'Compilation Provider' (Sony, Microsoft, Apple, Google. Support for architectures and tooling has decades to catch up. One of the important reasons why C++ got popular is that it had near full backwards compat. We have gazillion of lines/projects in C++. Plus, relying on GC means it's nearly impossible to handle the 'replace a C library' use case.Īndreas Bergmeier 6 February 2017 at 23:31 That's nice, though you're still buying into the fundamental tradeoffs of GC: some combination of increased memory usage, reduced throughput, and pauses. (Those checks are in the process of being expanded, though it's hard to say where D will end up.) Go can also do this, because its GC supports interior pointers. D has some special-casing for this case, though its existing safety checks are limited and easily circumvented accidentally or deliberately.

Update As I half-expected, people did turn up a couple of non-toy languages that can handle this example. This is my go-to example every time someone suggests that modern C++ is just as suitable for safe systems programming as Rust. (The C++ Core Guidelines lifetime checking proposal proposes such checks, but it's incomplete and hasn't received any updates for over a year.) Most other languages simply prevent you from giving away an interior reference, or require y to refer to a distinct heap object from the X. C/C++ can't do it because the compiler does not perform the lifetime checks.

It compiles down to what you'd expect a C compiler to produce (pointer addition) with no space or time overhead.Īs far as I know, no other remotely mainstream language can express this, for various reasons. Crucially, the Rust compiler will verify that all callers of the getter prevent the returned reference from outliving the X object. Then we define a getter method that returns the field by reference. This defines an aggregate type containing a field y of type Y directly (not as a separate heap object).

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