I'm observing some strange behavior and could use some help understanding it.
The specification <https://go.dev/ref/spec#Comparison_operators%E2%80%9D> says: *“Pointers to distinct zero-size variables may or may not be equal.”* With the following program (Go Playground <https://go.dev/play/p/D41jZhecbyK>): var ( a struct{} b struct{} eq = &a == &b ) func f1() { println("&a:", &a) println("&b:", &b) println("&a == &b:", eq) } I'll get &a: 0x537580 &b: 0x537580 &a == &b: false Okay, a and b are empty structs, do not escape, so they share the same address - fine. Also, some optimizer sees that a and b are different variables, so their addresses must be different, and decides to make &a == &b a constant - wrong, but I can live with that. My question would be: Is this behavior expected, somehow defined by the specification, or is it undefined behavior? Let's try to confuse the optimizer a little (Go Playground <https://go.dev/play/p/_r5WEULKPKd>): var ( a struct{} b struct{} aa = &a ba = &b eq = aa == ba ) func f1() { println("&a:", aa) println("&b:", ba) println("&a == &b:", eq) } results in &a: 0x5375a0 &b: 0x5375a0 &a == &b: true Mission accomplished, too complicated to calculate in advance. But globals are bad, so (Go Playground <https://go.dev/play/p/SleVYsVj3u5>): func f2() { var ( a struct{} b struct{} aa = &a ba = &b eq = aa == ba ) println("&a:", aa) println("&b:", ba) println("&a == &b:", eq) } &a: 0xc000046740 &b: 0xc000046740 &a == &b: false Seems like inlining helps generate false answers. The interesting part here is that I can create two pointers (which may or may not be equal per specification), but depending on how I compare them I get different results. -- 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 on the web visit https://groups.google.com/d/msgid/golang-nuts/9dc278ed-d138-4adc-bf68-787bdc8cb71cn%40googlegroups.com.
