Giving C a superpower: custom header file (safe_c.h)

Post by atherton94027 » Tue, Nov 18, 2025, 1:26 AM UTC

jesse__ wrote: post #197

jerf wrote: post #52

Earlier quoted context omitted.

Because about 99% of the time the garbage collect is a negligible portion of your runtime at the benefit of a huge dollop of safety. People really need to stop acting like a garbage collector is some sort of cosmic horror that automatically takes you back to 1980s performance or something. The cases where they are unsuitable are a minority, and a rather small one at that. If you happen to live in that minority, great…

> Because about 99% of the time the garbage collect is a negligible portion of your runtime lol .. reality disagrees with you. https://people.cs.umass.edu/~emery/pubs/gcvsmalloc.pdf#:~:te... On page 3 they broadly conclude that if you use FIVE TIMES as much memory as your program would if managed manually, you get a 9% performance hit. If you only use DOUBLE, you get as much as a 70% hit. Further on, there are compre…

Post by lmm » Tue, Nov 18, 2025, 1:33 AM UTC

spacedcowboy wrote: post #43

woodruffw wrote: post #36

Intentionally or not, this post demonstrates one of the things that makes safer abstractions in C less desirable: the shared pointer implementation uses a POSIX mutex, which means it’s (1) not cross platform, and (2) pays the mutex overhead even in provably single-threaded contexts. In other words, it’s not a zero-cost abstraction. C++’s shared pointer has the same problem; Rust avoids it by having two types (Rc and…

The number of times I might want to write something in C and have it less likely to crash absolutely dwarfs the number of times I care about that code being cross-platform. Sure, cross-platform is desirable, if there's no cost involved, and mandatory if you actually need it, but it's a "nice to have" most of the time, not a "needs this". As for mutex overheads, yep, that's annoying, but really, how annoying ? Modern…

Post by lmm » Tue, Nov 18, 2025, 1:38 AM UTC

lelanthran wrote: post #153

KerrAvon wrote: post #107

Earlier quoted context omitted.

Outside of hobbyist things, performance-critical code is the only responsible use case for a non-memory safe language like C in 2025, so of course it does. (Even that window is rapidly closing, though; languages like Rust and Swift can be better than C for perf-critical things because of the immutability guarantees.)

> Outside of hobbyist things, performance-critical code is the only responsible use case for a non-memory safe language like C in 2025, so of course it does. Maybe; I sometimes write non-hobbyist non-performance-critical code in C. I'm actually planning a new product for 2026 that might be done in C (the current iteration of that product line is in Go, the previous iteration was in Python). I've few qualms about writ…

Post by kazinator » Tue, Nov 18, 2025, 1:49 AM UTC

  // The Old Way (don't do this)
  char* include_pattern = NULL;
  if (optarg) {
      include_pattern = strdup(optarg);
  }
  // ...200 lines later...
  if (some_error) {
      if (include_pattern) free(include_pattern); // Did I free it? Did I??
      return 1;

  // ...200 lines later...
  // common return block

  out:
  free(include_pattern);  // free(NULL) allowed since before 1989 ANSI C
  return result;

Post by groundzeros2015 » Tue, Nov 18, 2025, 2:03 AM UTC

woodruffw wrote: post #51

kouteiheika wrote: post #46

Earlier quoted context omitted.

I think that's an orthogonal issue. It's not that C++'s shared pointer is not a zero cost abstraction (it's as much a zero cost abstraction as in Rust), but that it only provides one type of a shared pointer. But I suppose we're wasting time on useless nitpicking. So, fair enough.

I think they’re one and the same: C++ doesn’t have program-level thread safety by construction, so primitives like shared pointers need to be defensive by default instead of letting the user pick the right properties for their use case. Edit: in other words C++ could provide an equivalent of Rc, but we’d see no end of people complaining when they shoot themselves in the foot with it. (This is what “zero cost abstract…