[Lldb-commits] [PATCH] D77108: [lldb/DWARF] Fix evaluator crash when accessing empty stack

Med Ismail Bennani via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Mon Mar 30 18:03:07 PDT 2020

mib created this revision.
mib added a reviewer: aprantl.
mib added a project: LLDB.
Herald added a subscriber: lldb-commits.

This patch fixes a crash that happens on the DWARF expression evaluator
when trying to access the top of the stack while it's empty.

Signed-off-by: Med Ismail Bennani <medismail.bennani at gmail.com>

  rG LLVM Github Monorepo



Index: lldb/unittests/Expression/DWARFExpressionTest.cpp
--- lldb/unittests/Expression/DWARFExpressionTest.cpp
+++ lldb/unittests/Expression/DWARFExpressionTest.cpp
@@ -234,6 +234,10 @@
+TEST(DWARFExpression, DW_OP_stack_value) {
+  EXPECT_THAT_ERROR(Evaluate({DW_OP_stack_value}).takeError(), llvm::Failed());
 TEST(DWARFExpression, DW_OP_piece) {
   EXPECT_THAT_EXPECTED(Evaluate({DW_OP_const2u, 0x11, 0x22, DW_OP_piece, 2,
                                  DW_OP_const2u, 0x33, 0x44, DW_OP_piece, 2}),
Index: lldb/source/Expression/DWARFExpression.cpp
--- lldb/source/Expression/DWARFExpression.cpp
+++ lldb/source/Expression/DWARFExpression.cpp
@@ -2318,6 +2318,12 @@
     // rather is a constant value.  The value from the top of the stack is the
     // value to be used.  This is the actual object value and not the location.
     case DW_OP_stack_value:
+      if (stack.empty()) {
+        if (error_ptr)
+          error_ptr->SetErrorString(
+              "Expression stack needs at least 1 item for DW_OP_stack_value.");
+        return false;
+      }

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