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> What's a "stop the world GC"? I joke, of course, but I really haven't seen anything like that in a long, long time. Actually, many modern GCs are still "stop

by Arelius 13y ago

> What's a "stop the world GC"? I joke, of course, but I really haven't seen anything like that in a long, long time. Actually, many modern GCs are still "stop the world" including many generational GCs. the alternative generally has overhead elsewhere that hurts performance. GC has a lot of tradeoffs. > A C++ program doesn't come with an inherent advantage in memory handling. Many of the same techniques (creating and managing pools of memory) can and are being done in applications (like Cassandra) on the JVM (off-heap memory). Sure, but it sure is a lot easier in C++ since the entire infrastructure doesn't assume GC is operating. I don't even know a way to reliably allocate a temporary object in Java that won't trigger GC I could guess some things that would probably cause the optimizer to allocate it on the stack, but that precludes having the temporary lifetime outlive the stack. (It must however be said, I'm not really a Java programmer) > Garbage collectors give you two things -- ... and (when you take pointers away) increased security. As you just said, increased security is from taking pointers away, which is completely orthogonal to GC.

rbehrends 13y ago
> As you just said, increased security is from taking pointers away, which is completely orthogonal to GC. That's not what he said. Removing pointer arithmetic [1] is part of getting memory safety, but not the entire story. Avoiding dangling references is another part of memory safety, and GC is one way to accomplish that; it's not orthogonal. [1] You cannot actually eliminate pointers entirely; you can disguise them, but if you want a dynamic heap and not just static memory, you need to be able to reference memory within the heap. When people talk about eliminating pointers, they generally mean unsafe C-style pointers.
- Arelius 13y ago
  > Avoiding dangling references is another part of memory safety, and GC is one way to accomplish that; it's not orthogonal. It's the removal of the `free` and `delete` semantics that avoid dangling references. Not GC. While GC posits a good alternative to many of these problems. GC doesn't actually help memory safety at all. Unless you consider memory leaks to be a matter of "memory safety".
  - rbehrends 13y ago
    Avoiding premature free()s is precisely what garbage collection accomplishes in this context, because you will never have to call free() to avoid running out of memory.

by Arelius 13y ago

rbehrends 13y ago

> As you just said, increased security is from taking pointers away, which is completely orthogonal to GC. That's not what he said. Removing pointer arithmetic [1] is part of getting memory safety, but not the entire story. Avoiding dangling references is another part of memory safety, and GC is one way to accomplish that; it's not orthogonal. [1] You cannot actually eliminate pointers entirely; you can disguise them, but if you want a dynamic heap and not just static memory, you need to be able to reference memory within the heap. When people talk about eliminating pointers, they generally mean unsafe C-style pointers.

Arelius 13y ago
> Avoiding dangling references is another part of memory safety, and GC is one way to accomplish that; it's not orthogonal. It's the removal of the `free` and `delete` semantics that avoid dangling references. Not GC. While GC posits a good alternative to many of these problems. GC doesn't actually help memory safety at all. Unless you consider memory leaks to be a matter of "memory safety".
- rbehrends 13y ago
  Avoiding premature free()s is precisely what garbage collection accomplishes in this context, because you will never have to call free() to avoid running out of memory.