clarify when reading uninititalized memory is allowed #852
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| @@ -57,6 +57,11 @@ code. | |||
| > **Note**: `rustc` achieves this with the unstable | |||
| > `rustc_layout_scalar_valid_range_*` attributes. | |||
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| Note that uninitialized memory is also implicitly invalid for any type that has | |||
| a restricted set of valid values. In other words, the only cases in which | |||
| reading uninitialized memory is permitted is inside `union`s, and between the | |||
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You can probably just minimize the second part to just "padding". We also don't define "compound type" anywhere, so it's probably best not to use it. We do define "user defined type" for struct/enum/union though.
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It's all "types with fields" though that I mean by "compound type" -- so, including tuples and arrays.
Co-authored-by: Ryan Scheel <Ryan.havvy@gmail.com>
I tried rewording that, what do you think? |
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LGTM except the one nit.
I don't really like using parentheticals, but a quick search for padding in the reference, and we don't say much about its properties at all. I'm going to file a follow-up issue for properly explaining it.
If you can merge this yourself, r=me after the suggested change.
Co-authored-by: Ryan Scheel <Ryan.havvy@gmail.com>
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@Havvy I don't have merge permissions in this repo. |
Update books ## reference 4 commits in 1b6c4b0afab97c0230433466c97167bbbe8445f6..25391dba46262f882fa846beefaff54a966a8fa5 2020-08-18 17:04:28 -0700 to 2020-09-02 07:22:55 -0700 - clarify when reading uninititalized memory is allowed (rust-lang/reference#852) - Update patterns chapter, add rest patterns. (rust-lang/reference#876) - Improve Type-Coersion Documentation (rust-lang/reference#843) - Added variable back into example. (rust-lang/reference#880) ## book 3 commits in c0a6a61b8205da14ac955425f74258ffd8ee065d..e5ed97128302d5fa45dbac0e64426bc7649a558c 2020-08-14 14:21:49 -0500 to 2020-08-31 12:53:40 -0500 - Fix type mismatch in listing 10-5 (rust-lang/book#2441) - Update ppendix-06-translation.md (rust-lang/book#2437) - Correct no-listing-10-result-in-tests: Take tests module out of the main function (rust-lang/book#2430) ## rust-by-example 3 commits in 80a10e22140e28392b99d24ed02f4c6d8cb770a0..19f0a0372af497b34369cf182d9d16156cab2969 2020-08-08 09:56:46 -0300 to 2020-08-26 09:38:48 -0300 - prefer `length` over `size` when talking about number of elements vs. bytesize (rust-lang/rust-by-example#1372) - Split out variable shadowing into a separate example (rust-lang/rust-by-example#1370) - Update extern crate related sections (rust-lang/rust-by-example#1369) ## edition-guide 1 commits in bd6e4a9f59c5c1545f572266af77f5c7a5bad6d1..81f16863014de60b53de401d71ff904d163ee030 2020-07-12 17:37:08 -0500 to 2020-08-27 13:56:31 -0700 - Fix a small typo. (rust-lang/edition-guide#218)
This should hopefully help avoid confusion like this one.