alt Hacker NewsThanks for pointing to this. I'm surprised the specification verbiage differs so much between the two standards. However I think the language for C is aspirational and there are cases where compiler optimizations will fail this.
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Georgelemental • today at 4:39 PM
Some of those cases have been fixed. For example, Clang used to reorder UB around volatile loads, but the latest version no longer does so.
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There are a few rare cases where compiler optimization will fail this in GCC. There are also cases where the C spec has defined behavior that optimizers break. Where I know about them, I file bugs. It would be up for users to insist that those get fixed. This includes optimization issues that affect Rust as well.