[IRGen] Check if VTable isn't a nullptr.

Davide Italiano · Davide Italiano · commit b0a419b297bd · 2020-07-14T16:05:06.000-07:00
Fixes a ubsan error on the lldb bots

runtime error: member call on null pointer of type 'swift::SILVTable'
undefined-behavior lib/IRGen/GenMeta.cpp:5107:24
diff --git a/lib/IRGen/ClassMetadataVisitor.h b/lib/IRGen/ClassMetadataVisitor.h
@@ -171,7 +171,7 @@ template <class Impl> class ClassMetadataVisitor
   friend SILVTableVisitor<Impl>;
   void addMethod(SILDeclRef declRef) {
     // Does this method require a reified runtime vtable entry?
-    if (methodRequiresReifiedVTableEntry(IGM, VTable, declRef)) {
+    if (!VTable || methodRequiresReifiedVTableEntry(IGM, VTable, declRef)) {
       asImpl().addReifiedVTableEntry(declRef);
     }
   }
diff --git a/lib/IRGen/GenMeta.cpp b/lib/IRGen/GenMeta.cpp
@@ -1440,7 +1440,7 @@ namespace {
     }
 
     void addMethod(SILDeclRef fn) {
-      if (methodRequiresReifiedVTableEntry(IGM, VTable, fn)) {
+      if (!VTable || methodRequiresReifiedVTableEntry(IGM, VTable, fn)) {
         VTableEntries.push_back(fn);
       } else if (getType()->getEffectiveAccess() >= AccessLevel::Public) {
         // Emit a stub method descriptor and lookup function for nonoverridden

Original file line number	Diff line number	Diff line change
`@@ -171,7 +171,7 @@ template <class Impl> class ClassMetadataVisitor`
`171`	`171`	`friend SILVTableVisitor<Impl>;`
`172`	`172`	`void addMethod(SILDeclRef declRef) {`
`173`	`173`	`// Does this method require a reified runtime vtable entry?`
`174`		`- if (methodRequiresReifiedVTableEntry(IGM, VTable, declRef)) {`
	`174`	`+ if (!VTable \|\| methodRequiresReifiedVTableEntry(IGM, VTable, declRef)) {`
`175`	`175`	`asImpl().addReifiedVTableEntry(declRef);`
`176`	`176`	`}`
`177`	`177`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1440,7 +1440,7 @@ namespace {`
`1440`	`1440`	`}`
`1441`	`1441`
`1442`	`1442`	`void addMethod(SILDeclRef fn) {`
`1443`		`- if (methodRequiresReifiedVTableEntry(IGM, VTable, fn)) {`
	`1443`	`+ if (!VTable \|\| methodRequiresReifiedVTableEntry(IGM, VTable, fn)) {`
`1444`	`1444`	`VTableEntries.push_back(fn);`
`1445`	`1445`	`} else if (getType()->getEffectiveAccess() >= AccessLevel::Public) {`
`1446`	`1446`	`// Emit a stub method descriptor and lookup function for nonoverridden`