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[Object] object::ELFObjectFile::dynamic_symbol_begin(): skip symbol index 0

Authored by Higuoxing on Apr 4 2020, 3:17 AM.

Description

[Object] object::ELFObjectFile::dynamic_symbol_begin(): skip symbol index 0

Summary:
Note: This revision is very similar to D62296.

In D75756, we need getDynamicSymbolIterators() to skip first NULL symbol in .dynsym. And I believe it might be worth pointing this out in a separate patch to gather you experts' opinions.

I have checked that current code base will not be affected by this change.

dynamic_symbol_begin()
|- dynamic_symbol_end(): Ok
`- getDynamicSymbolIterators()
   |- addDynamicElfSymbols(): llvm/tools/llvm-objdump/llvm-objdump.cpp, Line 934
   |                          Ok, NULL symbol will be omitted by Line 945-947
   |                          StringRef Name = unwrapOrError(Symbol.getName(), Obj->getName());
   |                          if (Name.empty()) continue;
   |- dumpSymbolNameFromObject(): llvm/tools/llvm-nm/llvm-nm.cpp, Line 1192
   |                          There's no test for dumping dynamic debugging symbol. This patch helps improve llvm-nm behavior. (we should add test for this later)
   `- computeSymbolSizes(): llvm/lib/Object/SymbolSize.cpp, Line 52
      |- OProfileJITEventListener::notifyObjectLoaded(): llvm/lib/ExecutionEngine/OProfileJIT/OProfileJITEventListener.cpp, Line 92
      |                                                  Ok, NULL symbol will be omitted by Line 94-95
      |                                                  if (!Sym.getType() || *Sym.getType() != SF_Function) continue;
      |- IntelJITEventListener::notifyObjectLoaded(): llvm/lib/ExecutionEngine/IntelJITEvents/IntelJITEventListener.cpp, Line 98
      |                                               Ok, NULL symbol will be omitted by Line 124-126 (same as previous one)
      |- PerfJITEventListener::notifyObjectLoaded(): llvm/lib/ExecutionEngine/PerfJITEvents/PerfJITEventListener.cpp, Line 244
      |                                              Ok, NULL symbol will be omitted by Line 254-256, (same as previous one)
      |- SymbolizableObjectFile::create(): llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp, Line 73
      |                                    Ok, NULL symbol will be omitted by Line 75
      |                                    res->addSymbol()
      |                                    In addSymbol(), Line 167-168
      |                                    if (!Sec || (Obj && Obj->section_end() == *Sec)) return std::error_code();
      |- dumpCXXData(): llvm/tools/llvm-cxxdump/llvm-cxxdump.cpp, Line 189
      |                 Ok, NULL symbol will be omitted by Line 199-202
      |                 object::section_iterator SecI = *SecIOrErr;
      |                 // Skip external symbols.
      |                 if (SecI == Obj->section_end())
      |                   continue;
      `- printLineInfoForInput(): llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp, Line 418
                                  Ok, NULL symbol will be omitted by Line 430-477
                                  if (Type == object::SymbolRef::ST_Function) {
                                    ...
                                  }

Reviewers: grimar, jhenderson, MaskRay

Reviewed By: jhenderson, MaskRay

Subscribers: rupprecht, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76081

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