Increase libthr WARNS to the default of 6, and fix the warnings

[vangyzen]

Summary

Increase libthr WARNS to the default of 6, and fix the warnings

Fix warnings about:

• casting away volatile and const
• unused parameters
• a variable in a macro shadowing a local in a calling function
• no previous 'extern' declaration for non-static variable
• others as explained by #pragmas and comments

These have no effect, except for removing an unused parameter.

[vangyzen]

I've just realized that all of the #pragma GCC should probably be #pragma clang.

[kib]

Perhaps commit the changes which do not cause a discussion, now, to reduce the patch size.

lib/libc/include/spinlock.h

47 ↗

(On Diff #28541)

Arguably, if fname is not volatile, lineno could be as well.

That said, debugging 'support' for libc spinlocks was never used for last 10-15 years, I suggest to remove it at all.

lib/libthr/thread/thr_mutex.c

772 ↗

(On Diff #28541)

I argue that whole libthr should be compiled with this warning disabled. It is the only reasonable approach for the code which implements the locks. In other words, I suggest to move the warning disabling flag into libthr Makefile.

lib/libthr/thread/thr_rwlock.c

63 ↗

(On Diff #28541)

I think it is not too hard to replace the macro use with static (might be inline) initializer function.

[vangyzen]

lib/libc/include/spinlock.h

47 ↗

(On Diff #28541)

I kept this minimal to keep the patch small. As you suggest, I'll remove this code in a separate commit.

lib/libthr/thread/thr_mutex.c

772 ↗

(On Diff #28541)

Yes, I tend to agree. Although the warnings might be helpful in some files, the chance of false positives is too high.

lib/libthr/thread/thr_rwlock.c

63 ↗

(On Diff #28541)

Agreed, and I would strongly prefer that. As before, it will be a separate commit.