RFR: 8286331: jni_GetStringUTFChars() uses wrong heap allocator

[Thomas Stuefe]

On Fri, 6 May 2022 17:54:45 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> jni_GetStringUTFChars()  calls `AllocateHeap(length + 1, mtInternal, 0, AllocFailStrategy::RETURN_NULL);` to allocate memory, where it passes `0` as `NativeCallStack` reference, that results construction of `NativeCallStack`.
> 
> In `NativeCallStack`'s constructor, it performs stack walk to capture native call stack. This is unnecessary, if NMT detail tracking is not enabled.
> 
> It should use `char* AllocateHeap(size_t size,
>                    MEMFLAGS flags,
>                    AllocFailType alloc_failmode /* = AllocFailStrategy::EXIT_OOM*/)` heap allocator instead.

Change looks good.

So, we accidentally call `NativeCallStack(int toSkip);` ? If yes, and we don't like that, should we declare that constructor as explicit?

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Marked as reviewed by stuefe (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/8579