Comment 1:

the C compiler will eventually go away. Plan for that, so
don't rely on it.
Note the Plan 9 C compiler isn't fully ANSI compliant,
and we're not going to fix bugs in it (because we control
both the compiler and its input, we will just workaround
its bugs).

Status changed to Unfortunate.

Comment 2:

http://stackoverflow.com/questions/25048775/am-i-doing-something-wrong-or-is-this-a-bug-in-gos-c-compiler/25049681#25049681
Changing the C function signature to `void ·XXH32_test(const unsigned char* input, U32
len, U32 seed, U32 *ret)` and assigning the hash to *ret seems to return the right value.
I still think this is a bug.

Comment 3:

Will the assembler remain?

Comment 4:

Yes, 6a will remain. And it will be written in Go too.
The ultimate goal for 6a is that it will be based on latest
intel manuals, so it will support all the latest instructions.
Anyway, for xxHash, I suggest you'd better write it in Go.
The first reason is that the Plan 9 C Compiler will go away
eventually, and 2nd is that 6g will become better over time,
but we definitely won't spend time to improve 6c.

Comment 5:

R3 #2,
6c and 6g are using different function call ABI in that
go can't read return value from C functions. This is not
a bug (C doesn't support multiple return values.)
you need to do this:
#define FLUSH(x) USED(x)
void ·XXH32_test(const unsigned char* input, U32 len, U32 seed, U32 ret) {
    // calculate ret
    ret = 42;
    FLUSH(&ret);
}
but still, use pure Go is much better.