llvm-undname: Fix an assert-on-invalid

Found by oss-fuzz, fixes issues 12428 and 12429 on oss-fuzz.

Differential Revision: https://reviews.llvm.org/D60204

llvm-svn: 357647

2 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Demangle/MicrosoftDemangle.cpp b/llvm/lib/Demangle/MicrosoftDemangle.cpp
index b8e39c41527..b4e5cef7ac5 100644
--- a/llvm/lib/Demangle/MicrosoftDemangle.cpp
+++ b/llvm/lib/Demangle/MicrosoftDemangle.cpp
@@ -466,6 +466,10 @@ IdentifierNode *
 Demangler::demangleFunctionIdentifierCode(StringView &MangledName) {
   assert(MangledName.startsWith('?'));
   MangledName = MangledName.dropFront();
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
 
   if (MangledName.consumeFront("__"))
     return demangleFunctionIdentifierCode(
@@ -637,6 +641,7 @@ translateIntrinsicFunctionCode(char CH, FunctionIdentifierCodeGroup Group) {
 IdentifierNode *
 Demangler::demangleFunctionIdentifierCode(StringView &MangledName,
                                           FunctionIdentifierCodeGroup Group) {
+  assert(!MangledName.empty());
   switch (Group) {
   case FunctionIdentifierCodeGroup::Basic:
     switch (char CH = MangledName.popFront()) {
diff --git a/llvm/test/Demangle/invalid-manglings.test b/llvm/test/Demangle/invalid-manglings.test
index 6883a46d8d3..af919282bb8 100644
--- a/llvm/test/Demangle/invalid-manglings.test
+++ b/llvm/test/Demangle/invalid-manglings.test
@@ -14,3 +14,8 @@
 ; CHECK-EMPTY:
 ; CHECK-NEXT: ?@@8
 ; CHECK-NEXT: error: Invalid mangled name
+
+??
+; CHECK-EMPTY:
+; CHECK-NEXT: ??
+; CHECK-NEXT: error: Invalid mangled name