[review request] Remove "old-style" flexible array usage in ZFS.

[Matthew Ahrens via illumos-zfs]

https://reviews.csiden.org/r/63/

In dnode\_children\_t, use C99's "\[\]" idiom for declaring the
variable sized array dnc\_children at the end of the structure.
This prevents the compiler from mistakenly optimizing away
accesses beyond the array's defined size.

--matt



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[Matthew Ahrens via illumos-zfs]

Makes sense. I'd never heard of unnamed structs and unions before now --
must be a GCC-ism. I think we want to stick with c99 in illumos (and I'm
sure FreeBSD also wants to avoid GCC-specific language extensions since
they compile the kernel with clang). But we could accomplish the same
thing in c99 with a more verbose change. Patches welcome :-)

--matt

On a similar note, you may want to take a look at this patch we landed
https://github.com/zfsonlinux/zfs/commit/aca19e0
--
Cheers, Prakash

[1]https://reviews.csiden.org/r/63/
In dnode\_children\_t, use C99's "\[\]" idiom for declaring the
variable sized array dnc\_children at the end of the structure.
This prevents the compiler from mistakenly optimizing away
accesses beyond the array's defined size.
--matt
References
1. https://reviews.csiden.org/r/63/
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[Carson Gaspar via illumos-zfs]

Post by Matthew Ahrens via illumos-zfs
Makes sense. I'd never heard of unnamed structs and unions before now
-- must be a GCC-ism. I think we want to stick with c99 in illumos (and
I'm sure FreeBSD also wants to avoid GCC-specific language extensions
since they compile the kernel with clang). But we could accomplish the
same thing in c99 with a more verbose change. Patches welcome :-)

They are C11, FYI. Solaris Studio has support in 12.4 beta, but still
won't handle some nested constructs that gcc does. I have no idea where
clang is...

I agree that sticking to C99 is the sensible approach.

[Prakash Surya via illumos-zfs]

On a similar note, you may want to take a look at this patch we landed
on the Linux port. It also deals with compiler array optimizations:

https://github.com/zfsonlinux/zfs/commit/aca19e0
--
Cheers, Prakash

[1]https://reviews.csiden.org/r/63/
In dnode\_children\_t, use C99's "\[\]" idiom for declaring the
variable sized array dnc\_children at the end of the structure.
This prevents the compiler from mistakenly optimizing away
accesses beyond the array's defined size.
--matt
References
1. https://reviews.csiden.org/r/63/
_______________________________________________
developer mailing list
http://lists.open-zfs.org/mailman/listinfo/developer