Re: [PATCH 1/1] meson: Enable -Wshadow=local

[Thomas Huth]

On 26/10/2023 07.51, Warner Losh wrote:
> On Wed, Oct 25, 2023, 11:31 PM Markus Armbruster <armbru@redhat.com 
> <mailto:armbru@redhat.com>> wrote:
>
>     Local variables shadowing other local variables or parameters make the
>     code needlessly hard to understand.  Bugs love to hide in such code.
>     Evidence: commit bbde656263d (migration/rdma: Fix save_page method to
>     fail on polling error).
>
>     Enable -Wshadow=local to prevent such issues.  Possible thanks to
>     recent cleanups.  Enabling -Wshadow would prevent more issues, but
>     we're not yet ready for that.
>
>     As usual, the warning is only enabled when the compiler recognizes it.
>     GCC does, Clang doesn't.
>
>     Some shadowed locals remain in bsd-user.  Since BSD prefers Clang,
>     let's not wait for its cleanup.
>
>     Signed-off-by: Markus Armbruster <armbru@redhat.com
>     <mailto:armbru@redhat.com>>
>     ---
>       meson.build | 1 +
>       1 file changed, 1 insertion(+)
>
>     diff --git a/meson.build b/meson.build
>     index dcef8b1e79..89220443b8 100644
>     --- a/meson.build
>     +++ b/meson.build
>     @@ -462,6 +462,7 @@ warn_flags = [
>         '-Wno-tautological-type-limit-compare',
>         '-Wno-psabi',
>         '-Wno-gnu-variable-sized-type-not-at-end',
>     +  '-Wshadow=local',
>
>
> Does this work with clang? I've not had good luck enabling it.

The flags are added via cc.get_supported_arguments(warn_flags), so meson 
checks whether the compiler supports them before blindly adding them to the 
list.
That means it should get ignored with Clang, i.e. we should be ok for the 
remaining spots in the bsd-user code, assuming that most FreeBSD users will 
use Clang to compile QEMU.

 Thomas