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<div class="moz-cite-prefix">On 11/17/13 08:31, Renato Golin wrote:<br>
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<div class="gmail_quote">On 17 November 2013 15:45, Behan
Webster <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:behanw@converseincode.com" target="_blank">behanw@converseincode.com</a>></span>
wrote:<br>
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<div>So, in that case, you could have an #elif
__gcc with the GCC case and an #else with an
error message "Compiler doesnt support
builtin_whatever". Once the builtin is
accepted on both compilers, you can merge
them all, but still leave the #error, so
that new compilers will have a very nice
message telling them to implement the
builtin.</div>
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Hm. I see what you're suggesting. I suppose that would
work.</div>
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<div class="gmail_extra">I believe all compilers that claim GCC
compatibility, including older versions of GCC, will set the
same flags, so #ifs and #ifdefs should work with them. If the
kernel is currently compiled with the "alternatives", it
should just continue to do so.</div>
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<div class="gmail_extra">The problem arises if there are other
compilers building the kernel that don't define __gcc etc BUT
implement the necessary GCC-extensions (proprietary ones, like
icc). My guess is that there aren't that many proprietary
compilers that try to compile the kernel, but that could be an
issue upstream.</div>
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I don't know what icc does, and that theoretically still works (icc
is still technically/theoretically the "second compiler" for the
kernel). So I still lean to having the default case be the status
quo (at least for the moment).<br>
<br>
My feeling at this point is enabling clang without breaking gcc (or
anything else) is more important than absolute correctness.
Essentially we need patches to be as easy to upstream as we can make
them, with little to no breakage. Part of this is putting clang in
the best possible light with little to no downside (breakage is a
perceived downside). As much as I personally would prefer to have
the kernel code follow the standard, as you know, it's not our call.
I've used too many compilers to count, and so I personally
appreciate standards based C code tremendously!<br>
<br>
Correctness will come. Especially when you end up with large bodies
of people using clang with the kernel code (and not just gcc). Those
are the people whom we are trying to enable. :)<br>
<br>
As far as icc is concerned we don't have the means to test our
patches with it. The reality is that, while most devs are aware of
icc, almost none of them give icc any thought when it comes to their
code. Since few have access to icc, the feeling seems to be that if
code breaks for icc, someone else will fix it. This is hardly ideal.<br>
<br>
I'm hoping that clang will become the "theoretical" second compiler.
Essentially since both gcc and clang are now easily installable with
your distro (or from llvm.org) that checking your code with either
is straightforward. This will not only allow more people to use
clang instead of gcc as their primary compiler, but also allow
people who normally use gcc to also test with clang (if they choose
to). I can imagine a future where testing with both gcc and clang
before you upstream is encouraged. :)<br>
<br>
I understand that icc now uses the clang frontend for their
compiler. So it seems that by enabling clang in the kernel we're
likely also helping icc (which will also help our efforts).<br>
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<div class="gmail_extra">All that said, this is just bad
practice, not broken code. So don't sweat too much about it.
;)</div>
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Exactly. :)<br>
<br>
Behan<br>
<pre class="moz-signature" cols="72">--
Behan Webster
<a class="moz-txt-link-abbreviated" href="mailto:behanw@converseincode.com">behanw@converseincode.com</a></pre>
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