[BUG] Rust: libc::PTHREAD_MUTEX_INITIALIZER is incorrect

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Active
Tech stack
c, rust
Domain
embedded-iot, operating-systems

Research direction

Compare Rust libc's definition in src/unix/nuttx/mod.rs with NuttX's PTHREAD_MUTEX_INITIALIZER in include/pthread.h and NXSEM_NO_MHOLDER in include/nuttx/semaphore.h. Then inspect Rust std's use in library/std/src/sys/pal/unix/sync/mutex.rs. Done means an agreed approach produces a valid mutex initializer across the relevant NuttX configurations.

Written by the indexing model from the issue text.

Description

Arch: all Area: Applications Area: Posix OS: BSD OS: Linux OS: Mac OS: Windows Type: Bug
Description / Steps to reproduce the issue

Rust libc initializes PTHREAD_MUTEX_INITIALIZER to 0: https://github.com/rust-lang/libc/blob/c2744242b816317ea8b5c8e306eb829c080cb2b9/src/unix/nuttx/mod.rs#L310

But in NuttX this is generally not 0.
For example, defined here: https://github.com/apache/nuttx/blob/master/include/pthread.h#L359
Going into https://github.com/apache/nuttx/blob/master/include/pthread.h#L353
Which makes use of NXSEM_NO_MHOLDER, defined here: https://github.com/apache/nuttx/blob/master/include/nuttx/semaphore.h#L70
Furthermore, the initialization also depends on the configuration.

In Rust, std makes use of the constant to init mutexes, e.g. here: https://github.com/rust-lang/rust/blob/7d2cd0fbc092625ea371da704f15f80216d2220e/library/std/src/sys/pal/unix/sync/mutex.rs#L12

I'm not sure what the best solution is, I see some options:

  • remove the symbol definition from Rust (and update std to use pthread_mutex_init instead)
  • init the Rust definition to a matching value and either require a certain config or make sure the position of the non-zero values is independent from the config
  • update NuttX so the definition is always 0 (in addition to requiring a specific config)
On which OS does this issue occur?

[OS: Linux], [OS: BSD], [OS: Mac], [OS: Windows]

What is the version of your OS?

Irrelevant

NuttX Version

master

Issue Architecture

[Arch: all]

Issue Area

[Area: Posix], [Area: Applications]

Host information

No response

Verification
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