On Tue, Aug 19, 2025 at 04:06:45PM +0100, Peter Maydell wrote:
> On Tue, 19 Aug 2025 at 16:04, Pierrick Bouvier
> <pierrick.bouv...@linaro.org> wrote:
> >
> > On 8/19/25 6:24 AM, Peter Maydell wrote:
> > > On Fri, 8 Aug 2025 at 07:55, Mohamed Mediouni <moha...@unpredictable.fr>
> > > wrote:
> > > Can you follow the QEMU coding style, please (here and elsewhere)?
> > > Variables and function names should be all lower case,
> > > and variable declarations go at the start of a C code
> > > block, not in the middle of one.
> > >
> >
> > In some cases, including in this function, I feel that the rule to
> > declare variables at the start of a block is not really helpful, and is
> > more related to legacy C than a real point nowadays.
> > As well, it sometimes forces to reuse some variables between various sub
> > blocks, which definitely can create bugs.
> >
> > Anyway, I'm not discussing the existing QEMU coding style, but just
> > asking if for the current context, is it really a problem to declare
> > variable here?
>
> The point of a coding style is to aim for consistency. QEMU
> is pretty terrible at being consistent, but we should try.
> The rule about variables at start of block is not because
> some compilers fail to compile it, but because we think
> it's overall more readable that way.
There are also potential[1] functional problems with not declaring
at the start of block, because if you have a "goto cleanup" which
jumps over the line of the declaration, the variable will have
undefined state when the 'cleanup:' block is running. This is
something which is very subtle and easily missed when reading the
code flow.
With regards,
Daniel
[1] I say "potential" because we unconditionally build with
-ftrivial-auto-var-init=zero to mitigate this danger
in practice.
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