except) - 1)
 
 // Creates a copy of the indicated exception and sets current_exception to it.
-static void __cfaabi_ehm__allocate_exception( exception_t * except ) {
+static void __cfaehm_allocate_exception( exception_t * except ) {
         struct exception_context_t * context = this_exception_context();
 
         // Allocate memory for the exception.
-        struct __cfaabi_ehm__node * store = malloc(
-                sizeof( struct __cfaabi_ehm__node ) + except->virtual_table->size );
+        struct __cfaehm_node * store = malloc(
+                sizeof( struct __cfaehm_node ) + except->virtual_table->size );
 
         if ( ! store ) {
@@ -149 +170 @@
         // Copy the exception to storage.
         except->virtual_table->copy( context->current_exception, except );
+
+        // Set up the exception storage.
+        this_exception_storage.exception_class = __cfaehm_exception_class;
+        this_exception_storage.exception_cleanup = __cfaehm_exception_cleanup;
 }
 
 // Delete the provided exception, unsetting current_exception if relivant.
-static void __cfaabi_ehm__delete_exception( exception_t * except ) {
+static void __cfaehm_delete_exception( exception_t * except ) {
         struct exception_context_t * context = this_exception_context();
 
-        __cfaabi_dbg_print_safe("Deleting Exception\n");
+        __cfadbg_print_safe(exception, "Deleting Exception\n");
 
         // Remove the exception from the list.
-        struct __cfaabi_ehm__node * to_free = EXCEPT_TO_NODE(except);
-        struct __cfaabi_ehm__node * node;
+        struct __cfaehm_node * to_free = EXCEPT_TO_NODE(except);
+        struct __cfaehm_node * node;
 
         if ( context->current_exception == except ) {
@@ -167 +192 @@
                 node = EXCEPT_TO_NODE(context->current_exception);
                 // It may always be in the first or second position.
-                while( to_free != node->next ) {
+                while ( to_free != node->next ) {
                         node = node->next;
                 }
@@ -179 +204 @@
 
 // If this isn't a rethrow (*except==0), delete the provided exception.
-void __cfaabi_ehm__cleanup_terminate( void * except ) {
-        if ( *(void**)except ) __cfaabi_ehm__delete_exception( *(exception_t **)except );
-}
-
-
-// We need a piece of storage to raise the exception
-struct _Unwind_Exception this_exception_storage;
+void __cfaehm_cleanup_terminate( void * except ) {
+        if ( *(void**)except ) __cfaehm_delete_exception( *(exception_t **)except );
+}
 
 // Function needed by force unwind
@@ -192 +213 @@
                 int version,
                 _Unwind_Action actions,
-                _Unwind_Exception_Class exceptionClass,
+                _Unwind_Exception_Class exception_class,
                 struct _Unwind_Exception * unwind_exception,
-                struct _Unwind_Context * context,
-                void * some_param) {
-        if( actions & _UA_END_OF_STACK  ) exit(1);
-        if( actions & _UA_CLEANUP_PHASE ) return _URC_NO_REASON;
-
-        return _URC_FATAL_PHASE2_ERROR;
+                struct _Unwind_Context * unwind_context,
+                void * stop_param) {
+        // Verify actions follow the rules we expect.
+        verify((actions & _UA_CLEANUP_PHASE) && (actions & _UA_FORCE_UNWIND));
+        verify(!(actions & (_UA_SEARCH_PHASE | _UA_HANDER_FRAME)));
+
+        if ( actions & _UA_END_OF_STACK ) {
+                exit(1);
+        } else {
+                return _URC_NO_REASON;
+        }
 }
 
 // The exception that is being thrown must already be stored.
-__attribute__((noreturn)) void __cfaabi_ehm__begin_unwind(void) {
+static __attribute__((noreturn)) void __cfaehm_begin_unwind(void) {
         if ( ! this_exception_context()->current_exception ) {
                 printf("UNWIND ERROR missing exception in begin unwind\n");
                 abort();
         }
-
 
         // Call stdlibc to raise the exception
@@ -220 +245 @@
         // the whole stack.
 
