s/fmt.String/fmt.Sprintf/ On Thursday, September 1, 2016 at 12:25:24 PM UTC+3, dja...@gmail.com wrote: > > Hi, > Do you know what infinite recursion is ? > fmt.String use your String method > > see https://play.golang.org/p/jeOilZW7JU > > > On Thursday, September 1, 2016 at 11:59:12 AM UTC+3, Muhammad Shulhan > wrote: >> >> Dear all, >> >> I will describe the problem step by step, please bear with me. >> >> Lets take a look at first example , >> >> package main >>> >>> import ( >>> "fmt" >>> ) >>> >>> type Slices []string >>> >>> func (sl *Slices) String() string { >>> // OK >>> return fmt.Sprint(sl) >>> } >>> >>> func main() { >>> var slices Slices >>> >>> fmt.Print("slices:", slices) >>> } >>> >> >> >> Run: https://play.golang.org/p/Cjb0xCVaCC >> Output: >> >> slices:[] >>> >> >> Let change String() return to fmt.Sprint(*sl). >> >> Run: https://play.golang.org/p/St6TyltA56 >> Output: >> >> slices:[] >>> >> >> Using the above prototype lets build a flag that parse Slices. Here is the >> code that return without stack overflow, >> >> package main >>> >>> import ( >>> "flag" >>> "fmt" >>> ) >>> >>> type Slices []string >>> >>> func (sl *Slices) String() string { >>> return fmt.Sprint(*sl) >>> } >>> >>> func (sl *Slices) Set(vv string) error { >>> // STUB for clarity >>> return nil >>> } >>> >>> func main() { >>> var sl Slices >>> flag.Var(&sl, "slices", "Test parsing slice flag.") >>> flag.Parse() >>> >>> fmt.Printf("slices: %s\n", sl) >>> } >> >> >> Run: https://play.golang.org/p/Sol4C8hRk7 >> Output: >> >> slices: [] >>> >> >> Last one, lets change the String return to "fmt.Sprint(sl)". >> >> Run: https://play.golang.org/p/550Krvim77 >> Output: >> >> runtime: goroutine stack exceeds 250000000-byte limit >>> >> fatal error: stack overflow >>> >> >> Question: is this a bug? If it is I would report one. >> >> PS: >> >> Previous discussion that I found mentioning the same problem: >> >> * >> https://groups.google.com/forum/#!searchin/golang-nuts/fmt.Sprint|sort:relevance/golang-nuts/jJ72z0Ssahc/FDwArwNCiw4J >> >
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