Re: [9fans] Go: CGO and Plan 9

[Anthony Martin <ality@pbrane.org>]

Aram Hăvărneanu <aram.h@mgk.ro> once said:
> ?c and ?g use the same calling convention, and segmented stacks are
> implemented by the linker. You don't need cgo in order to call C code
> from Go. Why do you want cgo?

This isn't true. Most of the Plan 9 compilers will pass the
first function argument in a register (not including 8c) and
return the result in a register (including 8c).

The C compilers in the Go toolchain pass everything on the
stack and return the result in a register.

The Go compilers pass everything on the stack including the
output parameters. No registers are involved in the calling
convention.

Another difference is in C is variadic functions in the face
of segmented stacks. The C compilers in the Go toolchain will
not compile a variadic function without a NOSPLIT annotation.
And even then, only if the resulting stack frame is small.

> Look at the various C files in the Go standard library, especially
> inside runtime. Those are compiled with the Plan 9 compiler and Go
> calls it just fine.

They're also careful not to validate the above assumptions
and they do not include any outside header files.

The right way to solve this problem is to modify cgo. I just
haven't had the time.

Cheers,
  Anthony