Re: [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, May 16, 2025 at 06:26:23PM +0200, Stefano Brivio wrote:
> On Fri, 16 May 2025 17:25:21 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Thu, May 15, 2025 at 06:05:01PM +0200, Stefano Brivio wrote:
> > > Cppcheck 2.14.2 on Alpine Linux (musl) says that:
> > > 
> > > tap.c:111:19: error: Found an exit path from function with non-void return type that has missing return statement [missingReturn]
> > >  switch (c->mode) {
> > >                   ^
> > > 
> > > This exit path is not reachable because we ASSERT(0) after the switch,
> > > but for some reason cppcheck doesn't see this with musl headers. Hide
> > > the warning with a redundant return statement.
> > > 
> > > Signed-off-by: Stefano Brivio <sbrivio@redhat.com>  
> > 
> > Hm.  Alternatively you could change this to call abort_with_msg()
> > directly.  That's marked as ((noreturn)) so with any luck cppcheck
> > will then be able to figure out what's going on.  Although, I'm
> > slightly surprised it can't do so already: I thought I put the
> > ((noreturn)) in there to avoid warnings exactly like this.
> 
> So, I checked, and abort_with_msg(""); works. ASSERT() ultimately
> expands to abort_with_msg(), but for some reason cppcheck together with
> Clang can't "follow" that, I suppose it's something related to the
> pre-processor.
> 
> But in any case, abort_with_msg("") doesn't look as descriptive and
> as obviously redundant as a return statement with a comment, so I don't
> quite see the benefit changing it (also considering that I need to test
> other versions, which takes time).

Well, kind of the whole point of abort_with_msg() is that you can give
it a meaningful message, which might change the picture.  It would
also be trivial to write an unreachable() wrapper around that.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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