runtime/cgo: merge bodies of cgo_sys_thread_start on windows

The bodies of cgo_sys_thread_start (and x_cgo_sys_thread_create) are
nearly identical on all of the windows ports.

Create a single _cgo_beginthread implementation that contains the body
and is used on all ports. This will reduce churn in an upcoming CL to
add retry logic.

We could theoretically have a single implementation of
_cgo_sys_thread_start shared by all ports, but I keep them separate for
ease of searching. Right now every single port implements this function
in their gcc_GOOS_GOARCH.c file, so it is nice to keep this symmetry.

_cgo_dummy_export must move out of libcgo_windows.h because it is a
definition and the inclusion of libcgo_windows.h in multiple files
creates duplicate definitions.

For #52572.

Change-Id: I9fa22009389349c754210274c7db2631b061f9c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/410354
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/cgo/gcc_libinit_windows.c

@@ -13,6 +13,16 @@
 #include <errno.h>
 
 #include "libcgo.h"
+#include "libcgo_windows.h"
+
+// Ensure there's one symbol marked __declspec(dllexport).
+// If there are no exported symbols, the unfortunate behavior of
+// the binutils linker is to also strip the relocations table,
+// resulting in non-PIE binary. The other option is the
+// --export-all-symbols flag, but we don't need to export all symbols
+// and this may overflow the export table (#40795).
+// See https://sourceware.org/bugzilla/show_bug.cgi?id=19011
+__declspec(dllexport) int _cgo_dummy_export;
 
 static volatile LONG runtime_init_once_gate = 0;
 static volatile LONG runtime_init_once_done = 0;
@@ -53,13 +63,7 @@ _cgo_maybe_run_preinit() {
 
 void
 x_cgo_sys_thread_create(void (*func)(void*), void* arg) {
-	uintptr_t thandle;
+	_cgo_beginthread(func, arg);
-
-	thandle = _beginthread(func, 0, arg);
-	if(thandle == -1) {
-		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
-		abort();
-	}
 }
 
 int
@@ -123,3 +127,13 @@ void (*(_cgo_get_context_function(void)))(struct context_arg*) {
 	LeaveCriticalSection(&runtime_init_cs);
 	return ret;
 }
+
+void _cgo_beginthread(void (*func)(void*), void* arg) {
+	uintptr_t thandle;
+
+	thandle = _beginthread(func, 0, arg);
+	if (thandle == -1) {
+		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
+		abort();
+	}
+}

src/runtime/cgo/gcc_windows_386.c

@@ -22,13 +22,7 @@ x_cgo_init(G *g)
 void
 _cgo_sys_thread_start(ThreadStart *ts)
 {
-	uintptr_t thandle;
+	_cgo_beginthread(threadentry, ts);
-
-	thandle = _beginthread(threadentry, 0, ts);
-	if(thandle == -1) {
-		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
-		abort();
-	}
 }
 
 static void

src/runtime/cgo/gcc_windows_amd64.c

@@ -24,13 +24,7 @@ x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 void
 _cgo_sys_thread_start(ThreadStart *ts)
 {
-	uintptr_t thandle;
+	_cgo_beginthread(threadentry, ts);
-
-	thandle = _beginthread(threadentry, 0, ts);
-	if(thandle == -1) {
-		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
-		abort();
-	}
 }
 
 static void

src/runtime/cgo/gcc_windows_arm64.c

@@ -23,13 +23,7 @@ x_cgo_init(G *g, void (*setg)(void*))
 void
 _cgo_sys_thread_start(ThreadStart *ts)
 {
-	uintptr_t thandle;
+	_cgo_beginthread(threadentry, ts);
-
-	thandle = _beginthread(threadentry, 0, ts);
-	if(thandle == -1) {
-		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
-		abort();
-	}
 }
 
 extern void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g);

src/runtime/cgo/libcgo_windows.h

@@ -2,11 +2,5 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Ensure there's one symbol marked __declspec(dllexport).
+// Call _beginthread, aborting on failure.
-// If there are no exported symbols, the unfortunate behavior of
+void _cgo_beginthread(void (*func)(void*), void* arg);
-// the binutils linker is to also strip the relocations table,
-// resulting in non-PIE binary. The other option is the
-// --export-all-symbols flag, but we don't need to export all symbols
-// and this may overflow the export table (#40795).
-// See https://sourceware.org/bugzilla/show_bug.cgi?id=19011
-__declspec(dllexport) int _cgo_dummy_export;