Right.  If this had been done correctly (i.e. implicit) in the first
place, the referenced ticket would never have had a bug.

I cannot think of a reason to ever use explicit access.  Perhaps in the
early days of 32/64 conversion when a 32-bit API might need to be accessed.

I agree, there's no need to rush this into place, but I think it greatly
reduces the chances of bugs and should simplify the code.

"(implicit) 3. The size of filesize related data types is increased to 64 bits. eg off_t, blkcnt_t, etc are now 64 bits in size"

Since explicit was used, the size of off_t may be different on 32-bit systems.

-tecra:$ egrep -l off_t */*.c */*.h
generic/tclIOUtil.c
macosx/tclMacOSXFCmd.c  # 64-bit, no issue here.
unix/tclUnixChan.c
generic/regex.h
unix/tclUnixPort.h
-tecra:$ egrep -l blkcnt_t */*.c */*.h
generic/tclIOUtil.c