Make a new attribute for the #[link_name = ""] special case

[brson]

[link_name = ""] is used to tell rustc not to issue the -L linker flag. This is a special case of the link_name flag so let's replace it with its own attribute, like #[nolink].

[gmfawcett]

I'd like to try this. Would #[link_name = ""] still be acceptable, or should it result in an error?

[brson]

My opinion is that #[link_name = ""] should go away.

[brson]

In that case yes, it would have to be an error.

[gmfawcett]

OK, I implemented #[nolink](except for making #[link_name=""] an error), then updated the tests to use #[nolink], and got green lights under "make check." But when I try to update the stdlib (say, std::linux_os), it adds a "-llibc" flag, and fails. If I understand correctly, this is because "make check" builds libruststd.so before building my updated rustc.

Should I just leave the stdlib alone? Will your staged compilers eventually learn how to do #[nolink], and then you'd update the stdlib? Or, how can I build a stage N rustc without first building the stage N stdlib?

[brson]

Probably the way to do this is use both #[link_name = ""] and #[nolink] in std (and core possibly?) with a FIXME to remove link_name later. Then we'll snapshot the compiler that knows about #[nolink], remove link_name, then make #[link_name = ""] an error.

[gmfawcett]

Good idea. OK, let me prepare a pull request.

[gmfawcett]

Pull request sent.