PVS-Studio warning V576 for javascriptcore

void CodeBlock::printStructure(
  const char* name, const Instruction* vPC, int operand) const
{
  unsigned instructionOffset = vPC - m_instructions.begin();
  printf("  [%4d] %s: %s\n", instructionOffset, name,
    pointerToSourceString(vPC[operand].u.structure).
      UTF8String().c_str());
}

This suspicious code was found in javascriptcore project by PVS-Studio static code analyzer.
Warning message is:
V576 Incorrect format. Consider checking the second actual argument of the 'printf' function. The SIGNED integer type argument is expected. codeblock.cpp 280

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