[Devel] [RFC] proposed patch for some segfaults encountered

[Al Stone <ahs3 at redhat.com>]

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It's not clear to me that this is the correct way to handle a segfault that
was reported to me via Fedora.

Using the ssdt9.dat file attached, a simple "iasl -d ssdt9.dat" will segfault
around calls to AcpiDmPromoteTarget -- and it turns out that the Target pointer
being passed into that function was sometimes null but not being checked in the
calling function, AcpiDmCheckForSymbolicOpcode.  So, this patch adds in some
checks for null pointers and can now get through this particular problem.

However, I did not study AcpiDmCheckForSymbolicOpcode long enough to determine
if the Target pointer in that function should or should not ever be null.  So,
this patch fixes this issue, but it may not be the proper long term solution.

-- 
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Red Hat, Inc.
ahs3(a)redhat.com
-----------------------------------

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diff -Naur acpica-unix2-20150515.orig/source/components/disassembler/dmcstyle.c acpica-unix2-20150515/source/components/disassembler/dmcstyle.c
--- acpica-unix2-20150515.orig/source/components/disassembler/dmcstyle.c	2015-06-01 14:32:51.769218887 -0600
+++ acpica-unix2-20150515/source/components/disassembler/dmcstyle.c	2015-06-01 14:37:38.973898839 -0600
@@ -407,7 +407,7 @@
         {
             AcpiDmPromoteTarget (Op, Target);
 
-            if (!Target->Common.OperatorSymbol)
+            if (Target && !Target->Common.OperatorSymbol)
             {
                 Target->Common.OperatorSymbol = " = ";
             }
@@ -425,7 +425,7 @@
         Target = Child1->Common.Next;
         AcpiDmPromoteTarget (Op, Target);
 
-        if (!Target->Common.OperatorSymbol)
+        if (Target && !Target->Common.OperatorSymbol)
         {
             Target->Common.OperatorSymbol = " = ";
         }
@@ -446,7 +446,10 @@
             /* Valid target, not a placeholder */
 
             AcpiDmPromoteTarget (Op, Target);
-            Target->Common.OperatorSymbol = " = ~";
+	    if (Target)
+	    {
+            	Target->Common.OperatorSymbol = " = ~";
+	    }
         }
         else
         {