COMP: Use value initialization to zero-initialize thread id variable

[jhlegarreta]

Use value initialization to zero-initialize thread id variable.

Fixes:

In file included from
 Core/Common/src/itkPlatformMultiThreader.cxx:35:
[CTest: warning matched]
 Core/Common/src/itkPlatformMultiThreaderPosix.cxx:172:28:
 warning: zero as null pointer constant [-Wzero-as-null-pointer-constant]
  172 |   pthread_t threadHandle = 0;
      |                            ^
      |                            nullptr
[CTest: warning suppressed] 1 warning generated.

raised for example in:
https://open.cdash.org/viewBuildError.php?type=1&buildid=10477917

and

ITK/Modules/Core/Common/include/itkThreadSupport.h:45:55:
 warning: zero as null pointer constant [-Wzero-as-null-pointer-constant]
   45 | constexpr ThreadProcessIdType ITK_DEFAULT_THREAD_ID = 0;
      |                                                       ^
      |                                                       nullptr

reported by a local build.

PR Checklist

• No API changes were made (or the changes have been approved)
• No major design changes were made (or the changes have been approved)

[thewtex]

💯

[jhlegarreta]

Sorry, forgot to force push yesterday.

[Copilot]

Pull Request Overview

This pull request addresses a warning triggered by the use of an integer literal for initializing a thread identifier by switching to value initialization.

• Replace "pthread_t threadHandle = 0;" with "pthread_t threadHandle = {};" to zero-initialize the thread id variable and eliminate the warning.

[seanm]

IIRC pthread_t is not a pointer on all platforms, I remember fixing this myself once, then having to back out of it...

I have a branch where I started on #3136 which would fix the issue in a different way.

[jhlegarreta]

@seanm thanks for this additional information; until your fixes land in the code base, can you please try building locally with this patch set? If the warning goes away, I would prefer to have this merged to lower the noise from the dashboard.

[seanm]

I've finally caught up on all my ITK github emails, and see only now that you changed this to not use nullptr. This new way is probably fine.

IIRC this was the last -Wzero-as-null-pointer-constant in ITK!

[seanm]

Tried locally, I see just one more (though of course I did not build every possible module or permutation):

ITK/Modules/Core/Common/include/itkThreadSupport.h:45:55: warning: zero as null pointer constant [-Wzero-as-null-pointer-constant]
   45 | constexpr ThreadProcessIdType ITK_DEFAULT_THREAD_ID = 0;
      |                                                       ^
      |                                                       nullptr

Want to amend this PR to fix that one too?

[jhlegarreta]

Re: #5419 (comment) commit amended, force pushed. Thanks for having tried this @seanm.

[hjmjohnson]

IIRC pthread_t is not a pointer on all platforms, I remember fixing this myself once, then having to back out of it...

I have a branch where I started on #3136 which would fix the issue in a different way.

I have the same recollection. I've had to back out that change in the past as well.

It would be great to have the proper #ifdef initializaitons for when it is needed to be 0 and when it should be nullptr.

[jhlegarreta]

/azp run ITK.Windows