[llvm-readobj] - Change the error to warning when a section name is unknown.

[grimar]

Summary

We reported the error in this case.
But it was asked (https://reviews.llvm.org/D73193#inline-665595) to convert it
to a warning. This patch does it.

[jhenderson]

llvm/test/tools/llvm-readobj/ELF/invalid-shstrndx.test

16–34

Perhaps worth showing what is printed for this and subsequent section headers?

[MaskRay]

llvm/tools/llvm-readobj/ELFDumper.cpp

5755

if (Expected<StringRef> SecNameOrErr =
        Obj->getSectionName(&Sec, this->WarningHandler))
  Name = *SecNameOrErr;
else
  this->reportUniqueWarning(SecNameOrErr.takeError());

[MaskRay]

Allow a situation

It may be more accurate to say changing an error to a warning.

[grimar]

• Addressed review comments.

[jhenderson]

LGTM.

llvm/test/tools/llvm-readobj/ELF/invalid-shstrndx.test

 # RUN: yaml2obj %s -o %t
 # RUN: not llvm-readelf --headers -S 2>&1 %t | FileCheck %s -DFILE=%t --check-prefix=GNU
-# RUN: not llvm-readobj --headers -S 2>&1 %t | FileCheck %s -DFILE=%t --check-prefix=LLVM
+# RUN: llvm-readobj --headers -S 2>&1 %t | FileCheck %s -DFILE=%t --check-prefix=LLVM
 
 # GNU:      ELF Header:
 # GNU:        Section header string table index: 255
 # GNU-NEXT:   There are 3 section headers, starting at offset 0x58:
 # GNU:      Section Headers:
 # GNU-NEXT:  [Nr] Name
 # GNU-NEXT:  error: '[[FILE]]': section header string table index 255 does not exist
 
 # LLVM:      ElfHeader {
 # LLVM:        StringTableSectionIndex: 255
 # LLVM-NEXT: }
 # LLVM-NEXT: Sections [
-# LLVM-NEXT: error: '[[FILE]]': section header string table index 255 does not exist
+# LLVM-NEXT: warning: '[[FILE]]': section header string table index 255 does not exist
+# LLVM-NEXT: Section {
+# LLVM-NEXT:   Index: 0
+# LLVM-NEXT:   Name: <?> (0)
+# LLVM-NEXT:   Type: SHT_NULL (0x0)
+# LLVM-NEXT:   Flags [ (0x0)
+# LLVM-NEXT:   ]
+# LLVM-NEXT:   Address: 0x0
+# LLVM-NEXT:   Offset: 0x0
+# LLVM-NEXT:   Size: 0
+# LLVM-NEXT:   Link: 0
+# LLVM-NEXT:   Info: 0
+# LLVM-NEXT:   AddressAlignment: 0
+# LLVM-NEXT:   EntrySize: 0
+# LLVM-NEXT: }
+# LLVM:      Index: 1
+# LLVM-NEXT: Name: <?> (11)
+# LLVM:      Index: 2
+# LLVM-NEXT: Name: <?> (1)
 
 --- !ELF
 FileHeader:
   Class:     ELFCLASS64
   Data:      ELFDATA2LSB
   Type:      ET_REL
   Machine:   EM_X86_64
   SHStrNdx:  0xFF

llvm/test/tools/llvm-readobj/ELF/sections-no-section-header-string-table.test

 ## Check what --sections prints when there is no section header string table.
 
 # RUN: yaml2obj %s -o %t
 # RUN: llvm-readelf --sections %t \
 # RUN:   | FileCheck %s --strict-whitespace --match-full-lines --check-prefix=GNU
-# RUN: not llvm-readobj --sections %t 2>&1 \
+# RUN: llvm-readobj --sections %t 2>&1 \
 # RUN:   | FileCheck %s -DFILE=%t --check-prefix=LLVM
 
 #      GNU:Section Headers:
 # GNU-NEXT:  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
 # GNU-NEXT:  [ 0] <no-strings>      NULL            0000000000000000 000000 000000 00      0   0  0
 # GNU-NEXT:  [ 1] <no-strings>      PROGBITS        0000000000000000 000040 000000 00      0   0  0
 # GNU-NEXT:  [ 2] <no-strings>      PROGBITS        0000000000000000 000040 000000 00      0   0  0
 # GNU-NEXT:  [ 3] <no-strings>      STRTAB          0000000000000000 000040 000001 00      0   0  1

