runtime/cgo: replace fprintf(stderr, ...) with fatalf(...) for linux/android

Both stdout and stderr are sent to /dev/null in android
apps. Introducing fatalf allows android to implement its
own copy that sends fatal errors to __android_log_print.

LGTM=minux, dave
R=minux, dave
CC=golang-codereviews
https://golang.org/cl/108400045

src/pkg/runtime/cgo/gcc_android.c

+// Copyright 2014 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 <stdarg.h>
+#include <android/log.h>
+#include "libcgo.h"
+
+void
+fatalf(const char* format, ...)
+{
+	va_list ap;
+
+	// Write to both stderr and logcat.
+	//
+	// When running from an .apk, /dev/stderr and /dev/stdout
+	// redirect to /dev/null. And when running a test binary
+	// via adb shell, it's easy to miss logcat.
+
+	fprintf(stderr, "runtime/cgo: ");
+	va_start(ap, format);
+	vfprintf(stderr, format, ap);
+	va_end(ap);
+	fprintf(stderr, "\n");
+
+	va_start(ap, format);
+	__android_log_vprint(ANDROID_LOG_FATAL, "runtime/cgo", format, ap);
+	va_end(ap);
+
+	abort();
+}

src/pkg/runtime/cgo/gcc_android_arm.c

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-#include <android/log.h>
 #include <pthread.h>
 #include <signal.h>
 #include <stdio.h>
@@ -28,9 +27,7 @@ inittls(void **tlsg, void **tlsbase)
 
 	err = pthread_key_create(&k, nil);
 	if(err != 0) {
-		fprintf(stderr, "runtime/cgo: pthread_key_create failed: %d\n", err);
-		__android_log_print(ANDROID_LOG_FATAL, "runtime/cgo", "pthread_key_create failed: %d", err);
-		abort();
+		fatalf("pthread_key_create failed: %d", err);
 	}
 	pthread_setspecific(k, (void*)magic1);
 	for (i=0; i<PTHREAD_KEYS_MAX; i++) {
@@ -40,9 +37,7 @@ inittls(void **tlsg, void **tlsbase)
 			return;
 		}
 	}
-	fprintf(stderr, "runtime/cgo: could not find pthread key\n");
-	__android_log_print(ANDROID_LOG_FATAL, "runtime/cgo", "could not find pthread key");
-	abort();
+	fatalf("could not find pthread key");
 }
 
 void (*x_cgo_inittls)(void **tlsg, void **tlsbase) = inittls;

src/pkg/runtime/cgo/gcc_fatalf.c

+// Copyright 2014 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.
+
+// +build !android,linux
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "libcgo.h"
+
+void
+fatalf(const char* format, ...)
+{
+	va_list ap;
+
+	fprintf(stderr, "runtime/cgo: ");
+	va_start(ap, format);
+	vfprintf(stderr, format, ap);
+	va_end(ap);
+	fprintf(stderr, "\n");
+	abort();
+}

src/pkg/runtime/cgo/gcc_linux_386.c

@@ -49,8 +49,7 @@ _cgo_sys_thread_start(ThreadStart *ts)
 	pthread_sigmask(SIG_SETMASK, &oset, nil);
 
 	if (err != 0) {
-		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
-		abort();
+		fatalf("pthread_create failed: %s", strerror(err));
 	}
 }
 

src/pkg/runtime/cgo/gcc_linux_amd64.c

@@ -44,8 +44,7 @@ _cgo_sys_thread_start(ThreadStart *ts)
 	pthread_sigmask(SIG_SETMASK, &oset, nil);
 
 	if (err != 0) {
-		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
-		abort();
+		fatalf("pthread_create failed: %s", strerror(err));
 	}
 }
 

src/pkg/runtime/cgo/gcc_linux_arm.c

@@ -9,6 +9,7 @@
 
 static void *threadentry(void*);
 
+void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
 void (*setg_gcc)(void*);
 
 void
@@ -36,8 +37,7 @@ _cgo_sys_thread_start(ThreadStart *ts)
 	pthread_sigmask(SIG_SETMASK, &oset, nil);
 
 	if (err != 0) {
-		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
-		abort();
+		fatalf("pthread_create failed: %s", strerror(err));
 	}
 }
 
@@ -62,8 +62,6 @@ threadentry(void *v)
 	return nil;
 }
 
-void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
-
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {

src/pkg/runtime/cgo/libcgo.h

@@ -58,3 +58,8 @@ void crosscall_amd64(void (*fn)(void));
  * Call fn in the 8c world.
  */
 void crosscall_386(void (*fn)(void));
+
+/*
+ * Prints error then calls abort. For linux and android.
+ */
+void fatalf(const char* format, ...);