[DebugInfo] Correct out-of-bounds error message for DW_FORM_line_strp

[benmxwl-arm]

Summary

DW_FORM_line_strp reads from the .debug_line_str section, but
previously the out-of-bounds error reported the .debug_line section.

This incorrect error message showed up when debugging an issue with
some invalid DWARF5 data.

The verify_string.s test has now been extended to check this (which
required a small change to the DWARF verifier to also look at
DW_FORM_line_strp).

[jhenderson]

Looks reasonable to me, but please give it a few days for others to have a chance to review.

It may well be, but please make sure this is clang-formatted prior to submission. The pre-merge check is complaining about something to do with clang-format, but it might not be an issue with your change.

[benmxwl-arm]

I'm a little confused about the clang-format issue, it is complaining about a file I touched, though my commit was formatted locally (possibly some recent formatting change?) I'll double check that today.

[benmxwl-arm]

I'll submit this soon if there's no further comments.

I did look into the clang-format issues, but I can't reproduce it (git clang-format does not report any issue locally, there are a few places that need formatting but they are not lines I changed).

[probinson]

LGTM

llvm/lib/DebugInfo/DWARF/DWARFFormValue.cpp

if (Form == DW_FORM_GNU_str_index || Form == DW_FORM_strx ||
     Expected<uint64_t> StrOffset = U->getStringOffsetSectionItem(Offset);
     Index = Offset;
     if (!StrOffset)
       return StrOffset.takeError();
     Offset = *StrOffset;
   }
   // Prefer the Unit's string extractor, because for .dwo it will point to
   // .debug_str.dwo, while the Context's extractor always uses .debug_str.
-  DataExtractor StrData = Form == DW_FORM_line_strp
-                              ? C->getLineStringExtractor()
-                          : U ? U->getStringExtractor()
-                              : C->getStringExtractor();
+  bool IsDebugLineString = Form == DW_FORM_line_strp;
+  DataExtractor StrData =
+      IsDebugLineString ? C->getLineStringExtractor()
+                        : U ? U->getStringExtractor() : C->getStringExtractor();
   if (const char *Str = StrData.getCStr(&Offset))
     return Str;
   std::string Msg = FormEncodingString(Form).str();
   if (Index)
     Msg += (" uses index " + Twine(*Index) + ", but the referenced string").str();
-  Msg += (" offset " + Twine(Offset) + " is beyond .debug_str bounds").str();
+  Msg += (" offset " + Twine(Offset) + " is beyond " +
+          (IsDebugLineString ? ".debug_line_str" : ".debug_str") + " bounds")
+             .str();
   return make_error<StringError>(Msg,
       inconvertibleErrorCode());
 }
 
 std::optional<uint64_t> DWARFFormValue::getAsAddress() const {
   if (auto SA = getAsSectionedAddress())
     return SA->Address;
   return std::nullopt;

llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp

case DW_FORM_ref_addr: {
     }
     break;
   }
   case DW_FORM_strp:
   case DW_FORM_strx:
   case DW_FORM_strx1:
   case DW_FORM_strx2:
   case DW_FORM_strx3:
-  case DW_FORM_strx4: {
+  case DW_FORM_strx4:
+  case DW_FORM_line_strp: {
     if (Error E = AttrValue.Value.getAsCString().takeError()) {
       ++NumErrors;
       error() << toString(std::move(E)) << ":\n";
       dump(Die) << '\n';
     }
     break;
   }
   default:

llvm/test/tools/llvm-dwarfdump/X86/verify_strings.s

 # RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t.o
 # RUN: not llvm-dwarfdump -verify %t.o | FileCheck --check-prefix=VERIFY %s
 
 # Check that the verifier correctly diagnoses various error conditions with
-# the usage of string indices and string offsets tables.
+# the usage of string indices/offsets and string offsets tables.
+
+        .section .debug_line_str,"MS",@progbits,1
+str_comp_dir:
+        .asciz "llvm/test/tools/llvm-dwarfdump/X86"
 
         .section .debug_str,"MS",@progbits,1
 str_producer:
         .asciz "Handmade DWARF producer"
 
         .section .debug_str_offsets,"",@progbits
 # The string offsets table
         .long .debug_str_offsets_segment0_end-.debug_str_offsets_base0+4
         .short 5    # DWARF version
         .short 0    # Padding
 .debug_str_offsets_base0:
         .long str_producer
         .long 1000  # Invalid string address.
 .debug_str_offsets_segment0_end:
 
