alloc | Professional Services Automation solution | Business library

Maybe I'm wrong, but it seems that last part:

The original code can be re-written in the following way:

Unfortunately (?), the easiest way to know for sure what those categories map to is to look at OpenJDK source code. The NMT tag you are looking for is mtServiceability. This would show that "serviceability" are basically diagnostic interfaces in JDK/JVM: JVMTI, heap dumps, etc.

But the same kind of thing is clear from observing that stack trace sample you are showing mentions ThreadStackTrace::dump_stack_at_safepoint -- that is something that dumps the thread information, for example for jstack, heap dump, etc. If you have a suspicion for the memory leak in that code, you might try to build a MCVE demonstrating it, and submitting the bug against OpenJDK, or showing it to a fellow OpenJDK developer. You probably know better what your application is doing to cause thread dumps, focus there.

That being said, I don't see any obvious memory leaks in StackFrameInfo, neither can I reproduce any leak with stress tests, so maybe what you are seeing is "just" thread dumping over the larger and larger thread stacks. Or you capture it when thread dump is happening. Or... It is hard to say without the MCVE.

Update: After playing with MCVE, I realized that it reproduces with 17.0.1, but not with either mainline development JDK, or JDK 18 EA, or JDK 17.0.2 EA. I tested with 17.0.2 EA before, so was not seeing it, dang. Bisection between 17.0.1 and 17.0.2 EA shows it was fixed with JDK-8273902 backport. 17.0.2 releases this week, so the bug should disappear after you upgrade.

C++20 supports allocation during constexpr time, as long as the allocation is completely deallocated by the time constant evaluation ends. So, for instance, this very silly example is valid in C++20:

Laziness to the rescue. We can recursively define a list of all the sub-automata, such that their transitions index into that same list:

The real reason is in V8 memory optimization. When you store integers - it stores the 32 bit number in place, But when you store double-number - it is stored differently (as an object) - so yValues array contains the reference but the actual value stored in heap. So in your example you just used all heap memory. To see the limit, use: console.memory and you'll see something like this:

The ambiguity is that std::string and std::string_view are both constructible from const char *. That makes things like

Your program is actually ill-formed, though the error may be hard to understand. constexpr allocation support in C++20 is limited - you can only have transient allocation. That is, the allocation has to be completely deallocated by the end of constant evaluation.

So you cannot write this:

Yes, alloca is functionally equivalent to a local variable length array, i.e. this: