[llvm-dwarfdump] Add a null-check in prettyPrintBaseTypeRef.

[mgschossmann]

Fixes #93104

Prevent a crash by only printing DWARFUnit-unaware information in cases in which DWARFUnit* U is nullptr.

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@llvm/pr-subscribers-debuginfo

Author: None (mgschossmann)

Changes

Fixes #93104

Prevent a crash by only printing DWARFUnit-unaware information in cases in which DWARFUnit* U is nullptr.

---

Full diff: https://github.com/llvm/llvm-project/pull/93156.diff

1 Files Affected:

• (modified) llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp (+14-10)

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp b/llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp
index 87a4fc78ceb19..0c28701360b3c 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp
@@ -240,17 +240,21 @@ static void prettyPrintBaseTypeRef(DWARFUnit *U, raw_ostream &OS,
                                    ArrayRef<uint64_t> Operands,
                                    unsigned Operand) {
   assert(Operand < Operands.size() && "operand out of bounds");
-  auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
-  if (Die && Die.getTag() == dwarf::DW_TAG_base_type) {
-    OS << " (";
-    if (DumpOpts.Verbose)
-      OS << format("0x%08" PRIx64 " -> ", Operands[Operand]);
-    OS << format("0x%08" PRIx64 ")", U->getOffset() + Operands[Operand]);
-    if (auto Name = dwarf::toString(Die.find(dwarf::DW_AT_name)))
-      OS << " \"" << *Name << "\"";
+  if (U) {
+    auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
+    if (Die && Die.getTag() == dwarf::DW_TAG_base_type) {
+      OS << " (";
+      if (DumpOpts.Verbose)
+        OS << format("0x%08" PRIx64 " -> ", Operands[Operand]);
+      OS << format("0x%08" PRIx64 ")", U->getOffset() + Operands[Operand]);
+      if (auto Name = dwarf::toString(Die.find(dwarf::DW_AT_name)))
+        OS << " \"" << *Name << "\"";
+    } else {
+      OS << format(" <invalid base_type ref: 0x%" PRIx64 ">",
+                   Operands[Operand]);
+    }
   } else {
-    OS << format(" <invalid base_type ref: 0x%" PRIx64 ">",
-                 Operands[Operand]);
+    OS << format(" <base_type ref: 0x%" PRIx64 ">", Operands[Operand]);
   }
 }
 

[JDevlieghere]

Can we add a test for this?

[mgschossmann]

I have now found a small program (https://godbolt.org/z/eKcvY6caW) that, when compiled with gcc, results in a .debug_loclists section containing such a base type reference, which currently crashes dwarfdump.

I can try to add a test case which is based on this.

[dwblaikie]

Rather than a checked-in binary, could you use assembly code instead? Perhaps using the new https://llvm.org/docs/TestingGuide.html#elaborated-tests functionality

[mgschossmann]

Unfortunately, I am not aware of any way to reliably generate specific .debug_loclists contents (that include a base type reference) from within the testfile.

[dwblaikie]

Unfortunately, I am not aware of any way to reliably generate specific .debug_loclists contents (that include a base type reference) from within the testfile.

Where'd you get the binary from? Could you rerun that compilation with -S to get assembly code instead, then check that in (and assemble it with llvm-mc inside the test - you can see other symbolizer tests that do this in the related directories)

[dwblaikie]

Looks good, thanks!

[mgschossmann]

Thanks for the approval. As I do not have write access, could you please commit it for me?

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