 # A simple abbrev section with a basic compile unit DIE.
         .section .debug_abbrev,"",@progbits
         .byte 0x01  # Abbrev code
         .byte 0x11  # DW_TAG_compile_unit
         .byte 0x00  # DW_CHILDREN_no
         .byte 0x25  # DW_AT_producer
         .byte 0x1a  # DW_FORM_strx
+        .byte 0x1b  # DW_AT_comp_dir
+        .byte 0x1f  # DW_FORM_line_strp
         .byte 0x72  # DW_AT_str_offsets_base
         .byte 0x17  # DW_FORM_sec_offset
         .byte 0x00  # EOM(1)
         .byte 0x00  # EOM(2)
 
         .section .debug_info,"",@progbits
 
 # The first unit's CU DIE has an invalid DW_AT_str_offsets_base which
 # renders any string index unresolvable.
 
 # DWARF v5 CU header.
         .long  CU1_5_end-CU1_5_version  # Length of Unit
 CU1_5_version:
         .short 5               # DWARF version number
         .byte 1                # DWARF Unit Type
         .byte 8                # Address Size (in bytes)
         .long .debug_abbrev    # Offset Into Abbrev. Section
 # The compile-unit DIE, which has DW_AT_producer and DW_AT_str_offsets.
         .byte 1                # Abbreviation code
         .byte 0                # Index of string for DW_AT_producer.
+        .long str_comp_dir     # Offset of debug line string for DW_AT_comp_dir
         .long 1000             # Bad value for DW_AT_str_offsets_base
         .byte 0 # NULL
 CU1_5_end:
 
 # The second unit's CU DIE uses an invalid string index.
 
 # DWARF v5 CU header
         .long  CU2_5_end-CU2_5_version  # Length of Unit
 CU2_5_version:
         .short 5               # DWARF version number
         .byte 1                # DWARF Unit Type
         .byte 8                # Address Size (in bytes)
         .long .debug_abbrev    # Offset Into Abbrev. Section
 # The compile-unit DIE, which has DW_AT_producer and DW_AT_str_offsets.
         .byte 1                # Abbreviation code
         .byte 100              # Invalid string index
+        .long str_comp_dir     # Offset of debug line string for DW_AT_comp_dir
         .long .debug_str_offsets_base0
         .byte 0 # NULL
 CU2_5_end:
 
-# The third unit's CU DIE uses a valid string index but the entry in the 
-# string offsets table is invalid. 
+# The third unit's CU DIE uses a valid string index but the entry in the
+# string offsets table is invalid.
 
 # DWARF v5 CU header
         .long  CU3_5_end-CU3_5_version  # Length of Unit
 CU3_5_version:
         .short 5               # DWARF version number
         .byte 1                # DWARF Unit Type
         .byte 8                # Address Size (in bytes)
         .long .debug_abbrev    # Offset Into Abbrev. Section
 # The compile-unit DIE, which has DW_AT_producer and DW_AT_str_offsets.
         .byte 1                # Abbreviation code
         .byte 1                # Index of string for DW_AT_producer.
+        .long str_comp_dir     # Offset of debug line string for DW_AT_comp_dir
         .long .debug_str_offsets_base0
         .byte 0 # NULL
 CU3_5_end:
-        
+# The fourth unit's CU DIE has an invalid offset for the debug line string.
+
+# DWARF v5 CU header
+        .long  CU4_5_end-CU4_5_version  # Length of Unit
+CU4_5_version:
+        .short 5               # DWARF version number
+        .byte 1                # DWARF Unit Type
+        .byte 8                # Address Size (in bytes)
+        .long .debug_abbrev    # Offset Into Abbrev. Section
+# The compile-unit DIE, which has DW_AT_producer and DW_AT_str_offsets.
+        .byte 1                # Abbreviation code
+        .byte 0                # Index of string for DW_AT_producer.
+        .long 99999            # Invalid offset of debug line string for DW_AT_comp_dir
+        .long .debug_str_offsets_base0
+        .byte 0 # NULL
+CU4_5_end:
+
 # VERIFY-DAG:      error: DW_FORM_strx used without a valid string offsets table:
 # VERIFY-DAG:      error: DW_FORM_strx uses index 100, which is too large:
-# VERIFY-DAG:      error: DW_FORM_strx uses index 1, but the referenced string offset 
+# VERIFY-DAG:      error: DW_FORM_strx uses index 1, but the referenced string offset
 # VERIFY-DAG-SAME: is beyond .debug_str bounds:
+# VERIFY-DAG:      error: DW_FORM_line_strp offset 99999 is beyond .debug_line_str bounds