* [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()
@ 2025-05-15 16:05 Stefano Brivio
2025-05-16 7:25 ` David Gibson
0 siblings, 1 reply; 5+ messages in thread
From: Stefano Brivio @ 2025-05-15 16:05 UTC (permalink / raw)
To: passt-dev
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>
---
tap.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/tap.c b/tap.c
index d630f6d..6db5d88 100644
--- a/tap.c
+++ b/tap.c
@@ -118,6 +118,8 @@ unsigned long tap_l2_max_len(const struct ctx *c)
}
/* NOLINTEND(bugprone-branch-clone) */
ASSERT(0);
+
+ return 0; /* Unreachable, for cppcheck's sake */
}
/**
--
@@ -118,6 +118,8 @@ unsigned long tap_l2_max_len(const struct ctx *c)
}
/* NOLINTEND(bugprone-branch-clone) */
ASSERT(0);
+
+ return 0; /* Unreachable, for cppcheck's sake */
}
/**
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()
2025-05-15 16:05 [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len() Stefano Brivio
@ 2025-05-16 7:25 ` David Gibson
2025-05-16 16:26 ` Stefano Brivio
0 siblings, 1 reply; 5+ messages in thread
From: David Gibson @ 2025-05-16 7:25 UTC (permalink / raw)
To: Stefano Brivio; +Cc: passt-dev
[-- Attachment #1: Type: text/plain, Size: 1461 bytes --]
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.
> ---
> tap.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/tap.c b/tap.c
> index d630f6d..6db5d88 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -118,6 +118,8 @@ unsigned long tap_l2_max_len(const struct ctx *c)
> }
> /* NOLINTEND(bugprone-branch-clone) */
> ASSERT(0);
> +
> + return 0; /* Unreachable, for cppcheck's sake */
> }
>
> /**
--
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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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()
2025-05-16 7:25 ` David Gibson
@ 2025-05-16 16:26 ` Stefano Brivio
2025-05-17 10:29 ` David Gibson
0 siblings, 1 reply; 5+ messages in thread
From: Stefano Brivio @ 2025-05-16 16:26 UTC (permalink / raw)
To: David Gibson; +Cc: passt-dev
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).
--
Stefano
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()
2025-05-16 16:26 ` Stefano Brivio
@ 2025-05-17 10:29 ` David Gibson
2025-05-19 7:27 ` Stefano Brivio
0 siblings, 1 reply; 5+ messages in thread
From: David Gibson @ 2025-05-17 10:29 UTC (permalink / raw)
To: Stefano Brivio; +Cc: passt-dev
[-- Attachment #1: Type: text/plain, Size: 2023 bytes --]
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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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len()
2025-05-17 10:29 ` David Gibson
@ 2025-05-19 7:27 ` Stefano Brivio
0 siblings, 0 replies; 5+ messages in thread
From: Stefano Brivio @ 2025-05-19 7:27 UTC (permalink / raw)
To: David Gibson; +Cc: passt-dev
On Sat, 17 May 2025 20:29:20 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> 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.
Right, but I was struggling with making it meaningful: "dodged cppcheck
warning, you'll never see this"? I much prefer a return with a comment.
> It would
> also be trivial to write an unreachable() wrapper around that.
Ah, that would be nice, yes. I would consider writing one after 2-3
more cases like this.
--
Stefano
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-05-19 7:27 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2025-05-15 16:05 [PATCH] tap: Avoid bogus missingReturn cppcheck warning in tap_l2_max_len() Stefano Brivio
2025-05-16 7:25 ` David Gibson
2025-05-16 16:26 ` Stefano Brivio
2025-05-17 10:29 ` David Gibson
2025-05-19 7:27 ` Stefano Brivio
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