4 ms·

unique_ptr has zero overhead

• cjfd 5y ago
  This appears to be incorrect. I have seen a cppcon talk about that. I think it may have been this one: https://www.youtube.com/watch?v=rHIkrotSwcc https://www.youtube.com/watch?v=rHIkrotSwcc . On the other hand, it is a very, very tiny minority of programmers who have to care about an overhead as low as this. Most of us should not waste one microsecond of our thinking time on this.
• JonChesterfield 5y ago
  Kind of true for unique_ptr as a C++ construct. Sadly if the platform ABI is not ignored there is (usually? might be free on some platforms) overhead relative to a void* when passing one between functions. Also there's the usual code size / compile time hazards of templates.
• berkut 5y ago
  Not when stepping through code in gdb/lldb in my experience in debug builds: they very often end up stepping in to the -> operator implementation for functions, which then requires me to step in again to get to the actual function call I wanted.
  • ncmncm 5y ago
    Measuring overhead of debug builds is a rookie mistake.
    • berkut 5y ago
      I'm not talking about code performance, I'm talking about human time of having to step through extra things while using a debugger to work out what's going on.
      • ncmncm 5y ago
        OK. I rely on "fin" a fair bit, at such times.
• ncmncm 5y ago
  unique_ptr has zero overhead except when passing or returning by move. But I don't find myself doing that anywhere performance matters. The overhead is not inherent, but is rather a consequence of C ABI choices inherited into C++ calling conventions. It is, though, real, and not easily fixed. E.g., RISC-V's ABI binding peobably suffers from the same overhead, not for any good reason, but just because the RISC-V crowd couldn't spare the attention to fix it.