Thanks Ian and Dominik for the tips. I have checked the issue 72860 and found randall77 posted a comment that I couldn't confirm from golang spec(go.dev/ref/spec):
//https://github.com/golang/go/issues/72860#issuecomment-2734549770 ``` Where f returns a pointer and an error. f expects its callers to only use the ptr result if the error is nil. And in particular, f returns a nil pointer whenever it returns a non-nil error. This code is incorrect, in that it dereferences the ptr result before checking the error. The Go spec says that it should nil pointer panic if f returns a nil pointer and non-nil error. ``` I did a search in whole spec and did't find any descriptions about it. >From my understanding, `v, err := f()` is like `v1, v2 := f()` from compiler's view, checking error is user code's business logic and couldn't be assumed by compiler. If it's defined in spec, what about variants like `a, b, err := f()` or `a, b, err1, err2 := f()`？ Ge 在2025年7月6日星期日 UTC+8 07:52:56<Dominik Honnef (dominikh)> 写道： > Memory beats git bisect, but this was indeed fixed by > a1ddbdd3ef8b739aab53f20d6ed0a61c3474cf12. > > On Saturday, July 5, 2025 at 6:36:57 PM UTC+2 Ian Lance Taylor wrote: > >> On Sat, Jul 5, 2025 at 8:24 AM Ge <everg...@gmail.com> wrote: >> > >> > As follows showing, when `-N` is enabled with compiler, it gives the >> expected output. >> > ``` >> > ➜ grd more nf2.go >> > package main >> > >> > import "os" >> > >> > func main() { >> > f, err := os.Open("nonExistFile") >> > fname := f.Name() >> > if err != nil { >> > println("failed to open file, Error:", err.Error()) >> > return >> > } >> > >> > println("filename:", fname) >> > } >> > ➜ grd go run nf2.go >> > failed to open file, Error: open nonExistFile: no such file or >> directory >> > >> > ➜ grd go run -gcflags="-N" nf2.go >> > panic: runtime error: invalid memory address or nil pointer dereference >> > [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4782e3] >> > >> > goroutine 1 [running]: >> > os.(*File).Name(...) >> > /usr/local/go/src/os/file.go:62 >> > main.main() >> > /root/grd/nf2.go:7 +0x123 >> > exit status 2 >> > >> > ➜ grd go version >> > go version go1.24.4 linux/amd64 >> > ``` >> >> This may be https://go.dev/issue/72860. In any case, it works >> correctly (that is, it panics) on HEAD and the upcoming Go 1.25 >> release. >> >> Ian >> > -- 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. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/4dc50973-96ca-4a6f-aabc-ac0352375f37n%40googlegroups.com.
