nodejs12: static assert fails on PPC: thread_local_top_ = 100 instead of 24 * pointer size

[barracuda156]

Details

In nodejs12 size of ThreadLocalTop is defined as:

constexpr uint32_t kSizeInBytes = 24 * kSystemPointerSize;

Which for 32-bit system means 96. However when building for PPC, I get a bunch of static assert failures due to thread_local_top_ being = 100: nodejs/node#30323 (comment) (yes, I checked that, adding an extra assert on its size explicitly).

For w/e reason, in nodejs16 the same place was changed to:

#ifdef V8_ENABLE_CONSERVATIVE_STACK_SCANNING
  static constexpr uint32_t kSizeInBytes = 25 * kSystemPointerSize;
#else
  static constexpr uint32_t kSizeInBytes = 24 * kSystemPointerSize;
#endif

And then, in current version, it is 26 and 25: https://github.com/nodejs/node/blob/main/deps/v8/src/execution/thread-local-top.h

Should I just change 24 to 25, so that assertion succeeds? Or do I have a bug with how thread_local_top_ is calculated? If the latter is likely, any idea where to look?

P. S. The context of why nodejs12: I am trying to fix it for Macports for MacOS PPC, and there is a branch of nodejs12 supporting ppc32 on AIX/Linux, so it should be feasible and likely easier to make it work. If it does, then I could try a newer version.

Node.js version

12.22.12

Example code

No response

Operating system

MacOS 10.6.8 Server, GCC 12.2.0

Scope

Build

Module and version

Not applicable.

[barracuda156]

Log for the reference:
nodejs12ppc_fail.log

[github-actions]

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[barracuda156]

If anyone could help with some advice, it will be great. The issue is still relevant with the current version of NodeJS.

[RedYetiDev]

CC @nodejs/v8

[barracuda156]

CC @nodejs/v8

@RedYetiDev This could be macOS-specific in fact, I am not sure if size of these structures will be the same under ELF ABI.

[RedYetiDev]

Thanks! I'll add the label back.