[build] Support libgo on Solaris 2

[Ian Lance Taylor]

> From: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
> Date: Mon, 10 Jan 2011 16:23:05 +0100

> 	* runtime/go-go.c (__go_go) [!LINKER_SUPPORTS_SPLIT_STACK &&
> 	__sun__ && __svr4__]: Reduce default thread stack size.

> diff -r 72fce0443d71 libgo/runtime/go-go.c
> --- a/libgo/runtime/go-go.c	Sat Jan 08 12:30:04 2011 +0100
> +++ b/libgo/runtime/go-go.c	Sun Jan 09 12:31:06 2011 +0100
> @@ -196,7 +196,21 @@
>  #endif
>    i = pthread_attr_setstacksize (&attr, PTHREAD_STACK_MIN);
>    __go_assert (i == 0);
> +
> +#else /* !LINKER_SUPPORTS_SPLIT_STACK */
> +
> +#if defined __sun__ && defined __svr4__
> +  /* Reduce the thread stack size from the Solaris 2 default of 1 MB
> +     (32-bit) or 2 MB (64-bit) to allow go.test/test/chan/goroutines.go to
> +     work.  The value is just a guess.  */
> +#ifndef PTHREAD_STACK_MIN
> +#define PTHREAD_STACK_MIN (128*1024)
>  #endif
> +  i = pthread_attr_setstacksize (&attr, PTHREAD_STACK_MIN);
> +  __go_assert (i == 0);
> +#endif /* __sun__ && __svr4__ */
> +
> +#endif /* !LINKER_SUPPORTS_SPLIT_STACK */

I don't think this is the way to go.  What this does is reduce the
default stack size of a thread in order to permit more threads to run.
But the effect will be that more threads will overrun their stacks and
crash.  I think it's more likely that a thread will need a lot of stack
than it is that a Go program will need a lot of goroutines.  The
goroutines.go test creates 10000 goroutines.  It should work, of course,
but I don't think we should make it work by sacrificing the size of the
stack for ordinary goroutines.  We should instead let goroutines.go fail
until split stack is implemented.

Ian