-        if( ret == _URC_END_OF_STACK ) {
+        if ( ret == _URC_END_OF_STACK ) {
                 // No proper handler was found. This can be handled in many ways, C++ calls std::terminate.
                 // Here we force unwind the stack, basically raising a cancellation.
@@ -235 +260 @@
 }
 
-void __cfaabi_ehm__throw_terminate( exception_t * val ) {
-        __cfaabi_dbg_print_safe("Throwing termination exception\n");
-
-        __cfaabi_ehm__allocate_exception( val );
-        __cfaabi_ehm__begin_unwind();
-}
-
-void __cfaabi_ehm__rethrow_terminate(void) {
-        __cfaabi_dbg_print_safe("Rethrowing termination exception\n");
-
-        __cfaabi_ehm__begin_unwind();
-}
-
-#pragma GCC push_options
-#pragma GCC optimize("O0")
+void __cfaehm_throw_terminate( exception_t * val ) {
+        __cfadbg_print_safe(exception, "Throwing termination exception\n");
+
+        __cfaehm_allocate_exception( val );
+        __cfaehm_begin_unwind();
+}
+
+void __cfaehm_rethrow_terminate(void) {
+        __cfadbg_print_safe(exception, "Rethrowing termination exception\n");
+
+        __cfaehm_begin_unwind();
+}
 
 // This is our personality routine. For every stack frame annotated with
 // ".cfi_personality 0x3,__gcfa_personality_v0" this function will be called twice when unwinding.
 //  Once in the search phase and once in the cleanup phase.
-_Unwind_Reason_Code __gcfa_personality_v0 (
-                int version, _Unwind_Action actions, unsigned long long exceptionClass,
-                struct _Unwind_Exception* unwind_exception,
-                struct _Unwind_Context* context)
+_Unwind_Reason_Code __gcfa_personality_v0(
+                int version,
+                _Unwind_Action actions,
+                unsigned long long exception_class,
+                struct _Unwind_Exception * unwind_exception,
+                struct _Unwind_Context * unwind_context)
 {
 
-        //__cfaabi_dbg_print_safe("CFA: 0x%lx\n", _Unwind_GetCFA(context));
-        __cfaabi_dbg_print_safe("Personality function (%d, %x, %llu, %p, %p):",
-                        version, actions, exceptionClass, unwind_exception, context);
-
-        // If we've reached the end of the stack then there is nothing much we can do...
-        if( actions & _UA_END_OF_STACK ) return _URC_END_OF_STACK;
-
+        //__cfadbg_print_safe(exception, "CFA: 0x%lx\n", _Unwind_GetCFA(context));
+        __cfadbg_print_safe(exception, "Personality function (%d, %x, %llu, %p, %p):",
+                        version, actions, exception_class, unwind_exception, unwind_context);
+
+        // Verify that actions follow the rules we expect.
+        // This function should never be called at the end of the stack.
+        verify(!(actions & _UA_END_OF_STACK));
+        // Either only the search phase flag is set or...
         if (actions & _UA_SEARCH_PHASE) {
-                __cfaabi_dbg_print_safe(" lookup phase");
-        }
-        else if (actions & _UA_CLEANUP_PHASE) {
-                __cfaabi_dbg_print_safe(" cleanup phase");
-        }
-        // Just in case, probably can't actually happen
-        else {
-                printf(" error\n");
-                return _URC_FATAL_PHASE1_ERROR;
+                verify(actions == _UA_SEARCH_PHASE);
+                __cfadbg_print_safe(exception, " lookup phase");
+        // ... we are in clean-up phase.
+        } else {
+                verify(actions & _UA_CLEANUP_PHASE);
+                __cfadbg_print_safe(exception, " cleanup phase");
+                // We shouldn't be the handler frame during forced unwind.
+                if (actions & _UA_HANDLER_FRAME) {
+                        verify(!(actions & _UA_FORCE_UNWIND));
+                        __cfadbg_print_safe(exception, " (handler frame)");
+                } else if (actions & _UA_FORCE_UNWIND) {
+                        __cfadbg_print_safe(exception, " (force unwind)");
+                }
         }
 
         // Get a pointer to the language specific data from which we will read what we need
-        const unsigned char * lsd = (const unsigned char*) _Unwind_GetLanguageSpecificData( context );
-
-        if( !lsd ) {    //Nothing to do, keep unwinding
+        const unsigned char * lsd = _Unwind_GetLanguageSpecificData( unwind_context );
+
+        if ( !lsd ) {   //Nothing to do, keep unwinding
                 printf(" no LSD");
                 goto UNWIND;
@@ -289 +318 @@
         // Get the instuction pointer and a reading pointer into the exception table
         lsda_header_info lsd_info;
-        const unsigned char * cur_ptr = parse_lsda_header(context, lsd, &lsd_info);
-        _Unwind_Ptr instruction_ptr = _Unwind_GetIP( context );
+        const unsigned char * cur_ptr = parse_lsda_header(unwind_context, lsd, &lsd_info);
+        _Unwind_Ptr instruction_ptr = _Unwind_GetIP(unwind_context);
+
+        struct exception_context_t * context = this_exception_context();
 
