[PATCH] Introduce -Wimplicit-fallthrough={0,1,2,3,4,5}

Allan Sandfeld Jensen linux@carewolf.com
Thu Oct 13 14:53:00 GMT 2016

On Tuesday 11 October 2016, Jakub Jelinek wrote:
> Hi!
> The following patch introduces difference warning levels for
> -Wimplicit-fallthrough warning, so projects can choose if they want to
> honor only attributes (-Wimplicit-fallthrough=5), or what kind of comments.
> =4 is very picky and accepts only very small amount of comments, =3 is what
> we had before this patch, =2 looks case insensitively for falls?[
> \t-]*thr(u|ough) anywhere in the comment, =1 accepts any comment, =0 is
> the same as -Wno-implicit-fallthrough - disables the warning.

I would suggest also looking for comments with "no break" in them, as that is 
another common way to annotate the intentional lack of a 'break'.

If you want another example besides the linux kernel, I unified all our fall 
through comments in qtbase in August: 

Though Qt is far from -Wimpliciit-fallthough clean after that, another 
colleague is working on that since we have traditionally aimed for -Wall -
Wextra -Werror, though it will seriously wreck hawock with readability in 
several places with unrolled loops and switches on integers.

Best regards

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