 # LLVM-NEXT:     Address: 0x0
 # LLVM-NEXT:     Offset: 0x40
 # LLVM-NEXT:     Size: 0
 # LLVM-NEXT:     Link: 0
 # LLVM-NEXT:     Info: 0
 # LLVM-NEXT:     AddressAlignment: 0
 # LLVM-NEXT:     EntrySize: 0
 # LLVM-NEXT:   }
-# LLVM-NEXT: error: '[[FILE]]': a section [index 2] has an invalid sh_name (0x1) offset which goes past the end of the section name string table
+# LLVM-NEXT: warning: '[[FILE]]': a section [index 2] has an invalid sh_name (0x1) offset which goes past the end of the section name string table
+# LLVM-NEXT:  Section {
+# LLVM-NEXT:    Index: 2
+# LLVM-NEXT:    Name: <?> (1)
+# LLVM-NEXT:    Type: SHT_PROGBITS (0x1)
+# LLVM-NEXT:    Flags [ (0x0)
+# LLVM-NEXT:    ]
+# LLVM-NEXT:    Address: 0x0
+# LLVM-NEXT:    Offset: 0x40
+# LLVM-NEXT:    Size: 0
+# LLVM-NEXT:    Link: 0
+# LLVM-NEXT:    Info: 0
+# LLVM-NEXT:    AddressAlignment: 0
+# LLVM-NEXT:    EntrySize: 0
+# LLVM-NEXT:  }
+# LLVM-NEXT: warning: '[[FILE]]': a section [index 3] has an invalid sh_name (0x15) offset which goes past the end of the section name string table
+# LLVM-NEXT:   Section {
+# LLVM-NEXT:     Index: 3
+# LLVM-NEXT:     Name: <?> (21)
+# LLVM-NEXT:     Type: SHT_STRTAB (0x3)
+# LLVM-NEXT:     Flags [ (0x0)
+# LLVM-NEXT:     ]
+# LLVM-NEXT:     Address: 0x0
+# LLVM-NEXT:     Offset: 0x40
+# LLVM-NEXT:     Size: 1
+# LLVM-NEXT:     Link: 0
+# LLVM-NEXT:     Info: 0
+# LLVM-NEXT:     AddressAlignment: 1
+# LLVM-NEXT:     EntrySize: 0
+# LLVM-NEXT:   }
+# LLVM-NEXT: warning: '[[FILE]]': a section [index 4] has an invalid sh_name (0xb) offset which goes past the end of the section name string table
+# LLVM-NEXT:   Section {
+# LLVM-NEXT:     Index: 4
+# LLVM-NEXT:     Name: <?> (11)
+# LLVM-NEXT:     Type: SHT_STRTAB (0x3)
+# LLVM-NEXT:     Flags [ (0x0)
+# LLVM-NEXT:     ]
+# LLVM-NEXT:     Address: 0x0
+# LLVM-NEXT:     Offset: 0x41
+# LLVM-NEXT:     Size: 29
+# LLVM-NEXT:     Link: 0
+# LLVM-NEXT:     Info: 0
+# LLVM-NEXT:     AddressAlignment: 1
+# LLVM-NEXT:     EntrySize: 0
+# LLVM-NEXT:   }
+# LLVM-NEXT: ]
 
 --- !ELF
 FileHeader:
   Class:    ELFCLASS64
   Data:     ELFDATA2LSB
   Type:     ET_DYN
   Machine:  EM_X86_64
   SHStrNdx: 0
 Sections:
   - Name:   .foo
     Type:   SHT_PROGBITS
     ShName: 0
   - Name:   .bar
     Type:   SHT_PROGBITS
     ShName: 1

llvm/tools/llvm-readobj/ELFDumper.cpp

 }
 
 template <class ELFT>
 void LLVMStyle<ELFT>::printSectionHeaders(const ELFO *Obj) {
   ListScope SectionsD(W, "Sections");
 
   int SectionIndex = -1;
   ArrayRef<Elf_Shdr> Sections = unwrapOrError(this->FileName, Obj->sections());
-  const ELFObjectFile<ELFT> *ElfObj = this->dumper()->getElfObject();
   std::vector<EnumEntry<unsigned>> FlagsList =
       getSectionFlagsForTarget(Obj->getHeader()->e_machine);
   for (const Elf_Shdr &Sec : Sections) {
-    StringRef Name = unwrapOrError(
-        ElfObj->getFileName(), Obj->getSectionName(&Sec, this->WarningHandler));
+    StringRef Name = "<?>";
+    if (Expected<StringRef> SecNameOrErr =
+            Obj->getSectionName(&Sec, this->WarningHandler))
+      Name = *SecNameOrErr;
+    else
+      this->reportUniqueWarning(SecNameOrErr.takeError());
+
     DictScope SectionD(W, "Section");
     W.printNumber("Index", ++SectionIndex);
     W.printNumber("Name", Name, Sec.sh_name);
     W.printHex(
         "Type",
         object::getELFSectionTypeName(Obj->getHeader()->e_machine, Sec.sh_type),
         Sec.sh_type);
     W.printFlags("Flags", Sec.sh_flags, makeArrayRef(FlagsList));