runtime: put tracebackctxt C functions in .c file

Since tracebackctxt.go uses //export functions, the C functions can't be
externally visible in the C comment. The code was using attributes to
work around that, but that failed on Windows.

Change-Id: If4449fd8209a8998b4f6855ea89e5db1471b2981
Reviewed-on: https://go-review.googlesource.com/22786Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/crash_cgo_test.go

@@ -225,9 +225,6 @@ func TestCgoCrashTraceback(t *testing.T) {
 }
 
 func TestCgoTracebackContext(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skipf("test does not work on %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
 	got := runTestProg(t, "testprogcgo", "TracebackContext")
 	want := "OK\n"
 	if got != want {

src/runtime/testdata/testprogcgo/tracebackctxt.go

@@ -4,103 +4,19 @@
 
 // The __attribute__((weak)) used below doesn't seem to work on Windows.
 
-// +build !windows
-
 package main
 
 // Test the context argument to SetCgoTraceback.
 // Use fake context, traceback, and symbolizer functions.
 
 /*
-#include <stdlib.h>
-#include <stdint.h>
-
-// Use weak declarations so that we can define functions here even
-// though we use //export in the Go code.
-extern void tcContext(void*) __attribute__((weak));
-extern void tcTraceback(void*) __attribute__((weak));
-extern void tcSymbolizer(void*) __attribute__((weak));
-
-extern void G1(void);
-extern void G2(void);
-
-static void C1() {
-	G1();
-}
-
-static void C2() {
-	G2();
-}
-
-struct cgoContextArg {
-	uintptr_t context;
-};
-
-struct cgoTracebackArg {
-	uintptr_t  context;
-	uintptr_t* buf;
-	uintptr_t  max;
-};
-
-struct cgoSymbolizerArg {
-	uintptr_t   pc;
-	const char* file;
-	uintptr_t   lineno;
-	const char* func;
-	uintptr_t   entry;
-	uintptr_t   more;
-	uintptr_t   data;
-};
-
-// Global so that there is only one, weak so that //export works.
-// Uses atomic adds and subtracts to catch the possibility of
-// erroneous calls from multiple threads; that should be impossible in
-// this test case, but we check just in case.
-int contextCount __attribute__((weak));
-
-static int getContextCount() {
-	return __sync_add_and_fetch(&contextCount, 0);
-}
-
-void tcContext(void* parg) {
-	struct cgoContextArg* arg = (struct cgoContextArg*)(parg);
-	if (arg->context == 0) {
-		arg->context = __sync_add_and_fetch(&contextCount, 1);
-	} else {
-		if (arg->context != __sync_add_and_fetch(&contextCount, 0)) {
-			abort();
-		}
-		__sync_sub_and_fetch(&contextCount, 1);
-	}
-}
-
-void tcTraceback(void* parg) {
-	int base, i;
-	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
-	if (arg->context == 0) {
-		// This shouldn't happen in this program.
-		abort();
-	}
-	// Return a variable number of PC values.
-	base = arg->context << 8;
-	for (i = 0; i < arg->context; i++) {
-		if (i < arg->max) {
-			arg->buf[i] = base + i;
-		}
-	}
-}
-
-void tcSymbolizer(void *parg) {
-	struct cgoSymbolizerArg* arg = (struct cgoSymbolizerArg*)(parg);
-	if (arg->pc == 0) {
-		return;
-	}
-	// Report two lines per PC returned by traceback, to test more handling.
-	arg->more = arg->file == NULL;
-	arg->file = "tracebackctxt.go";
-	arg->func = "cFunction";
-	arg->lineno = arg->pc + (arg->more << 16);
-}
+// Defined in tracebackctxt_c.c.
+extern void C1(void);
+extern void C2(void);
+extern void tcContext(void*);
+extern void tcTraceback(void*);
+extern void tcSymbolizer(void*);
+extern int getContextCount(void);
 */
 import "C"
 

src/runtime/testdata/testprogcgo/tracebackctxt_c.c

+// Copyright 2016 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.
+
+// The C definitions for tracebackctxt.go. That file uses //export so
+// it can't put function definitions in the "C" import comment.
+
+#include <stdlib.h>
+#include <stdint.h>
+
+// Functions exported from Go.
+extern void G1(void);
+extern void G2(void);
+
+void C1() {
+	G1();
+}
+
+void C2() {
+	G2();
+}
+
+struct cgoContextArg {
+	uintptr_t context;
+};
+
+struct cgoTracebackArg {
+	uintptr_t  context;
+	uintptr_t* buf;
+	uintptr_t  max;
+};
+
+struct cgoSymbolizerArg {
+	uintptr_t   pc;
+	const char* file;
+	uintptr_t   lineno;
+	const char* func;
+	uintptr_t   entry;
+	uintptr_t   more;
+	uintptr_t   data;
+};
+
+// Uses atomic adds and subtracts to catch the possibility of
+// erroneous calls from multiple threads; that should be impossible in
+// this test case, but we check just in case.
+static int contextCount;
+
+int getContextCount() {
+	return __sync_add_and_fetch(&contextCount, 0);
+}
+
+void tcContext(void* parg) {
+	struct cgoContextArg* arg = (struct cgoContextArg*)(parg);
+	if (arg->context == 0) {
+		arg->context = __sync_add_and_fetch(&contextCount, 1);
+	} else {
+		if (arg->context != __sync_add_and_fetch(&contextCount, 0)) {
+			abort();
+		}
+		__sync_sub_and_fetch(&contextCount, 1);
+	}
+}
+
+void tcTraceback(void* parg) {
+	int base, i;
+	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
+	if (arg->context == 0) {
+		// This shouldn't happen in this program.
+		abort();
+	}
+	// Return a variable number of PC values.
+	base = arg->context << 8;
+	for (i = 0; i < arg->context; i++) {
+		if (i < arg->max) {
+			arg->buf[i] = base + i;
+		}
+	}
+}
+
+void tcSymbolizer(void *parg) {
+	struct cgoSymbolizerArg* arg = (struct cgoSymbolizerArg*)(parg);
+	if (arg->pc == 0) {
+		return;
+	}
+	// Report two lines per PC returned by traceback, to test more handling.
+	arg->more = arg->file == NULL;
+	arg->file = "tracebackctxt.go";
+	arg->func = "cFunction";
+	arg->lineno = arg->pc + (arg->more << 16);
+}