         // Linearly search the table for stuff to do
-        while( cur_ptr < lsd_info.action_table ) {
+        while ( cur_ptr < lsd_info.action_table ) {
                 _Unwind_Ptr callsite_start;
                 _Unwind_Ptr callsite_len;
@@ -306 +337 @@
 
                 // Have we reach the correct frame info yet?
-                if( lsd_info.Start + callsite_start + callsite_len < instruction_ptr ) {
+                if ( lsd_info.Start + callsite_start + callsite_len < instruction_ptr ) {
 #ifdef __CFA_DEBUG_PRINT__
                         void * ls = (void*)lsd_info.Start;
@@ -314 +345 @@
                         void * ep = (void*)lsd_info.Start + callsite_start + callsite_len;
                         void * ip = (void*)instruction_ptr;
-                        __cfaabi_dbg_print_safe("\nfound %p - %p (%p, %p, %p), looking for %p\n",
+                        __cfadbg_print_safe(exception, "\nfound %p - %p (%p, %p, %p), looking for %p\n",
                                         bp, ep, ls, cs, cl, ip);
 #endif // __CFA_DEBUG_PRINT__
@@ -321 +352 @@
 
                 // Have we gone too far?
-                if( lsd_info.Start + callsite_start > instruction_ptr ) {
+                if ( lsd_info.Start + callsite_start > instruction_ptr ) {
                         printf(" gone too far");
                         break;
                 }
 
