Looking through that file, I didn't see a single goto (but I could have missed one) that didn't go to one of: unlock_out, out, or error. I don't think there would be any diminishment of runtime efficiency if you dropped the goto statements, and it may actually improve performance to drop them since they correspond to a jump that could be removed from each of their occurrences. Though it would also increase the code size (everything in that section of code has to be replicated), so that could be an issue. Tradeoffs, would have to be measured to know for sure.
However, they do improve the maintainability of the code. I find it interesting, looking at them and having done a quick reread of Knuth's take on goto statements (for another comment I made here) that these uses correspond to what other languages possess as syntactic elements in the structured programming vein, which is one of the things he discusses in favor of both structured programming and goto statements. In favor of structured programming, you get new syntactic elements that provide useful semantics that make the code clearer. Why are we doing this jump? Oh, it's a conditional (if/then/else) or a loop (for, while). But when you lack the syntax and semantics for that, the goto statement can fill in the gaps (when used carefully, deliberately).
Specifically, out mostly corresponds to defer (in Go) or finally in other languages. error is like try/catch/finally in Java and others. unlock_out would be like the with statements you get in some other languages.
EDIT: Reexamined this specific source file. Most of the out sections are 0-2 statements in addition to the return. So in the 0 case, there ought to be a performance improvement by just returning, though I imagine a compiler can optimize the goto's away. In the 1-2 statement range it'd be a tossup on whether the increase in function size would cost more (cache miss and similar) than the indirection itself costs. I only saw one (it's a large file, I didn't look too closely) that had a larger out section than 2 statements, and that one had enough that the indirection is probably worth the performance cost.
But, in all cases (except the 0-statement case) it still is better from a maintainability perspective, whether or not it helps performance. In the 0-statement case, I wonder if they're vestigial. If there were other statements included that were dropped for some reason. But I'm not going to dig further into this because now it's time for me to study.
However, they do improve the maintainability of the code. I find it interesting, looking at them and having done a quick reread of Knuth's take on goto statements (for another comment I made here) that these uses correspond to what other languages possess as syntactic elements in the structured programming vein, which is one of the things he discusses in favor of both structured programming and goto statements. In favor of structured programming, you get new syntactic elements that provide useful semantics that make the code clearer. Why are we doing this jump? Oh, it's a conditional (if/then/else) or a loop (for, while). But when you lack the syntax and semantics for that, the goto statement can fill in the gaps (when used carefully, deliberately).
Specifically, out mostly corresponds to defer (in Go) or finally in other languages. error is like try/catch/finally in Java and others. unlock_out would be like the with statements you get in some other languages.
EDIT: Reexamined this specific source file. Most of the out sections are 0-2 statements in addition to the return. So in the 0 case, there ought to be a performance improvement by just returning, though I imagine a compiler can optimize the goto's away. In the 1-2 statement range it'd be a tossup on whether the increase in function size would cost more (cache miss and similar) than the indirection itself costs. I only saw one (it's a large file, I didn't look too closely) that had a larger out section than 2 statements, and that one had enough that the indirection is probably worth the performance cost.
But, in all cases (except the 0-statement case) it still is better from a maintainability perspective, whether or not it helps performance. In the 0-statement case, I wonder if they're vestigial. If there were other statements included that were dropped for some reason. But I'm not going to dig further into this because now it's time for me to study.