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The blog post you referenced in [1] doesn't mention managed language runtimes itself, so let me make sure I understand the point. If I understand your point cor

The blog post you referenced in [1] doesn't mention managed language runtimes itself, so let me make sure I understand the point. If I understand your point correctly, it's that with managed language runtimes, particularly mature ones like HotSpot and V8, the C heap isn't used in the typical C way; instead, the runtime has its own heap, closely integrated with the garbage collector. In that case, Go probably has the same problem, just because it tries not to use libc at all. I'm guessing that CPython isn't as bad, because it doesn't use a garbage collector. No idea about Ruby.

bcantrill 11y ago
Yes -- and you understand the point correctly. And it's independent of whether a language is GC'd or not; to provide memory safety means to provide a layer of indirection between the system's notion of memory and that of the run-time -- and that layer becomes opaque to traditional native tools. I apologize that that reference was a little hasty; [1] is a much, much better one. [1] https://queue.acm.org/detail.cfm?id=2039361 https://queue.acm.org/detail.cfm?id=2039361
- pcwalton 11y ago
  > And it's independent of whether a language is GC'd or not; to provide memory safety means to provide a layer of indirection between the system's notion of memory and that of the run-time -- and that layer becomes opaque to traditional native tools. No! You can enforce memory safety at compile time and use the platform's native memory allocation subsystem. There's no need for memory safety to imply any extra runtime support.
  - mwcampbell 11y ago
    As far as I can tell you're right in principle, but even Rust doesn't currently deliver that in practice. With Rust 1.0, at least on Linux, Rust uses its own bundled jemalloc rather than the libc malloc. So IIUC, that means that you can't take advantage of things like libumem, the alternative malloc described in the blog post bcantrill referenced a few comments ago.
    - pcwalton 11y ago
      Yeah, I figured someone would bring up jemalloc. :) As of a few days ago, Rust allocation is pluggable [1]. jemalloc is considered a "feature" in the Cargo sense which can be turned on and off. (The immediate impetus for this feature work was to use HeapAlloc() on Windows.) [1]: https://github.com/rust-lang/rust/blob/master/src/liballoc/heap.rs https://github.com/rust-lang/rust/blob/master/src/liballoc/h...

bcantrill 11y ago

Yes -- and you understand the point correctly. And it's independent of whether a language is GC'd or not; to provide memory safety means to provide a layer of indirection between the system's notion of memory and that of the run-time -- and that layer becomes opaque to traditional native tools. I apologize that that reference was a little hasty; [1] is a much, much better one. [1] https://queue.acm.org/detail.cfm?id=2039361 https://queue.acm.org/detail.cfm?id=2039361

pcwalton 11y ago
> And it's independent of whether a language is GC'd or not; to provide memory safety means to provide a layer of indirection between the system's notion of memory and that of the run-time -- and that layer becomes opaque to traditional native tools. No! You can enforce memory safety at compile time and use the platform's native memory allocation subsystem. There's no need for memory safety to imply any extra runtime support.
- mwcampbell 11y ago
  As far as I can tell you're right in principle, but even Rust doesn't currently deliver that in practice. With Rust 1.0, at least on Linux, Rust uses its own bundled jemalloc rather than the libc malloc. So IIUC, that means that you can't take advantage of things like libumem, the alternative malloc described in the blog post bcantrill referenced a few comments ago.
  - pcwalton 11y ago
    Yeah, I figured someone would bring up jemalloc. :) As of a few days ago, Rust allocation is pluggable [1]. jemalloc is considered a "feature" in the Cargo sense which can be turned on and off. (The immediate impetus for this feature work was to use HeapAlloc() on Windows.) [1]: https://github.com/rust-lang/rust/blob/master/src/liballoc/heap.rs https://github.com/rust-lang/rust/blob/master/src/liballoc/h...