[libc++][format] Make public functions nodiscard.

[Mordante]

Summary

This is an extension and only adds the functions that are a considered a
but when called and ignoring the result.

Drive-by sort all nodiscard extensions in the documentation.

[Mordante]

CI fixes.

[philnik]

libcxx/test/libcxx/diagnostics/format.nodiscard_extensions.compile.pass.cpp

3

You seem to be missing a positive test.

libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp

27–28

Why not simply cast to void?

[Mordante]

Thanks for the review!

libcxx/test/libcxx/diagnostics/format.nodiscard_extensions.compile.pass.cpp

3

Nice catch, I'll commit my local file this time ;-)

libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp

27–28

I prefer name instead of a magic invocation, @BillyONeal spend the effort to change them in D40065.

[Mordante]

Addresses review comments.

[philnik]

libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp

27–28

IMO it's kind-of pointless to have a macro that just casts to void, since its people know what casting to void means, but not what a given macro actually does. It looks to me like the macro does something magical to check that it's actually ignoring nodiscard.

[Mordante]

Thanks for the review!

libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp

27–28

I like he macro since it explains why it's needed.