meson.build: raise used C standard to C11

[ziyao233]

Some C11 features have been used, but meson.build still specifies c_std=c99, leading to errors on Clang compiler.

Fixes: #364

[cgwalters]

Thanks for this! Actually testing with a somewhat recent clang (clang version 18.1.8) here I get compilation failures.

I went ahead and pushed a few additional commits that add a CI check with clang and also fix those errors.

[cgwalters]

Also same question as the other PR re licensing: #344
Are you OK with those license terms?

[ziyao233]

Also same question as the other PR re licensing: #344
Are you OK with those license terms?

It's okay to me :)

[cgwalters]

I pushed some other changes here so I probably shouldn't merge without a 3rd reviewer.

[cgwalters]

Especially the ioctl changes need careful review, I only sanity checked this. Hmm I may just mark as draft until we've done that.

@ziyao233 what version of clang are you using? It must be an older version that doesn't warn about some gnu-specific stuff?

Ohh or maybe the conceptual problem is those are just warnings but in CI we use -Werror, and so my attempt to add CI coverage clashed with that. Let me see...perhaps should just take your change as is and I'll split my patches to a separate PR.

[ziyao233]

Especially the ioctl changes need careful review, I only sanity checked this. Hmm I may just mark as draft until we've done that.

@ziyao233 what version of clang are you using? It must be an older version that doesn't warn about some gnu-specific stuff?

Exactly 18.1.8 and it does throw some warnings, but I didnt come up with a graceful solution to some of them, especially fsverity related things. I decided to split warning fixes into another PR (they are just causing warnings but not error).

Ohh or maybe the conceptual problem is those are just warnings

Yep

but in CI we use -Werror, and so my attempt to add CI coverage clashed with that. Let me see...perhaps should just take your change as is and I'll split my patches to a separate PR.

seems a good idea to me