[DWARFYAML][debug_info] Fix array index out of bounds error

[Higuoxing]

Summary

This patch is trying to fix the array index out of bounds error. I observed it in (https://reviews.llvm.org/harbormaster/unit/view/99638/).

[Higuoxing]

I think this isn't a good approach. I will upload another revision.

[Higuoxing]

This patch gives a quick fix to the index-out-of-bounds error.

[jhenderson]

Seems reasonable to me.

I assume one of your other changes includes the test coverage for this? Could you remove the failing test case from that change, and add this change as a child, with the removed test case included? That way, your fix has an associated test case from the start. In other words, I'd reorder your dependencies: first D82073 (minus failing test) then D82139 (with test).

[Higuoxing]

Add one test.

[jhenderson]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-info.yaml

558

Do you need a {{$}} on the end of this line? If there's more output on the same line, the test will continue to pass. Alternatively, use --match-full-lines

[Higuoxing]

Use --match-full-lines.

llvm/test/tools/yaml2obj/ELF/DWARF/debug-info.yaml

558

Thanks!

[jhenderson]

LGTM.

[MaskRay]

Looks great!

llvm/lib/ObjectYAML/DWARFVisitor.cpp

49

Use empty()

[MaskRay]

I removed NFC from the subject: the patch is no longer NFC due to the code change. Please adjust your local commit (arc amend should do it)

[Higuoxing]

In D82139#2103913, @MaskRay wrote:

I removed NFC from the subject: the patch is no longer NFC due to the code change. Please adjust your local commit (arc amend should do it)

Thanks!

llvm/lib/ObjectYAML/DWARFVisitor.cpp

static unsigned getRefSize(const DWARFYAML::Unit &Unit) {
   if (Unit.Version == 2)
     return Unit.AddrSize;
   return getOffsetSize(Unit);
 }
 
 template <typename T> void DWARFYAML::VisitorImpl<T>::traverseDebugInfo() {
   for (auto &Unit : DebugInfo.CompileUnits) {
     onStartCompileUnit(Unit);
+    if (Unit.Entries.empty())
+      continue;
     auto FirstAbbrevCode = Unit.Entries[0].AbbrCode;
 
     for (auto &Entry : Unit.Entries) {
       onStartDIE(Unit, Entry);
       if (Entry.AbbrCode == 0u)
         continue;
       auto &Abbrev = DebugInfo.AbbrevDecls[Entry.AbbrCode - FirstAbbrevCode];
       auto FormVal = Entry.Values.begin();

llvm/test/tools/yaml2obj/ELF/DWARF/debug-info.yaml

- Length:
         TotalLength: 0x1234
       Version:    5
       UnitType:   DW_UT_type
       AbbrOffset: 0x1234
       AddrSize:   4
       Entries:
         - AbbrCode: 0
           Values:   []
+
+## h) Test that yaml2obj doesn't crash when the 'Entries' of a compilation unit is empty.
+
+# RUN: yaml2obj --docnum=8 %s -o %t8.o
+# RUN: llvm-readelf --hex-dump=.debug_info %t8.o | \
+# RUN:   FileCheck %s --check-prefix=EMPTY-ENTRIES --match-full-lines
+
+#       EMPTY-ENTRIES: Hex dump of section '.debug_info':
+#  EMPTY-ENTRIES-NEXT: 0x00000000 34120000 05000204 34120000 4.......4...
+# EMPTY-ENTRIES-EMPTY:
+##                                ^- 'Entries' is empty
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+DWARF:
+  debug_info:
+    - Length:
+        TotalLength: 0x1234
+      Version:    5
+      UnitType:   DW_UT_type
+      AbbrOffset: 0x1234
+      AddrSize:   4
+      Entries:    []