[gcc r12-3989] libphobos: Select the appropriate exception handler in getClassInfo

[gcc r12-3989] libphobos: Select the appropriate exception handler in getClassInfo

[Iain Buclaw]

https://gcc.gnu.org/g:8088a33df5f62fd6416fb8cb158b791e639aa707

commit r12-3989-g8088a33df5f62fd6416fb8cb158b791e639aa707
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Sat Sep 25 23:18:53 2021 +0200

    libphobos: Select the appropriate exception handler in getClassInfo
    
    This is analogous to __gdc_personality, which ignores in-flight
    exceptions that we haven't collided with yet.
    
    libphobos/ChangeLog:
    
            * libdruntime/gcc/deh.d (ExceptionHeader.getClassInfo): Move to...
            (getClassInfo): ...here as free function.  Add lsda parameter.
            (scanLSDA): Pass lsda to actionTableLookup.
            (actionTableLookup): Add lsda parameter, pass to getClassInfo.
            (__gdc_personality): Remove currentCfa variable.

Diff:
---
 libphobos/libdruntime/gcc/deh.d | 74 ++++++++++++++++++++++++-----------------
 1 file changed, 44 insertions(+), 30 deletions(-)

diff --git a/libphobos/libdruntime/gcc/deh.d b/libphobos/libdruntime/gcc/deh.d
index a7eb37cfd9e..ba57fed38dc 100644
--- a/libphobos/libdruntime/gcc/deh.d
+++ b/libphobos/libdruntime/gcc/deh.d
@@ -279,26 +279,6 @@ struct ExceptionHeader
         }
     }
 
-    /**
-     * Look at the chain of inflight exceptions and pick the class type that'll
-     * be looked for in catch clauses.
-     */
-    static ClassInfo getClassInfo(_Unwind_Exception* unwindHeader) @nogc
-    {
-        ExceptionHeader* eh = toExceptionHeader(unwindHeader);
-        // The first thrown Exception at the top of the stack takes precedence
-        // over others that are inflight, unless an Error was thrown, in which
-        // case, we search for error handlers instead.
-        Throwable ehobject = eh.object;
-        for (ExceptionHeader* ehn = eh.next; ehn; ehn = ehn.next)
-        {
-            Error e = cast(Error)ehobject;
-            if (e is null || (cast(Error)ehn.object) !is null)
-                ehobject = ehn.object;
-        }
-        return ehobject.classinfo;
-    }
-
     /**
      * Convert from pointer to unwindHeader to pointer to ExceptionHeader
      * that it is embedded inside of.
@@ -666,7 +646,7 @@ _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class excepti
     {
         // Otherwise we have a catch handler or exception specification.
         handler = actionTableLookup(actions, unwindHeader, actionRecord,
-                                    exceptionClass, TTypeBase,
+                                    lsda, exceptionClass, TTypeBase,
                                     TType, TTypeEncoding,
                                     saw_handler, saw_cleanup);
     }
@@ -694,7 +674,8 @@ _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class excepti
  * Look up and return the handler index of the classType in Action Table.
  */
 int actionTableLookup(_Unwind_Action actions, _Unwind_Exception* unwindHeader,
-                      const(ubyte)* actionRecord, _Unwind_Exception_Class exceptionClass,
+                      const(ubyte)* actionRecord, const(ubyte)* lsda,
+                      _Unwind_Exception_Class exceptionClass,
                       _Unwind_Ptr TTypeBase, const(ubyte)* TType,
                       ubyte TTypeEncoding,
                       out bool saw_handler, out bool saw_cleanup)
@@ -702,7 +683,7 @@ int actionTableLookup(_Unwind_Action actions, _Unwind_Exception* unwindHeader,
     ClassInfo thrownType;
     if (isGdcExceptionClass(exceptionClass))
     {
-        thrownType = ExceptionHeader.getClassInfo(unwindHeader);
+        thrownType = getClassInfo(unwindHeader, lsda);
     }
 
     while (1)
@@ -778,6 +759,41 @@ int actionTableLookup(_Unwind_Action actions, _Unwind_Exception* unwindHeader,
     return 0;
 }
 
+/**
+ * Look at the chain of inflight exceptions and pick the class type that'll
+ * be looked for in catch clauses.
+ */
+ClassInfo getClassInfo(_Unwind_Exception* unwindHeader,
+                       const(ubyte)* currentLsd) @nogc
+{
+    ExceptionHeader* eh = ExceptionHeader.toExceptionHeader(unwindHeader);
+    // The first thrown Exception at the top of the stack takes precedence
+    // over others that are inflight, unless an Error was thrown, in which
+    // case, we search for error handlers instead.
+    Throwable ehobject = eh.object;
+    for (ExceptionHeader* ehn = eh.next; ehn; ehn = ehn.next)
+    {
+        const(ubyte)* nextLsd = void;
+        _Unwind_Ptr nextLandingPad = void;
+        _Unwind_Word nextCfa = void;
+        int nextHandler = void;
+
+        ExceptionHeader.restore(&ehn.unwindHeader, nextHandler, nextLsd, nextLandingPad, nextCfa);
+
+        // Don't combine when the exceptions are from different functions.
+        if (currentLsd != nextLsd)
+            break;
+
+        Error e = cast(Error)ehobject;
+        if (e is null || (cast(Error)ehn.object) !is null)
+        {
+            currentLsd = nextLsd;
+            ehobject = ehn.object;
+        }
+    }
+    return ehobject.classinfo;
+}
+
 /**
  * Called when the personality function has found neither a cleanup or handler.
  * To support ARM EABI personality routines, that must also unwind the stack.
@@ -934,16 +950,15 @@ private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
         // current object onto the end of the prevous object.
         ExceptionHeader* eh = ExceptionHeader.toExceptionHeader(unwindHeader);
         auto currentLsd = lsda;
-        auto currentCfa = cfa;
         bool bypassed = false;
 
         while (eh.next)
         {
             ExceptionHeader* ehn = eh.next;
-            const(ubyte)* nextLsd;
-            _Unwind_Ptr nextLandingPad;
-            _Unwind_Word nextCfa;
-            int nextHandler;
+            const(ubyte)* nextLsd = void;
+            _Unwind_Ptr nextLandingPad = void;
+            _Unwind_Word nextCfa = void;
+            int nextHandler = void;
 
             ExceptionHeader.restore(&ehn.unwindHeader, nextHandler, nextLsd, nextLandingPad, nextCfa);
 
@@ -952,14 +967,13 @@ private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
             {
                 // We found an Error, bypass the exception chain.
                 currentLsd = nextLsd;
-                currentCfa = nextCfa;
                 eh = ehn;
                 bypassed = true;
                 continue;
             }
 
             // Don't combine when the exceptions are from different functions.
-            if (currentLsd != nextLsd && currentCfa != nextCfa)
+            if (currentLsd != nextLsd)
                 break;
 
             // Add our object onto the end of the existing chain.