Right, most approaches don't cover all the cases (which would be impossible, but we can still try to tend to). In my porous memories, some cases were not exactly about immutability, rather about escape analysis : "If I just built []byte x, and I return string(x), and x doesn't escape, then the conversion shoud be free of charge" and symmetrically though less useful : "If I just built string y, and I return []byte(y), and y doesn't escape, then the conversion shoud be free of charge"
But I don't have skills to answer these kind of compiler-related question, so I would be more comfortable letting others speak. Cheers On Monday, February 13, 2017 at 11:30:21 PM UTC+1, Alex Flint wrote: > > Thanks Val. I actually did a search before posting this and turned up many > of those same links, but it seems like they're all just reasoning from the > immutability of strings, which I don't think is quite sufficient to answer > the question in all cases. Anyway, thanks for your help and I think for now > I'll work on the assumption that string/byteslice conversions do always > copy. > > On Mon, Feb 13, 2017 at 2:22 PM Val <dele...@gmail.com <javascript:>> > wrote: > >> Hello Alex, >> good point. I remember this has indeed come up in discussions in this >> forum. >> >> Searching "byte slice string copy" gave (among others) [1] [2] [3] [4] >> [5] [6] [7]. All of these look related to the suggested optimization "don't >> allocate© for a []byte to string, or string to []byte, conversion, >> under certain circumstances". >> Cheers >> Val >> >> [1] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/m46jaS6bgZg/R5hSOPFz5m0J >> [2] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/CwoKDOhv6vw/sf35VZOZDQAJ >> [3] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/ENgbUzYvCuU/gWa8V8wGAwAJ >> [4] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/ajXzEM6lqJI/vRsqXxizBAAJ >> [5] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/f2cX-BIJsqY/bzK77xpU8PMJ >> [6] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/IfILC-wllaI/U8v88T3aBgAJ >> [7] >> https://groups.google.com/forum/#!searchin/golang-nuts/byte$20slice$20string$20copy|sort:relevance/golang-nuts/fXmG83gZOJg/eixtKSQiNysJ >> >> >> On Monday, February 13, 2017 at 9:31:06 PM UTC+1, Alex Flint wrote: >>> >>> As of go1.8, do conversions between strings and byte slices always >>> generate a copy? >>> >>> I understand the immutability guarantees in the language spec, but I'm >>> interested in this from an efficiency standpoint. I can imagine a compiler >>> that analyzes whether a byte slice created from such a conversion is ever >>> modified and foregoing the copy in some cases, while still adhering to the >>> immutability guarantees. >>> >>> I have searched this forum for a past thread on this topic but have come >>> up empty. Feel free to point me to the relevant discussion. >>> >>> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "golang-nuts" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/golang-nuts/C6BBNTRSEwg/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> golang-nuts...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout. >> > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
