Provide clearenv?

[shahn]

Can clearenv() be supported, with a workaround of environ = NULL where it's not supported?

[fiveop]

Certainly (at least for the first part). You would need to add bindings for clearenv to the project libc and then add a wrapper to nix.

As for the latter part, you would need to figure out (for each platform) how to implement clearenv given the capabilities provided by libc.

[Susurrus]

clearenv is already in libc, so this just needs a safe wrapper.

[wginolas]

I am thinking about implementing this feature, but I am not sure where to add the cleanenv () implementation. Are there any other functions concerning environment variables?

[Susurrus]

Cool, it'd be great to implement this! If you look at the man page, you'll see that clearenv(3) is a Linux-only API, but it has a few sibling functions that should also be implemented and are POSIX: getenv(3), putenv(3), setenv(3), and unsetenv(3).

As to where to put these functions, we normally put functions into files following their location within libc (you can use the manpages to figure out which files functions are in). But for stdlib.h we've been splitting up the stdlib.h header into separate files, and I think it makes sense to continue this. I'd suggest you put all these functions into a src/env.rs file.

And if you get stuck while writing code, I'd suggest submitting a draft PR (put [WIP] in the title if you don't want us to comment yet and are just running CI or the like) and we'll review it rather than continuing discussion here.

[jorickert]

Hello im planning to work on this functions. getenv(3), putenv(3), setenv(3), and unsetenv(3) seem to be easy, but i have a questions regarding clearenv(3).
This functions returns a success with 0, error with something else, but it does not set errno. What is the best way to return this in rust? Option<()>, Result<()> or a bool ?

[asomers]

It can return an error, but doesn't set errno? Sounds a little useless. How would you diagnose the problem? Ahh, I see. It never actually returns anything but 0.
https://github.com/lattera/glibc/blob/a2f34833b1042d5d8eeb263b4cf4caaea138c4ad/stdlib/setenv.c#L354
https://github.com/kraj/uClibc/blob/ca1c74d67dd115d059a875150e10b8560a9c35a8/libc/stdlib/setenv.c#L166

Nonetheless, Rust prefers using Result over bool anytime errors are in play. It's more self-documenting, for one thing. Also, Result is a must_use type, so you'll get a compiler warning if you don't check the return value. I would use Result<(), ()>.