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    <p>Don't listen to the "C is old and that's why it doesn't have GC" folks. There are fundamental problems with GC that cannot be overcome which make it incompatible with C.</p> <p>The biggest problem is that accurate garbage collection requires the ability to scan memory and identify any pointers encountered. Some higher level languages limit integers not to use all the bits available, so that high bits can be used to distinguish object references from integers. Such languages may then store strings (which could contain arbitrary octet sequences) in a special string zone where they can't be confused with pointers, and all is well. A C implementation, however, cannot do this because bytes, larger integers, pointers, and everything else can be stored together in structures, unions, or as part of chunks returned by <code>malloc</code>.</p> <p>What if you throw away the accuracy requirement and decide you're okay with a few objects never getting freed because some non-pointer data in the program has the same bit pattern as these objects' addresses? Now suppose your program receives data from the outside world (network/files/etc.). I claim I can make your program leak an arbitrary amount of memory, and eventually run out of memory, as long as I can guess enough pointers and emulate them in the strings I feed your program. This gets a lot easier if you apply <a href="http://en.wikipedia.org/wiki/De_Bruijn_sequence" rel="noreferrer">De Bruijn Sequences</a>.</p> <p>Aside from that, garbage collection is just plain slow. You can find hundreds of academics who like to claim otherwise, but that won't change the reality. The performance issues of GC can be broken down into 3 main categories:</p> <ul> <li>Unpredictability</li> <li>Cache pollution</li> <li>Time spent walking all memory</li> </ul> <p>The people who will claim GC is fast these days are simply comparing it to the wrong thing: poorly written C and C++ programs which allocate and free thousands or millions of objects per second. Yes, these will also be slow, but at least predictably slow in a way you can measure and fix if necessary. A well-written C program will spend so little time in <code>malloc</code>/<code>free</code> that the overhead is not even measurable.</p>
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    1. POWas there a specific reason garbage collection was not designed for C?
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    1. POWas there a specific reason garbage collection was not designed for C?
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    1. COScan memory? Don't you just count references like java does?
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    2. COReference counting and garbage collection are not the same thing. Reference counting is clean and elegant, but cannot automatically free circular linked lists and other circularly-referenced objects, and it's very difficult to make it efficient in a multithreaded environment where different threads could be trying to increment or decrement the reference count at the same time.
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    3. CO-1 I can think of at least two garbage collectors for C off the top of my head. So "there are fundamental problems with GC that cannot be overcome which make it incompatible with C" is a false statement.
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