spa: avoid type narrowing warning

[rlibby]

Building the spa module for i386 caused gcc to emit
-Wint-to-pointer-cast "cast to pointer from integer of different size"
because spa.spa_did was uint64_t but pthread_join (via thread_join in
spa_deactivate) takes a pointer (32-bit on i386). Define spa_did to be
pointer-size instead. For now spa_did is in fact never non-zero and the
thread_join could instead be ifdef'd out, but changing the size of
spa_did may be more useful for the future.

Signed-off-by: Ryan Libby [email protected]

Motivation and Context

Part of a small set of changes for building with gcc on FreeBSD.

This addresses an issue with the amd64 gcc build on FreeBSD. When gcc builds the spa module for i386 it emits the following warning due to the size difference between uint64_t and pthread_t:

Building /usr/obj/gcc6/usr/src/freebsd/amd64.amd64/obj-lib32/cddl/lib/libzpool/spa.o
In file included from /usr/src/freebsd/sys/contrib/openzfs/module/zfs/spa.c:45:0:
/usr/src/freebsd/sys/contrib/openzfs/module/zfs/spa.c: In function 'spa_deactivate':
/usr/src/freebsd/sys/contrib/openzfs/include/sys/zfs_context.h:235:37: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
 #define thread_join(t) pthread_join((pthread_t)(t), NULL)
                                     ^
/usr/src/freebsd/sys/contrib/openzfs/module/zfs/spa.c:1388:3: note: in expansion of macro 'thread_join'
   thread_join(spa->spa_did);
   ^~~~~~~~~~~

Description

The solution here is to define spa_did as uintptr_t, which will match pointer size, avoiding the warning. In fact, for now, spa_did is never assigned non-zero because the code is ifdef'd out. Even in the ifdef'd code, it is never assigned a pthread_t, but only a kernel thread id. Perhaps this may change in the future. Regardless, neither a kernel thread id nor a pthread_t should be larger than uintptr_t.

How Has This Been Tested?

Compile tested in the downstream FreeBSD build with gcc and clang.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.