-                // Something to do?
-                if( callsite_landing_pad ) {
-                        // Which phase are we in
-                        if (actions & _UA_SEARCH_PHASE) {
-                                // In search phase, these means we found a potential handler we must check.
-
-                                // We have arbitrarily decided that 0 means nothing to do and 1 means there is
-                                // a potential handler. This doesn't seem to conflict the gcc default behavior.
-                                if (callsite_action != 0) {
-                                        // Now we want to run some code to see if the handler matches
-                                        // This is the tricky part where we want to the power to run arbitrary code
-                                        // However, generating a new exception table entry and try routine every time
-                                        // is way more expansive than we might like
-                                        // The information we have is :
-                                        //  - The GR (Series of registers)
-                                        //    GR1=GP Global Pointer of frame ref by context
-                                        //  - The instruction pointer
-                                        //  - The instruction pointer info (???)
-                                        //  - The CFA (Canonical Frame Address)
-                                        //  - The BSP (Probably the base stack pointer)
-
-
-                                        // The current apprach uses one exception table entry per try block
-                                        _uleb128_t imatcher;
-                                        // Get the relative offset to the {...}?
-                                        cur_ptr = read_uleb128(cur_ptr, &imatcher);
-
-                                        _Unwind_Reason_Code (*matcher)(exception_t *) =
-                                                MATCHER_FROM_CONTEXT(context);
-                                        int index = matcher(shared_stack.current_exception);
-                                        _Unwind_Reason_Code ret = (0 == index)
-                                                ? _URC_CONTINUE_UNWIND : _URC_HANDLER_FOUND;
-                                        shared_stack.current_handler_index = index;
-
-                                        // Based on the return value, check if we matched the exception
-                                        if( ret == _URC_HANDLER_FOUND) {
-                                                __cfaabi_dbg_print_safe(" handler found\n");
-                                        } else {
-                                                __cfaabi_dbg_print_safe(" no handler\n");
-                                        }
-                                        return ret;
+                // Check for what we must do:
+                if ( 0 == callsite_landing_pad ) {
+                        // Nothing to do, move along
+                        __cfadbg_print_safe(exception, " no landing pad");
+                } else if (actions & _UA_SEARCH_PHASE) {
+                        // In search phase, these means we found a potential handler we must check.
+
+                        // We have arbitrarily decided that 0 means nothing to do and 1 means there is
+                        // a potential handler. This doesn't seem to conflict the gcc default behavior.
+                        if (callsite_action != 0) {
+                                // Now we want to run some code to see if the handler matches
+                                // This is the tricky part where we want to the power to run arbitrary code
+                                // However, generating a new exception table entry and try routine every time
+                                // is way more expansive than we might like
+                                // The information we have is :
+                                //  - The GR (Series of registers)
+                                //    GR1=GP Global Pointer of frame ref by context
+                                //  - The instruction pointer
+                                //  - The instruction pointer info (???)
+                                //  - The CFA (Canonical Frame Address)
+                                //  - The BSP (Probably the base stack pointer)
+
+                                // The current apprach uses one exception table entry per try block
+                                _uleb128_t imatcher;
+                                // Get the relative offset to the {...}?
+                                cur_ptr = read_uleb128(cur_ptr, &imatcher);
+
+#                               if defined( __x86_64 )
+                                _Unwind_Word match_pos = _Unwind_GetCFA(unwind_context) + 8;
+#                               elif defined( __i386 )
+                                _Unwind_Word match_pos = _Unwind_GetCFA(unwind_context) + 24;
+#                               endif
+                                int (*matcher)(exception_t *) = *(int(**)(exception_t *))match_pos;
+
+                                int index = matcher(context->current_exception);
+                                _Unwind_Reason_Code ret = (0 == index)
+                                        ? _URC_CONTINUE_UNWIND : _URC_HANDLER_FOUND;
+                                context->current_handler_index = index;
+
+                                // Based on the return value, check if we matched the exception
+                                if (ret == _URC_HANDLER_FOUND) {
+                                        __cfadbg_print_safe(exception, " handler found\n");
+                                } else {
+                                        __cfadbg_print_safe(exception, " no handler\n");
                                 }
-
-                                // This is only a cleanup handler, ignore it
-                                __cfaabi_dbg_print_safe(" no action");
+                                return ret;
                         }
-                        else if (actions & _UA_CLEANUP_PHASE) {
-
-                                if( (callsite_action != 0) && !(actions & _UA_HANDLER_FRAME) ){
-                                        // If this is a potential exception handler
-                                        // but not the one that matched the exception in the seach phase,
-                                        // just ignore it
-                                        goto UNWIND;
-                                }
-
-                                // We need to run some clean-up or a handler
-                                // These statment do the right thing but I don't know any specifics at all
-                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(0), (_Unwind_Ptr) unwind_exception );
-                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(1), 0 );
-
-                                // I assume this sets the instruction pointer to the adress of the landing pad
-                                // It doesn't actually set it, it only state the value that needs to be set once we return _URC_INSTALL_CONTEXT
-                                _Unwind_SetIP( context, ((lsd_info.LPStart) + (callsite_landing_pad)) );
-
-                                __cfaabi_dbg_print_safe(" action\n");
-
-                                // Return have some action to run
-                                return _URC_INSTALL_CONTEXT;
+
+                        // This is only a cleanup handler, ignore it
+                        __cfadbg_print_safe(exception, " no action");
+                } else {
+                        // In clean-up phase, no destructors here but this could be the handler.
+
+                        if ( (callsite_action != 0) && !(actions & _UA_HANDLER_FRAME) ){
+                                // If this is a potential exception handler
+                                // but not the one that matched the exception in the seach phase,
+                                // just ignore it
+                                goto UNWIND;
                         }
+
+                        // We need to run some clean-up or a handler
+                        // These statment do the right thing but I don't know any specifics at all
+                        _Unwind_SetGR( unwind_context, __builtin_eh_return_data_regno(0),
+                                (_Unwind_Ptr)unwind_exception );
+                        _Unwind_SetGR( unwind_context, __builtin_eh_return_data_regno(1), 0 );
+
+                        // I assume this sets the instruction pointer to the adress of the landing pad
+                        // It doesn't actually set it, it only state the value that needs to be set once we
+                        // return _URC_INSTALL_CONTEXT
+                        _Unwind_SetIP( unwind_context, ((lsd_info.LPStart) + (callsite_landing_pad)) );
+
+                        __cfadbg_print_safe(exception, " action\n");
+
+                        // Return have some action to run
+                        return _URC_INSTALL_CONTEXT;
                 }
-
-                // Nothing to do, move along
-                __cfaabi_dbg_print_safe(" no landing pad");
         }
         // No handling found
-        __cfaabi_dbg_print_safe(" table end reached\n");
+        __cfadbg_print_safe(exception, " table end reached");
 
         UNWIND:
-        __cfaabi_dbg_print_safe(" unwind\n");
+        __cfadbg_print_safe(exception, " unwind\n");
 
         // Keep unwinding the stack
         return _URC_CONTINUE_UNWIND;
 }
+
+#pragma GCC push_options
+#pragma GCC optimize(0)
 
