realpath in stdlib.h but not in library about wasi-libc HOT 7 CLOSED

Yeah, WASI doesn't have absolute paths, so the standard realpath doesn't fit. I filed #82 to remove the declarations.

That said, besides making paths absolute, realpath also resolves symbolic links, resolves .. and . paths, and trims redundant / characters. We could conceivably have a realpath which does those things and maybe also resolves relative paths to be rooted at ., which might be enough for some use cases.

from wasi-libc.

It doesn't have absolute paths at the syscall layer, but doesn't it kind of emulate them in libpreopen? I mean if the concept of PWD exists then can't realpath just use getcwd() to construct an abspath?

from wasi-libc.

We don't currently have getcwd either :-). libpreopen maps from absolute path to base + relative path, which isn't enough to do getcwd.

Should we add a getcwd? It does leak information about the host, and we can't easily virtualize or remap it because the main purpose is to get a string that you can send to another process or serialize out somewhere to be read by the outside world, so it has to reflect the actual host path name.

from wasi-libc.

I think we should encourage the programs that require these sort of absolute path functions to implement them totally in userland, if possible. I wouldn't want to expose the host's "real" cwd at all, but it should be possible to define these functions such that it always pretends to be under /home/wasi or something, right?

from wasi-libc.

No, I'm not talking about exposing the real host cwd. But we can build cwd in userspace based on the pre-opened root fd can't we? I'm surprised libpreopen doesn't do this already. Wouldn'tit be as simple as doing: base + global_cwd + relative?

I don't understand what you mean about sending the string to the outside world. Paths only make sense within a given module, right? Or at least within modules that shared the same virtualized view of the filesystem.

from wasi-libc.

Right, I'd imagine it would be similar to running in a chroot.

from wasi-libc.

The original issue here is fixed in a413650; we no longer declare realpath.

If anyone's interested in introducing a concept of a cwd, even without exposing the host cwd, we'd need new WASI support, so we should discuss this in the WASI issue tracker.

from wasi-libc.