src/runtime/cgo/gcc_darwin_amd64.c

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include <string.h> /* for strerror */
#include <pthread.h>
#include <signal.h>
#include "libcgo.h"
#include "libcgo_unix.h"

static void* threadentry(void*);

void
x_cgo_init(G *g)
{
	pthread_attr_t attr;
	size_t size;

	pthread_attr_init(&attr);
	pthread_attr_getstacksize(&attr, &size);
	g->stacklo = (uintptr)&attr - size + 4096;
	pthread_attr_destroy(&attr);
}


void
_cgo_sys_thread_start(ThreadStart *ts)
{
	pthread_attr_t attr;
	sigset_t ign, oset;
	pthread_t p;
	size_t size;
	int err;

	sigfillset(&ign);
	pthread_sigmask(SIG_SETMASK, &ign, &oset);

	pthread_attr_init(&attr);
	pthread_attr_getstacksize(&attr, &size);
	// Leave stacklo=0 and set stackhi=size; mstart will do the rest.
	ts->g->stackhi = size;
	err = _cgo_try_pthread_create(&p, &attr, threadentry, ts);

	pthread_sigmask(SIG_SETMASK, &oset, nil);

	if (err != 0) {
		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
		abort();
	}
}

static void*
threadentry(void *v)
{
	ThreadStart ts;

	ts = *(ThreadStart*)v;
	free(v);

	// Move the g pointer into the slot reserved in thread local storage.
	// Constant must match the one in cmd/link/internal/ld/sym.go.
	asm volatile("movq %0, %%gs:0x30" :: "r"(ts.g));

	crosscall_amd64(ts.fn);
	return nil;
}