runtime/cgo: use CreateThread instead of _beginthread

_beginthread is intended to be used together with the C runtime.
The cgo runtime doesn't use it, so better use CreateThread directly,
which is the Windows API for creating threads.

Cq-Include-Trybots: luci.golang.try:gotip-windows-amd64-longtest,gotip-windows-arm64
Change-Id: Ic6cf75f69f62a3babf5e74155da1aac70961886c
Reviewed-on: https://go-review.googlesource.com/c/go/+/651995
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/cgo/gcc_libinit_windows.c

@@ -2,19 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-# ifdef __CYGWIN__
+#ifdef __CYGWIN__
 #error "don't use the cygwin compiler to build native Windows programs; use MinGW instead"
-#else
-// Exclude the following code from Cygwin builds.
-// Cygwin doesn't implement process.h nor does it support _beginthread.
+#endif
 
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
-#include <process.h>
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <errno.h>
 
 #include "libcgo.h"
 #include "libcgo_windows.h"
@@ -69,7 +65,7 @@ _cgo_maybe_run_preinit() {
 }
 
 void
-x_cgo_sys_thread_create(void (*func)(void*), void* arg) {
+x_cgo_sys_thread_create(unsigned long (__stdcall *func)(void*), void* arg) {
 	_cgo_beginthread(func, arg);
 }
 
@@ -141,26 +137,25 @@ void (*(_cgo_get_context_function(void)))(struct context_arg*) {
 	return ret;
 }
 
-void _cgo_beginthread(void (*func)(void*), void* arg) {
+void _cgo_beginthread(unsigned long (__stdcall *func)(void*), void* arg) {
 	int tries;
-	uintptr_t thandle;
+	HANDLE thandle;
 
 	for (tries = 0; tries < 20; tries++) {
-		thandle = _beginthread(func, 0, arg);
-		if (thandle == -1 && errno == EACCES) {
+		thandle = CreateThread(NULL, 0, func, arg, 0, NULL);
+		if (thandle == 0 && GetLastError() == ERROR_NOT_ENOUGH_MEMORY) {
 			// "Insufficient resources", try again in a bit.
 			//
 			// Note that the first Sleep(0) is a yield.
 			Sleep(tries); // milliseconds
 			continue;
-		} else if (thandle == -1) {
+		} else if (thandle == 0) {
 			break;
 		}
+		CloseHandle(thandle);
 		return; // Success!
 	}
 
-	fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
+	fprintf(stderr, "runtime: failed to create new OS thread (%lu)\n", GetLastError());
 	abort();
 }
-
-#endif // __CYGWIN__

src/runtime/cgo/gcc_windows_386.c

@@ -11,7 +11,7 @@
 #include "libcgo.h"
 #include "libcgo_windows.h"
 
-static void threadentry(void*);
+static unsigned long __stdcall threadentry(void*);
 static void (*setg_gcc)(void*);
 static DWORD *tls_g;
 
@@ -29,7 +29,8 @@ _cgo_sys_thread_start(ThreadStart *ts)
 }
 
 extern void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g);
-static void
+static unsigned long
+__stdcall
 threadentry(void *v)
 {
 	ThreadStart ts;
@@ -50,4 +51,5 @@ threadentry(void *v)
 	);
 
 	crosscall1(ts.fn, setg_gcc, ts.g);
+	return 0;
 }

src/runtime/cgo/gcc_windows_amd64.c

@@ -11,7 +11,7 @@
 #include "libcgo.h"
 #include "libcgo_windows.h"
 
-static void threadentry(void*);
+static unsigned long __stdcall threadentry(void*);
 static void (*setg_gcc)(void*);
 static DWORD *tls_g;
 
@@ -30,7 +30,8 @@ _cgo_sys_thread_start(ThreadStart *ts)
 }
 
 extern void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g);
-static void
+static unsigned long
+__stdcall
 threadentry(void *v)
 {
 	ThreadStart ts;
@@ -49,4 +50,5 @@ threadentry(void *v)
 	);
 
 	crosscall1(ts.fn, setg_gcc, (void*)ts.g);
+	return 0;
 }

src/runtime/cgo/gcc_windows_arm64.c

@@ -11,7 +11,7 @@
 #include "libcgo.h"
 #include "libcgo_windows.h"
 
-static void threadentry(void*);
+static unsigned long __stdcall threadentry(void*);
 static void (*setg_gcc)(void*);
 
 void
@@ -28,7 +28,8 @@ _cgo_sys_thread_start(ThreadStart *ts)
 
 extern void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g);
 
-static void
+static unsigned long
+__stdcall
 threadentry(void *v)
 {
 	ThreadStart ts;
@@ -37,4 +38,5 @@ threadentry(void *v)
 	free(v);
 
 	crosscall1(ts.fn, setg_gcc, (void *)ts.g);
+	return 0;
 }

src/runtime/cgo/libcgo_windows.h

@@ -3,4 +3,4 @@
 // license that can be found in the LICENSE file.
 
 // Call _beginthread, aborting on failure.
-void _cgo_beginthread(void (*func)(void*), void* arg);
+void _cgo_beginthread(unsigned long (__stdcall *func)(void*), void* arg);