Point out str::as_ptr is not nul-terminated

[lukaslueg]

Adds a paragraph to the documentation of str::as_ptr() and str::as_mut_ptr() (and by extension String) pointing out that the pointer can not be used as a C-like string; trying to do so in FFI will result in hilarity.

[rust-highfive]

r? @joshtriplett

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[rust-log-analyzer]

The job x86_64-gnu-llvm-10 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

Set({"src/doc/edition-guide"}) not skipped for "bootstrap::doc::EditionGuide" -- not in ["src/tools/tidy"]
Rustbook (x86_64-unknown-linux-gnu) - edition-guide
Building stage0 tool linkchecker (x86_64-unknown-linux-gnu)
    Finished release [optimized] target(s) in 0.12s
std/string/struct.String.html:858: broken link - `std/std/ffi/struct.CString.html`
std/string/struct.String.html:872: broken link - `std/std/ffi/struct.CString.html`
number of HTML files scanned: 28420
number of HTML redirects found: 8894
number of links checked: 1608984
number of links ignored due to external: 65111

[lukaslueg]

What's the policy on links from core (where str lives) to std (where CString lives). Should I just unlink the reference?

[the8472]

You can specify them as a path to the generated doc html file instead. grep for ../../ to find some examples. To verify that the link works you can run ./x.py test linkchecker library/std --stage 0.

[lukaslueg]

Ah, it seems the problem is that the link is included in the docs for core::str and std::String (due to the deref-impl). A link of the form "../../std" either breaks for the former or the latter.

[joshtriplett]

This change seems reasonable to me. r=me when CI passes.

[lukaslueg]

I'll need a hint on how to solve the linking catch 22. It seems to me a direct link to CString (../../....) is needed as str lives in core, while CString lives in std. But String has a Deref<Target=str>, and the link that is valid from core::str to std::CString is not valid from std::String to std::CString. I could also simply remove the direct link.

[JohnCSimon]

ping from triage:
@lukaslueg
Returning to you to address build failures and after that, please switch back to S-waiting-on-review.
thanks.

@rustbot label: +S-waiting-on-author -S-waiting-on-review

[JohnCSimon]

ping from triage:
@lukaslueg can you post your status on this PR? Thank you.

[lukaslueg]

@JohnCSimon As in my previous comment: I'll need a hint on how to solve the intra-doc-linking issue that arose here: A direct link from str to CString (via ../../....) is needed as str lives in core while CString lives in std. But String has a Deref<Target=str>, and the hard-link that is valid from core::str to std::CString is not valid from std::String -> Deref<str> to std::CString. I could also simply remove the intra-doc link if there is no solution to this.

[JohnCSimon]

@RalfJung @Manishearth can you help with this?

[Manishearth]

@jyn514 I forgot what the current status of core-to-std intra links was, overall I'm fine with allowlisting this if we have to

[jyn514]

No, there's no way to link from core to std with intra-doc links. #74481
You'll have to add it to the ignored errors in the linkchecker.

[JohnCSimon]

Ping from triage:
@lukaslueg PR hasnt been touched in three months. Closing as inactive, feel free to reopen.

@rustbot label: +S-inactive