[DWARFVerifier] Fix debug_str_offsets DWARF version detection

llvm/include/llvm/DebugInfo/DWARF/DWARFVerifier.h

@@ -361,7 +361,8 @@ class DWARFVerifier {
   /// \returns true if the .debug_line verifies successfully, false otherwise.
   bool handleDebugStrOffsets();
   bool verifyDebugStrOffsets(
-      StringRef SectionName, const DWARFSection &Section, StringRef StrData,
+      uint8_t MaxVersion, StringRef SectionName, const DWARFSection &Section,
+      StringRef StrData,
       void (DWARFObject::*)(function_ref<void(const DWARFSection &)>) const);
 
   /// Emits any aggregate information collected, depending on the dump options

llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp

@@ -1882,29 +1882,31 @@ bool DWARFVerifier::handleDebugStrOffsets() {
   const DWARFObject &DObj = DCtx.getDWARFObj();
   bool Success = true;
   Success &= verifyDebugStrOffsets(
-      ".debug_str_offsets.dwo", DObj.getStrOffsetsDWOSection(),
-      DObj.getStrDWOSection(), &DWARFObject::forEachInfoDWOSections);
+      DCtx.getMaxDWOVersion(), ".debug_str_offsets.dwo",
+      DObj.getStrOffsetsDWOSection(), DObj.getStrDWOSection(),
+      &DWARFObject::forEachInfoDWOSections);
   Success &= verifyDebugStrOffsets(
-      ".debug_str_offsets", DObj.getStrOffsetsSection(), DObj.getStrSection(),
-      &DWARFObject::forEachInfoSections);
+      DCtx.getMaxVersion(), ".debug_str_offsets", DObj.getStrOffsetsSection(),
+      DObj.getStrSection(), &DWARFObject::forEachInfoSections);
   return Success;
 }
 
 bool DWARFVerifier::verifyDebugStrOffsets(
-    StringRef SectionName, const DWARFSection &Section, StringRef StrData,
+    uint8_t MaxVersion, StringRef SectionName, const DWARFSection &Section,
+    StringRef StrData,
     void (DWARFObject::*VisitInfoSections)(
         function_ref<void(const DWARFSection &)>) const) {
   const DWARFObject &DObj = DCtx.getDWARFObj();
-  uint16_t InfoVersion = 0;
-  DwarfFormat InfoFormat = DwarfFormat::DWARF32;
+
+  std::optional<DwarfFormat> MaybeInfoFormat;
   (DObj.*VisitInfoSections)([&](const DWARFSection &S) {
-    if (InfoVersion)
+    if (MaybeInfoFormat)
       return;
     DWARFDataExtractor DebugInfoData(DObj, S, DCtx.isLittleEndian(), 0);
     uint64_t Offset = 0;
-    InfoFormat = DebugInfoData.getInitialLength(&Offset).second;
-    InfoVersion = DebugInfoData.getU16(&Offset);
+    MaybeInfoFormat = DebugInfoData.getInitialLength(&Offset).second;
   });
+  DwarfFormat InfoFormat = MaybeInfoFormat.value_or(DwarfFormat::DWARF32);
 
   DWARFDataExtractor DA(DObj, Section, DCtx.isLittleEndian(), 0);
 
@@ -1915,7 +1917,8 @@ bool DWARFVerifier::verifyDebugStrOffsets(
     DwarfFormat Format;
     uint64_t Length;
     uint64_t StartOffset = C.tell();
-    if (InfoVersion == 4) {
+    if (MaxVersion == 4) {
+      // Pre-standardization debug_str_offsets had no header.
       Format = InfoFormat;
       Length = DA.getData().size();
       NextUnit = C.tell() + Length;

llvm/test/tools/llvm-dwarfdump/X86/debug-str-offsets-mixed-dwarf-4-5.yaml

@@ -0,0 +1,57 @@
+# RUN: yaml2obj %s -o %t.o
+# RUN: llvm-dwarfdump -debug-str-offsets -verify %t.o | FileCheck %s
+
+# CHECK: Verifying .debug_str_offsets...
+# CHECK: No errors
+
+# Check that when mixing standard DWARF 4 debug information with standard DWARF
+# 5 debug information, the verifier correctly interprets the debug_str_offsets
+# section as a standards-conforming DWARF 5 section.
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+DWARF:
+  debug_str:
+    - 'cu1'
+    - 'cu2'
+  debug_str_offsets:
+    - Offsets:
+        - 0x0
+  debug_abbrev:
+    - Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+        - Code:            0x2
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strx1
+            - Attribute:       DW_AT_str_offsets_base
+              Form:            DW_FORM_sec_offset
+  debug_info:
+    - Version:         4
+      AbbrevTableID:   0
+      AbbrOffset:      0x0
+      AddrSize:        8
+      Entries:
+        - AbbrCode:        0x1
+          Values:
+            - Value:           0x4
+    - Version:         5
+      UnitType:        DW_UT_compile
+      AbbrOffset:      0x0
+      AddrSize:        8
+      AbbrevTableID:   0
+      Entries:
+        - AbbrCode:        0x2
+          Values:
+            - Value:           0x0
+            - Value:           0x8 # str offsets base