improve error message shown for unsafe operations #52207
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…ned behavior could arise Inspired by @gnzlbg at rust-lang#46043 (comment)
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| = note: fields of packed structs might be misaligned: dereferencing a misaligned pointer or even just creating a misaligned reference is undefined behavior | ||
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| error: aborting due to 2 previous errors | ||
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This is really nice, thank you.
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And it took me only three months since you suggested it...^^
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@bors r+ rollup |
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📌 Commit f511c5e has been approved by |
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| "assignment to non-`Copy` union field") | ||
| "assignment to non-`Copy` union field", | ||
| "the previous content of the field may be dropped, which \ | ||
| cause undefined behavior if the field was not properly \ |
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I must be blind, what is the typo there?
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Oh, it must be "which causes", of course. Sorry!
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I should also add that I am not yet sure why "assignment to non- |
I verified from the RFC that this is exactly what happens. (There is a more elaborate scheme being proposed where fields are only sometimes dropped, but right now it seems to always drop.) |
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Fixed typo. |
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@bors r=estebank |
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@RalfJung: 🔑 Insufficient privileges: Not in reviewers |
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@estebank looks like you have to r+ yourself. |
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@bors r+ |
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📌 Commit f68323b has been approved by |
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improve error message shown for unsafe operations Add a short explanation saying why undefined behavior could arise. In particular, the error many people got for "creating a pointer to a packed field requires unsafe block" was not worded great -- it lead to people just adding the unsafe block without considering if what they are doing follows the rules. I am not sure if a "note" is the right thing, but that was the easiest thing to add... Inspired by @gnzlbg at rust-lang#46043 (comment)
Rollup of 14 pull requests Successful merges: - #51614 (Correct suggestion for println) - #51952 ( hygiene: Decouple transparencies from expansion IDs) - #52193 (step_by: leave time of item skip unspecified) - #52207 (improve error message shown for unsafe operations) - #52223 (Deny bare trait objects in in src/liballoc) - #52224 (Deny bare trait objects in in src/libsyntax) - #52239 (Remove sync::Once::call_once 'static bound) - #52247 (Deny bare trait objects in in src/librustc) - #52248 (Deny bare trait objects in in src/librustc_allocator) - #52252 (Deny bare trait objects in in src/librustc_codegen_llvm) - #52253 (Deny bare trait objects in in src/librustc_data_structures) - #52254 (Deny bare trait objects in in src/librustc_metadata) - #52261 (Deny bare trait objects in in src/libpanic_unwind) - #52265 (Deny bare trait objects in in src/librustc_codegen_utils) Failed merges: r? @ghost
Add a short explanation saying why undefined behavior could arise. In particular, the error many people got for "creating a pointer to a packed field requires unsafe block" was not worded great -- it lead to people just adding the unsafe block without considering if what they are doing follows the rules.
I am not sure if a "note" is the right thing, but that was the easiest thing to add...
Inspired by @gnzlbg at #46043 (comment)