cc @ianlancetaylor

That's a fairly specific request. It's not a goal of cgo to provide a full set of C string manipulation functions. If I understand correctly, you can do what you want with

C.GoStringN(p, C.strnlen(p, N))

I don't think we need an additional function for this specific use.

With @ianlancetaylor showing the simple way to deal with this, I agree that no additional function is needed. My concern can be dealt with with a documentation note telling people to do this for copying such struct fields instead of just using C.GoString() (and not necessarily in cmd/cgo's godoc; there's the wiki and other supplementary materials on cgo).

(If left alone with no guidance I think that many people will just use C.GoString(), especially if they are not experienced C programmers but are instead just using cgo to connect Go to some C library or the like. Even relatively experienced C programmers sometimes commit this mistake in C code, after all, and it slipped my mind recently when I was writing cgo code. Treating struct fields as C strings is easy and really tempting and it works almost all of the time.)

It is a bad API. But it's unfortunately a common one, either explicitly (you're told that this is the case) or implicitly (some struct has a char field[N] field and documentation doesn't say it's always null-terminated). People creating certain sorts of C APIs love embedded fixed-size char fields instead of out of line char * pointers because it requires less allocation and simplifies things like moving these structs across user space/kernel boundaries. And then people writing Go packages to interface with these C APIs get to deal with the mess.