5 ms·

4) string concatenation

• piker 6y ago
  Probably (1) above, no?
  • pjmlp 6y ago
    NULL terminated strings are quite bad for performance, because you need to transverse them to find the terminator. Now try to concatenate a bunch of them in C.
    • harveywi 6y ago
      >you need to traverse them to find the terminator. Why not just do a binary search through the entire 256TB virtual memory space, finding the largest memory address that doesn't segfault? :-)
    • varajelle 6y ago
      C++ code usually use std:: string, std::string_view, or other string classes that stores the string size and has some capacity pre-allocated to avoid such issues.
      • pjmlp 6y ago
        The (1) also mentions C. I would partially agree with you, if it only mentioned C++. Only partially, because too many C++ devs still use plain old C strings.
      • zlynx 6y ago
        Profiling is essential. I found a performance bug in calling some C++ functions a while ago, because they accepted a const std::string& and were being called in loops with a C const char*. Every single call had to construct a std::string involving a strlen, allocation and copy. std::string_view is a nice fix for this but few programmers seem to use it yet.
    • astrobe_ 6y ago
      Like this ? const char* strings[]={"ab","cd", "ef", "gh", ....}; char result[1024*1024*1024*1024]; size_t sz=0; for(int i=0; i<sizeof(strings); i++) { size_t len=strlen(strings[i]); memcpy(result+sz, strings[i], len); sz+=len; } result[sz]=0;