[cfe-dev] -Wunreachable-code vs -Wcovered-switch-default

David Blaikie dblaikie at gmail.com
Tue Sep 11 08:05:01 PDT 2012

On Tue, Sep 11, 2012 at 12:40 AM, Magnus Reftel <magnus.reftel at gmail.com> wrote:
> Hi all,
> consider the following example code:
> #include <stdlib.h>
> enum e {E1, E2};
> int main(int argc, char* argv[])
> {
>         enum e e = atoi(argv[argc-1]);
>         switch(e)
>         {
>                 case E1: return 1;
>                 case E2: return 2;
>                 default: return 3;
>         }
> }
> If compiled with Clang with -Wcovered-switch-default, it rightly warns
> about the default case. This can be suppressed when intentional by
> using -Wno-covered-switch-default. If compiled with
> -Wunreachable-code, it will also warn on that line, but it seems that
> that warning cannot be silenced when intentional without also
> silencing all other occurrences of unreachable code in the file
> ("-Wunreachable-code -Wno-covered-switch-default" still warns).
> I'd like to get warnings if there is unreachable code in the general
> case, but not have it warn on covered switch defaults. Is there a way
> of accomplishing that?

Not just yet, but there probably should be.

I've been working on & off (more off) on improving the underlying
infrastructure for this warning to allow more precision that would
also be a necessary prerequisite to the improvement you've described.
So it's a bit of a ways off yet, but we shouldn't lose track of it.

If you'd like to file a bug (llvm.org/bugs) and assign it to me,
that'd be great.

- David

> Best Regards
> Magnus Reftel
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