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Minimal test - lines (45, 75)

Code

bool ProfilerCodeAddressService::GetFunction(const void* aPc,
                                             nsACString& aResult) {
  Entry& entry = GetEntry(aPc);

#if defined(XP_LINUX) || defined(XP_FREEBSD)
  // On Linux, most symbols will not be found by the MozDescribeCodeAddress call
  // that GetEntry does.  So we read the symbol table directly from the ELF
  // image.

  // SymbolTable currently assumes library offsets will not be larger than
  // 4 GiB.
  if (entry.mLOffset <= 0xFFFFFFFF && !entry.mFunction) {
    auto p = mSymbolTables.lookupForAdd(entry.mLibrary);
    if (!p) {
      if (!mSymbolTables.add(p, entry.mLibrary, SymbolTable())) {
        MOZ_CRASH("ProfilerCodeAddressService OOM");
      }
      profiler_get_symbol_table(entry.mLibrary, nullptr, &p->value());
    }
    entry.mFunction =
        SearchSymbolTable(p->value(), static_cast(entry.mLOffset));
  }
#endif

  if (!entry.mFunction || entry.mFunction[0] == '\0') {
    return false;
  }

  aResult = nsDependentCString(entry.mFunction);
  return true;
}

Minimal test - lines (15, 42)

Code

static char* SearchSymbolTable(SymbolTable& aTable, uint32_t aOffset) {
  size_t index;
  bool exact =
      BinarySearch(aTable.mAddrs, 0, aTable.mAddrs.Length(), aOffset, &index);

  if (index == 0 && !exact) {
    // Our offset is before the first symbol in the table; no result.
    return nullptr;
  }

  // Extract the (mangled) symbol name out of the string table.
  auto strings = reinterpret_cast(aTable.mBuffer.Elements());
  nsCString symbol;
  symbol.Append(strings + aTable.mIndex[index - 1],
                aTable.mIndex[index] - aTable.mIndex[index - 1]);

  // First try demangling as a Rust identifier.
  char demangled[1024];
  if (!profiler_demangle_rust(symbol.get(), demangled,
                              ArrayLength(demangled))) {
    // Then as a C++ identifier.
    DemangleSymbol(symbol.get(), demangled, ArrayLength(demangled));
  }
  demangled[ArrayLength(demangled) - 1] = '\0';

  // Use the mangled name if we didn't successfully demangle.
  return strdup(demangled[0] != '\0' ? demangled : symbol.get());
}