5 ms·

How big a performance hit? Double run time? Triple? 10x?

by richardwhiuk 9y ago

lisper 9y ago
I will take any performance hit over the potential for catastrophic failure by default.
- umanwizard 9y ago
  Then there is an easy solution: compile with -O0. What's the problem with optimizations being available for those who want them?
  - lisper 9y ago
    There is absolutely no problem with optimizations being available. The problem is that the standard gives the compiler license to muck with the semantics of the program in highly non-intuitive and potentially dangerous ways, and this is true regardless of what flags are passed to the compiler. So I can't depend on anything working even if I specify -O0, at least not by the standard. I am entirely at the mercy of the benevolence of my compiler vendor. If the compiler is going to be given license to make those kinds of dangerous non-intuitive changes to the program semantics I want that to be evident in the source code. For example, I would like to have to say something like YOU_MAY_ASSUME(NOTNULL(X)) before the compiler can assume that X is a pointer that can be dereferenced without signaling an error if it's null. That way the optimizations are still available, but it is easy to tell by looking at the source code if the author prioritized speed over safety and if there are potential gotchas hiding in the code as a result. The way it is now, the potential gotchas are like hidden land mines, nearly impossible to see, and ready to blow you to bits (pun intended :-) without warning.
    - jcranmer 9y ago
      > So I can't depend on anything working even if I specify -O0, at least not by the standard. I am entirely at the mercy of the benevolence of my compiler vendor. What you're basically saying is that you want semantics that's basically defined by the compiler vendor (or, more accurately, compiler/operating system/hardware trio), but you're pissed that the standard leaves it up to the compiler vendor as to whether or not you will get that option. You're already "at the mercy of the benevolence of [your] compiler vendor" to give you things like uint32_t, why is the presence of a -O0 inherently worse?
      - lisper 9y ago
        No, uint32_t has been part of the C standard library since C99.

How big a performance hit? Double run time? Triple? 10x?

lisper 9y ago

I will take any performance hit over the potential for catastrophic failure by default.

umanwizard 9y ago
Then there is an easy solution: compile with -O0. What's the problem with optimizations being available for those who want them?
- lisper 9y ago
  There is absolutely no problem with optimizations being available. The problem is that the standard gives the compiler license to muck with the semantics of the program in highly non-intuitive and potentially dangerous ways, and this is true regardless of what flags are passed to the compiler. So I can't depend on anything working even if I specify -O0, at least not by the standard. I am entirely at the mercy of the benevolence of my compiler vendor. If the compiler is going to be given license to make those kinds of dangerous non-intuitive changes to the program semantics I want that to be evident in the source code. For example, I would like to have to say something like YOU_MAY_ASSUME(NOTNULL(X)) before the compiler can assume that X is a pointer that can be dereferenced without signaling an error if it's null. That way the optimizations are still available, but it is easy to tell by looking at the source code if the author prioritized speed over safety and if there are potential gotchas hiding in the code as a result. The way it is now, the potential gotchas are like hidden land mines, nearly impossible to see, and ready to blow you to bits (pun intended :-) without warning.
  - jcranmer 9y ago
    > So I can't depend on anything working even if I specify -O0, at least not by the standard. I am entirely at the mercy of the benevolence of my compiler vendor. What you're basically saying is that you want semantics that's basically defined by the compiler vendor (or, more accurately, compiler/operating system/hardware trio), but you're pissed that the standard leaves it up to the compiler vendor as to whether or not you will get that option. You're already "at the mercy of the benevolence of [your] compiler vendor" to give you things like uint32_t, why is the presence of a -O0 inherently worse?
    - lisper 9y ago
      No, uint32_t has been part of the C standard library since C99.