runtime: Will the variable pointer in Go side be invalid during calling C function due to garbage collection?

[shinningstar]

Go garbage collector does not know Go variable(pointer) used in C world. In Go package source code:
https://github.com/golang/go/blob/master/src/net/cgo_unix.go#L47 here is a variable "hints" in Go world which is passed into C function getaddrinfo(). Theoretically, is it possible that the address of "hints" is invalid due to Go garbage collection?

[ianlancetaylor]

Pointers passed to C by cgo are live until the end of the cgo call. I don't think this needs to be documented as such, at least not until we actually resolve #8310.

The general cgo problem was raised in issue #10303 and fixed in http://golang.org/cl/10814.

[shinningstar]

@ianlancetaylor From the discussion of #10303 , it seems that the pointer passed to C function does not escape until the fix in http://golang.org/cl/10814. So the problem I mentioned may be a real problem in current released 1.4.1/1.4.2. Is that true?

[ianlancetaylor]

The 1.4.x and earlier releases are fine. In those releases, cgo generated C code, and pointers passed to C code always escape. Issue #10303 was reported against tip, after cgo had been changed to generate Go code. The fix was to cause the compiler to treat pointers as always escaping, which is exactly what it did in 1.4 and earlier releases.