Fix incorrect exception handling on aarch64

Fixes #3874

src/libponyrt/lang/lsda.c

@@ -216,7 +216,9 @@ static bool lsda_init(lsda_t* lsda, exception_context_t* context)
   return true;
 }
 
-bool ponyint_lsda_scan(exception_context_t* context, uintptr_t* lp)
+bool ponyint_lsda_scan(uintptr_t* ttype_index,
+  exception_context_t* context,
+  uintptr_t* lp)
 {
   lsda_t lsda;
 
@@ -231,8 +233,11 @@ bool ponyint_lsda_scan(exception_context_t* context, uintptr_t* lp)
     uintptr_t length = read_encoded_ptr(&p, lsda.call_site_encoding);
     uintptr_t landing_pad = read_encoded_ptr(&p, lsda.call_site_encoding);
 
-    // Pony ignores the action index, since it uses only cleanup landing pads.
-    read_uleb128(&p);
+    uintptr_t action_index = read_uleb128(&p);
+
+    const uint8_t* action = lsda.action_table + (action_index - 1);
+    int64_t tti = read_sleb128(&action);
+    ttype_index = (uintptr_t*)&tti;
 
     if((start <= lsda.ip_offset) && (lsda.ip_offset < (start + length)))
     {

src/libponyrt/lang/lsda.h

@@ -18,7 +18,9 @@ typedef struct _Unwind_Context exception_context_t;
 typedef DISPATCHER_CONTEXT exception_context_t;
 #endif
 
-bool ponyint_lsda_scan(exception_context_t* context, uintptr_t* lp);
+bool ponyint_lsda_scan(uintptr_t* ttype_index,
+  exception_context_t* context,
+  uintptr_t* lp);
 
 PONY_EXTERN_C_END
 

src/libponyrt/lang/posix_except.c

@@ -39,12 +39,13 @@ PONY_API void pony_error()
   abort();
 }
 
-static void set_registers(struct _Unwind_Exception* exception,
+static void set_registers(uintptr_t ttype_index,
+  struct _Unwind_Exception* exception,
   struct _Unwind_Context* context)
 {
   _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
     (uintptr_t)exception);
-  _Unwind_SetGR(context, __builtin_eh_return_data_regno(1), 0);
+  _Unwind_SetGR(context, __builtin_eh_return_data_regno(1), ttype_index);
   _Unwind_SetIP(context, landing_pad);
 }
 
@@ -79,7 +80,8 @@ PONY_API _Unwind_Reason_Code ponyint_personality_v0(_Unwind_State state,
   {
     case _US_VIRTUAL_UNWIND_FRAME:
     {
-      if(!ponyint_lsda_scan(context, &landing_pad))
+      uintptr_t ignore;
+      if(!ponyint_lsda_scan(&ignore, context, &landing_pad))
         return continue_unwind(exception, context);
 
       // Save r13.
@@ -133,10 +135,13 @@ PONY_API _Unwind_Reason_Code ponyint_personality_v0(int version,
   if(ex_class != PONY_EXCEPTION_CLASS)
     return _URC_CONTINUE_UNWIND;
 
+  uintptr_t ttype_index;
+  bool scan_result = ponyint_lsda_scan(&ttype_index, context, &landing_pad);
+
   // The search phase sets up the landing pad.
   if(actions & _UA_SEARCH_PHASE)
   {
-    if(!ponyint_lsda_scan(context, &landing_pad))
+    if(!scan_result)
       return _URC_CONTINUE_UNWIND;
 
     return _URC_HANDLER_FOUND;
@@ -148,7 +153,7 @@ PONY_API _Unwind_Reason_Code ponyint_personality_v0(int version,
       return _URC_CONTINUE_UNWIND;
 
     // No need to search again, just set the registers.
-    set_registers(exception, context);
+    set_registers(ttype_index, exception, context);
     return _URC_INSTALL_CONTEXT;
   }
 

src/libponyrt/lang/win_except.c

@@ -93,7 +93,8 @@ PONY_API EXCEPTION_DISPOSITION ponyint_personality_v0(
   if(!(ExcRecord->ExceptionFlags &
     (EXCEPTION_UNWINDING | EXCEPTION_EXIT_UNWIND)))
   {
-    if(!ponyint_lsda_scan(DispatcherContext, &landing_pad))
+    uintptr_t ignore;
+    if(!ponyint_lsda_scan(&ignore, DispatcherContext, &landing_pad))
       return ExceptionContinueSearch;
 
     RtlUnwindEx(EstablisherFrame, (PVOID)landing_pad, ExcRecord,

test/libponyc-run/regression-3874-case-1/main.pony

@@ -0,0 +1,14 @@
+actor Main
+  new create(env: Env) =>
+    foo("hello")
+
+  fun foo(s: String) =>
+    try
+      one(s)
+      error
+    else
+      one(s)
+    end
+
+  fun one(s: String) =>
+    s.clone()

test/libponyc-run/regression-3874-case-2/main.pony

@@ -0,0 +1,17 @@
+actor Main
+  let _out: OutStream
+
+  new create(env: Env) =>
+    _out = env.out
+    foo("hello")
+
+  fun foo(s: String) =>
+    try
+      one("h")
+      error
+    else
+      one("e")
+    end
+
+  fun one(s: String) =>
+    _out.print(s)