Ub vs tbd #10
Ub vs tbd #10
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There is an issue open in the UCG repo about defining these types of behavior that maybe we should pursue more actively there (rust-lang/unsafe-code-guidelines#201 rust-lang/unsafe-code-guidelines#202). I think that in the meantime, it's fine to add things here, but we should update this to point there as things achieve consensus (for UB, this already happened).
| * Examples: | ||
| * Details of how a Rust panic presents itself in "C unwind" ABI on msvc | ||
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| ## TBD as an "project-local planning measure" |
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| ## TBD as an "project-local planning measure" | |
| ## TBD as a "project-local planning measure" |
| * We *may* specify this at some point in the future, but there are no plans to do so. | ||
| * Example: Rust ABI compatibility | ||
| * Example: What symbols get exported by a DLL | ||
| * We wish to specify this behavior in the near future, as part of the FFI-unwind project |
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Bullet-point hierarchy doesn't match the heading, "three categories"... I also feel that most of this section feels redundant with the terminology page.
| This directory stores "resolved concerns" -- basically, whenever there | ||
| is a non-obvious tradeoff, we try to create a document that describes | ||
| the tradeoff in full, and then documents the resolution we ultimately | ||
| reached. Sometimes these documents include dissents, if not everyone |
| Rust evolves. Eventually, though, we do intend to define many (but not | ||
| all) aspects of how Rust panics and native unwinding interoperate. | ||
| Moreover, we guarantee that unwinding will **not** result in | ||
| [Undefined Behavior] and in particular not [LLVM-UB]. |
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This is more of an idea for the future, but maybe we should use a term like "optimizer-UB" or "intermediate-representation-UB" instead of LLVM-UB. The core idea of the term, I think, is that we are avoiding the form of UB that lets compilers make "adversarial" optimizations (in particular, in our case, eliminating landing pads).
| e.g. [rust-lang/rust#28728]). The main reason it is worth separating | ||
| LLVM-UB from the more general form of Rust UB is that, while both | ||
| forms of UB can cause arbitrary things to happen in your | ||
| code. However, as a practical measure, LLVM-UB is much more *likely |
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Looks like these sentences are really supposed to be one sentence that was inadvertently split.
| code. However, as a practical measure, LLVM-UB is much more *likely | |
| code, LLVM-UB is much more *likely* to do so in practice. |
(Can't submit a multi-line suggestion yet, but of course this would mean deleting the next line 😄 )
| We use the term "unspecified behavior" to refer to behavior that may | ||
| vary across Rust releases, depending on what options are given to the | ||
| compiler, or even -- in extreme cases -- across executions of the Rust | ||
| compiler. However, unlike undefined behavior, the resulting execution |
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It may be worth noting variation across platforms, too.
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