[llvm] [dwarf] Fix DWARFListTableHeader::getOffsetEntry off-by-one

[jankratochvil]

Summary

D98289 was erroneously reporting invalid range list offset 0x20110 instead of invalid range list table index 0.

[labath]

llvm/unittests/DebugInfo/DWARF/DWARFListTableTest.cpp

95–96

I think EXPECT_EQ(Offset0, uint64_t(4)); (note missing *) should be enough.

[jankratochvil]

llvm/unittests/DebugInfo/DWARF/DWARFListTableTest.cpp

95–96

Nice, I did not know (even std::optional).

llvm/include/llvm/DebugInfo/DWARF/DWARFListTable.h

case dwarf::DwarfFormat::DWARF64:
       return 20;
     }
     llvm_unreachable("Invalid DWARF format (expected DWARF32 or DWARF64");
   }
 
   void dump(DataExtractor Data, raw_ostream &OS,
             DIDumpOptions DumpOpts = {}) const;
   Optional<uint64_t> getOffsetEntry(DataExtractor Data, uint32_t Index) const {
-    if (Index > HeaderData.OffsetEntryCount)
+    if (Index >= HeaderData.OffsetEntryCount)
       return None;
 
     return getOffsetEntry(Data, getHeaderOffset() + getHeaderSize(Format), Format, Index);
   }
 
   static Optional<uint64_t> getOffsetEntry(DataExtractor Data,
                                            uint64_t OffsetTableOffset,
                                            dwarf::DwarfFormat Format,

llvm/unittests/DebugInfo/DWARF/DWARFListTableTest.cpp

EXPECT_THAT_ERROR(
       FailedWithMessage(".debug_rnglists table at offset 0x0 has too small "
                         "length (0x6) to contain a complete header"));
   // length() is expected to return the full length of the set if the unit
   // length field is read, even if an error occurred during the parsing,
   // to allow skipping the current set and continue parsing from the next one.
   EXPECT_EQ(Header.length(), 6u);
 }
 
+TEST(DWARFListTableHeader, OffsetEntryCount) {
+  static const char SecData[] = "\x10\x00\x00\x00" // Length
+                                "\x05\x00"         // Version
+                                "\x08"             // Address size
+                                "\x00"             // Segment selector size
+                                "\x01\x00\x00\x00" // Offset entry count
+                                "\x04\x00\x00\x00" // offset[0]
+                                "\x04"             // DW_RLE_offset_pair
+                                "\x01"             // ULEB128 starting offset
+                                "\x02"             // ULEB128 ending offset
+                                "\x00";            // DW_RLE_end_of_list
+  DWARFDataExtractor Extractor(StringRef(SecData, sizeof(SecData) - 1),
+                               /*isLittleEndian=*/true,
+                               /*AddrSize=*/4);
+  DWARFListTableHeader Header(/*SectionName=*/".debug_rnglists",
+                              /*ListTypeString=*/"range");
+  uint64_t Offset = 0;
+  EXPECT_FALSE(!!Header.extract(Extractor, &Offset));
+  Optional<uint64_t> Offset0 = Header.getOffsetEntry(Extractor, 0);
+  EXPECT_TRUE(!!Offset0);
+  EXPECT_EQ(*Offset0, uint64_t(4));
+  Optional<uint64_t> Offset1 = Header.getOffsetEntry(Extractor, 1);
+  EXPECT_FALSE(!!Offset1);
+  EXPECT_EQ(Header.length(), sizeof(SecData) - 1);
+}
+
 } // end anonymous namespace