[PATCH] D155353: [llvm-readobj] Print <null> for relocation target with an empty name

[Fangrui Song via Phabricator via llvm-commits]

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For a relocation, we don't differentiate the two cases:

- the symbol index is 0
- the symbol index is non zero, the type is not STT_SECTION, and the name is empty. Clang generates such local symbols for RISC-V linker relaxation.

So we may print

      Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
  000000000000001c  0000000100000039 R_RISCV_32_PCREL       0000000000000000 0
  
  // llvm-readobj
  0x1C R_RISCV_32_PCREL - 0x0

while GNU readelf prints "<null>", which is clearer. Let's match the GNU behavior.
Related to https://reviews.llvm.org/D81842

  000000000000001c  0000000100000039 R_RISCV_32_PCREL       0000000000000000 <null> + 0
  
  // llvm-readobj
  0x1C R_RISCV_32_PCREL <null> 0x0


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D155353

Files:
  lld/test/ELF/mips-eh_frame-pic.s
  llvm/test/CodeGen/RISCV/fixups-diff.ll
  llvm/test/DebugInfo/RISCV/dwarf-riscv-relocs.ll
  llvm/test/DebugInfo/RISCV/relax-debug-frame.ll
  llvm/test/MC/ELF/RISCV/gen-dwarf.s
  llvm/test/MC/RISCV/cfi-advance.s
  llvm/test/MC/RISCV/fde-reloc.s
  llvm/test/MC/RISCV/scoped-relaxation.s
  llvm/test/tools/llvm-readobj/ELF/reloc-zero-name-or-value.test
  llvm/test/tools/yaml2obj/ELF/symbol-name.yaml
  llvm/tools/llvm-readobj/ELFDumper.cpp

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