From 0f395b7ba056ccec3915737cfece81ca2161e980 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Tue, 8 Oct 2013 13:19:00 -0700
Subject: [PATCH] Make logging fall back to /dev/stderr if we're on the host.

Otherwise you get no logging, which sucks.

Change-Id: Iea1e8f996461afbb217a55711b7967005c39cfcb
---
 libc/bionic/libc_logging.cpp | 25 +++++++++++++++++++++++++
 linker/linker_debug.h        |  5 -----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/libc/bionic/libc_logging.cpp b/libc/bionic/libc_logging.cpp
index 6bf7415d7..635f8d11a 100644
--- a/libc/bionic/libc_logging.cpp
+++ b/libc/bionic/libc_logging.cpp
@@ -419,9 +419,34 @@ int __libc_format_fd(int fd, const char* format, ...) {
   return os.total;
 }
 
+static int __libc_write_stderr(const char* tag, const char* msg) {
+  int fd = TEMP_FAILURE_RETRY(open("/dev/stderr", O_CLOEXEC | O_WRONLY));
+  if (fd == -1) {
+    return -1;
+  }
+
+  iovec vec[4];
+  vec[0].iov_base = const_cast<char*>(tag);
+  vec[0].iov_len = strlen(tag);
+  vec[1].iov_base = const_cast<char*>(": ");
+  vec[1].iov_len = 2;
+  vec[2].iov_base = const_cast<char*>(msg);
+  vec[2].iov_len = strlen(msg) + 1;
+  vec[3].iov_base = const_cast<char*>("\n");
+  vec[3].iov_len = 1;
+
+  int result = TEMP_FAILURE_RETRY(writev(fd, vec, 4));
+  close(fd);
+  return result;
+}
+
 static int __libc_write_log(int priority, const char* tag, const char* msg) {
   int main_log_fd = TEMP_FAILURE_RETRY(open("/dev/log/main", O_CLOEXEC | O_WRONLY));
   if (main_log_fd == -1) {
+    if (errno == ENOTDIR) {
+      // /dev/log isn't a directory? Maybe we're running on the host? Try stderr instead.
+      return __libc_write_stderr(tag, msg);
+    }
     return -1;
   }
 
diff --git a/linker/linker_debug.h b/linker/linker_debug.h
index 7d2485342..2bf6cec22 100644
--- a/linker/linker_debug.h
+++ b/linker/linker_debug.h
@@ -29,8 +29,6 @@
 #ifndef _LINKER_DEBUG_H_
 #define _LINKER_DEBUG_H_
 
-#include <stdio.h>
-
 // You can increase the verbosity of debug traces by defining the LD_DEBUG
 // environment variable to a numeric value from 0 to 2 (corresponding to
 // INFO, TRACE, and DEBUG calls in the source). This will only
@@ -55,9 +53,6 @@
  * To enable/disable specific debug options, change the defines above
  *********************************************************************/
 
-
-/*********************************************************************/
-
 #include "private/libc_logging.h"
 
 __LIBC_HIDDEN__ extern int gLdDebugVerbosity;