[DWARF v5] Don't report an error when the .debug_rnglists section is empty or non-existent (PR 38297)

[wolfgangp]

Summary

When we are parsing a CU DIE we do attempt to find a valid range lists table header (the ranges are extracted on-demand). We fail to ignore a non-existent or empty .debug_rnglists section and report an error.

This doesn't address the larger question whether we should exit from llvm-dwarfdump with a non-zero code whenever an error is reported, whether verification is requested or not.

https://bugs.llvm.org/show_bug.cgi?id=38297

[JDevlieghere]

LGTM.

lib/DebugInfo/DWARF/DWARFUnit.cpp

if (!HasCUDie) {
     // DWARF v5 uses the .debug_rnglists and .debug_rnglists.dwo sections to
     // describe address ranges.
     if (getVersion() >= 5) {
       if (isDWO)
         setRangesSection(&Context.getDWARFObj().getRnglistsDWOSection(), 0);
       else
         setRangesSection(&Context.getDWARFObj().getRnglistsSection(),
                          toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0));
+      if (RangeSection->Data.size()) {
         // Parse the range list table header. Individual range lists are
         // extracted lazily.
         DWARFDataExtractor RangesDA(Context.getDWARFObj(), *RangeSection,
                                     isLittleEndian, 0);
         if (auto TableOrError =
                 parseRngListTableHeader(RangesDA, RangeSectionBase))
           RngListTable = TableOrError.get();
         else
           WithColor::error() << "parsing a range list table: "
                              << toString(TableOrError.takeError())
                              << '\n';
 
         // In a split dwarf unit, there is no DW_AT_rnglists_base attribute.
         // Adjust RangeSectionBase to point past the table header.
         if (isDWO && RngListTable)
           RangeSectionBase = RngListTable->getHeaderSize();
       }
+    }
 
     // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
     // skeleton CU DIE, so that DWARF users not aware of it are not broken.
   }
 
   return DieArray.size();
 }
 

test/DebugInfo/X86/dwarfdump-str-offsets.s

 # RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t.o
-# RUN: llvm-dwarfdump -v %t.o | FileCheck --check-prefix=COMMON --check-prefix=SPLIT %s
+# RUN: llvm-dwarfdump -v %t.o 2> %t.err | FileCheck --check-prefix=COMMON --check-prefix=SPLIT %s
+# 
+# Check that we don't report an error on a non-existent range list table.
+# RUN: FileCheck -allow-empty --check-prefix ERR %s < %t.err
 
 # Test object to verify dwarfdump handles v5 string offset tables.
 # We have 2 v5 CUs, a v5 TU, and a split v5 CU and TU.
 #
 
         .section .debug_str,"MS",@progbits,1
 str_producer:
         .asciz "Handmade DWARF producer"

 # 
 # SPLIT:       .debug_str_offsets.dwo contents:
 # SPLIT-NEXT:  0x00000000: Contribution size = 24, Format = DWARF32, Version = 5
 # SPLIT-NEXT:  0x00000008: 00000000 "Handmade split DWARF producer"
 # SPLIT-NEXT:  0x0000000c: 0000001e "V5_split_compile_unit"
 # SPLIT-NEXT:  0x00000010: 00000034 "/home/test/splitCU"
 # SPLIT-NEXT:  0x00000014: 00000047 "V5_split_type_unit"
 # SPLIT-NEXT:  0x00000018: 0000005a "V5_split_Mystruct"
+
+# ERR-NOT: parsing a range list table: