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Improve safety & usability of |size_t| and |ssize_t|. - #29222

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Improve safety & usability of |size_t| and |ssize_t|.#29222
briansmith wants to merge 4 commits into
rust-lang:masterfrom
briansmith:size_t_ssize_t

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@briansmith

@briansmithbriansmith commented Oct 22, 2015

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This has been rebased on top of #28779 and #29220. It is intended to address the usize/isize related aspects of RFC 1291.

Note in particular that one of these changesets removes casts that would actually result in unsafe memory usage on any platform where libc::size_t is smaller than usize.

r? @alexcrichton

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rust-highfive commented Oct 22, 2015

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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

@briansmith

briansmith commented Oct 22, 2015

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@bors r? @alexcrichton

@bors

bors commented Oct 22, 2015

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☔ The latest upstream changes (presumably #29045) made this pull request unmergeable. Please resolve the merge conflicts.

@briansmith
Add additional automatic conversions to usize/isize.
0f2eaa2
Also, improve the documentation related to the range of usize and
isize.
@briansmith
Improve safety & usability of |size_t| and |ssize_t|.
efdc16b
@briansmith
Remove dangerous and unnecessary casts of |usize| to |libc::size_t|.
e2311fc
Since |usize| may be larger than |libc::size_t|, it is generally not safe to
cast from |usize| to |libc::size_t|.
The effect of this commit is to cause the build to fail on a platform where
`libc::size_t` isn't the same as `usize`. But, that is better than the current
state of affairs, where unsafe truncations can occur on such platforms,
potentially leading to buffer overflows and other unsafety.
@briansmith
Remove some now-unnecessary casts of |size_t| to |usize|.
5864ba9
I didn't try to find every such cast. I concentrated on the files that
had now-unnecessary casts from |usize| to |size_t|.
@briansmith

briansmith commented Oct 22, 2015

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This is now against the wrong repo.

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@briansmith@rust-highfive@bors@alexcrichton