 // Try statements are hoisted out see comments for details. While this could probably be unique
 // and simply linked from libcfa but there is one problem left, see the exception table for details
 __attribute__((noinline))
-void __cfaabi_ehm__try_terminate(void (*try_block)(),
+void __cfaehm_try_terminate(void (*try_block)(),
                 void (*catch_block)(int index, exception_t * except),
                 __attribute__((unused)) int (*match_block)(exception_t * except)) {
@@ -419 +456 @@
         //! printf("%p %p %p %p\n", &try_block, &catch_block, &match_block, &xy);
 
-        // Setup statments: These 2 statments won't actually result in any code, they only setup global tables.
-        // However, they clobber gcc cancellation support from gcc.  We can replace the personality routine but
-        // replacing the exception table gcc generates is not really doable, it generates labels based on how the
-        // assembly works.
-
         // Setup the personality routine and exception table.
+        // Unforturnately these clobber gcc cancellation support which means we can't get access to
+        // the attribute cleanup tables at the same time. We would have to inspect the assembly to
+        // create a new set ourselves.
 #ifdef __PIC__
         asm volatile (".cfi_personality 0x9b,CFA.ref.__gcfa_personality_v0");
@@ -449 +484 @@
         // Label which defines the end of the area for which the handler is setup.
         asm volatile (".TRYEND:");
-        // Label which defines the start of the exception landing pad.  Basically what is called when the exception is
-        // caught.  Note, if multiple handlers are given, the multiplexing should be done by the generated code, not the
-        // exception runtime.
+        // Label which defines the start of the exception landing pad. Basically what is called when
+        // the exception is caught. Note, if multiple handlers are given, the multiplexing should be
+        // done by the generated code, not the exception runtime.
         asm volatile (".CATCH:");
 
         // Exception handler
-        catch_block( shared_stack.current_handler_index,
-                     shared_stack.current_exception );
+        // Note: Saving the exception context on the stack breaks termination exceptions.
+        catch_block( this_exception_context()->current_handler_index,
+                     this_exception_context()->current_exception );
 }
 
@@ -464 +500 @@
 
 #ifdef __PIC__
-#if defined( __i386 ) || defined( __x86_64 )
 asm (
         // HEADER
@@ -481 +516 @@
         // handler landing pad offset and 1 (action code, gcc seems to use 0).
         ".LLSDACSBCFA2:\n"
-        "       .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n"
+        "       .uleb128 .TRYSTART-__cfaehm_try_terminate\n"
         "       .uleb128 .TRYEND-.TRYSTART\n"
-        "       .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n"
+        "       .uleb128 .CATCH-__cfaehm_try_terminate\n"
         "       .uleb128 1\n"
         ".LLSDACSECFA2:\n"
         // TABLE FOOTER
         "       .text\n"
-        "       .size   __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n"
+        "       .size   __cfaehm_try_terminate, .-__cfaehm_try_terminate\n"
 );
 
@@ -507 +542 @@
         "       .quad __gcfa_personality_v0\n"
 #else // then __i386
-        "   .long __gcfa_personality_v0\n"
+        "       .long __gcfa_personality_v0\n"
 #endif
 );
-#else
-#error Exception Handling: unknown architecture for position independent code.
-#endif // __i386 || __x86_64
 #else // __PIC__
-#if defined( __i386 ) || defined( __x86_64 )
 asm (
         // HEADER
@@ -529 +560 @@
         ".LLSDACSBCFA2:\n"
         //      Handled area start (relative to start of function)
-        "       .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n"
+        "       .uleb128 .TRYSTART-__cfaehm_try_terminate\n"
         //      Handled area length
         "       .uleb128 .TRYEND-.TRYSTART\n"
         //      Handler landing pad address (relative to start of function)
-        "       .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n"
+        "       .uleb128 .CATCH-__cfaehm_try_terminate\n"
         //      Action code, gcc seems to always use 0.
         "       .uleb128 1\n"
@@ -539 +570 @@
         ".LLSDACSECFA2:\n"
         "       .text\n"
-        "       .size   __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n"
+        "       .size   __cfaehm_try_terminate, .-__cfaehm_try_terminate\n"
         "       .ident  \"GCC: (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901\"\n"
         "       .section        .note.GNU-stack,\"x\",@progbits\n"
 );
-#else
-#error Exception Handling: unknown architecture for position dependent code.
-#endif // __i386 || __x86_64
 #endif // __PIC__