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There's no law that states that you have to litter your code with calls to malloc()/free() when writing C. If reference counting won't do, there's more than one
by qwph 18y ago
There's no law that states that you have to litter your code with calls to malloc()/free() when writing C.
If reference counting won't do, there's more than one garbage collector freely available, and they're not all that hard to implement from first principles if the mood takes you.
- timr 18y agoOkay, so now you're writing your own memory management. How much work are you willing to do to avoid a language which gives you the feature for free?
- qwph 18y agoIt was an interesting exercise. (It gratified my intellectual curiosity, you might say...) How do you suppose memory management works in high-level languages? Magic?
- timr 18y agoNo. Everyone knows that there are little memory gnomes that run around your system, sweeping up bits.
- tptacek 18y agoThis is exactly what you really do get in garbage-collected programs.
- timr 18y agoDude...seriously: there are garbage collectors for C++. They're not exclusive to C! Moreover, the C++ garbage collectors are pretty darned easy to use, given that the language builds in support for custom allocators, overriding new/delete, etc.
- tptacek 18y agoThe fact that it is trivially simple to garbage collect both C and C++ code neutralizes the "automatic memory management" advantage, dubious as it was, from C++.
- timr 18y agoNot really. One reason that you infrequently see C++ programs using garbage collection, is because the language includes some nice tools that mitigate many of the pain points that drive people to use GC in the first place. If you're using C++ as its own language, you get many of the nice things that come with memory management in dynamic languages, but you don't have to pay for it at runtime (the inclusion of shared_ptr in C++0x is a great example of this, actually). If you merely use C++ as "C with classes" (I'm not saying that you do this...just generally), then you don't see this benefit of the language.
- tptacek 18y agoIt's weird that you think you don't pay for the C++ Standard Library's implementation of reference counting at runtime.
- timr 18y agoWhat are you talking about? auto_ptr? shared_ptr? You don't pay for these if you don't use them; the language gives you the option of trading safety for speed. That's what I meant when I said that you don't have to pay for the features. In any case, the reference-counting used by the safe pointers is probably an order of magnitude less heavy than a garbage collector. Even if you use them, you aren't paying that much...
- tptacek 18y agoYou don't think it's nitpicky to suggest that C++ gives you automatic memory "for free", as long as you don't ever use it? Garbage collection is not an "order of magnitude" more heavy than reference counting, and there's more than one axis to measure memory management on --- in fact, there are several axes for allocation transactions alone. Just as importantly, if you go to Google Code Search and randomly select ten C++ projects that (a) have more than 10,000 lines of ".cpp" and ".i" file code and (b) use shared_ptr, I'm betting you're going to find that 8 of them rewrote some of the memory allocator for performance reasons. All the fancy template BS in the world doesn't save you from the fact that "new" is just "malloc", and there's no one allocator design that works for every program.
- tptacek 18y agoI don't know, but when I want nice memory management in C code (and usually, if I'm writing something in C, it's at least partly because I care a lot about how memory is managed), I just use Boehm GC.
- timr 18y agoOkay, so you've introduce a third-party dependency. Again, how much work are you willing to do to duplicate a language feature that C++ gives you for free?
- tptacek 18y agoOh give me a break. Until the new standard hit, practically everything that made C++ bearable was a third-party dep on Boost. And the difference between Boost and Boehm GC is, I don't have to read documentation or even change my code to use Boehm. "Avoiding third party deps". The dev team that embraced that standard sure sounds like a blast to work on. The wheel I can't wait to reinvent? Zlib.
- kingkongrevenge 18y agoComparing a third party GC library to TR1 stuff supported by many compiler vendors and vetted by the committee is a bit of a stretch.
- tptacek 18y agoComparing the most famous garbage collection library of all time to the output of a standards body is not a stretch, and now we're into "some third party deps are good --- the ones that support my argument --- and some are bad --- the ones that support yours". I'm happy to consider us stalemated and move on.
- kingkongrevenge 18y ago> I'm happy to consider us stalemated Somehow I doubt it.
- DarkShikari 18y agoIf you're peppering your code with malloc/free, it has nothing to do with not "writing your own memory management"--your code is just badly designed to begin with.
- KirinDave 18y agoOne word: "Greenspun"