Save and restore the value of GetLastError() when [D]LOG/[D]CHECK etc on Windows.

Also for log levels higher than INFO, the value of GLE is tagged onto the log message.

Review URL: http://codereview.chromium.org/73010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@13667 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 28 insertions, 0 deletions

diff --git a/base/logging.cc b/base/logging.cc
index 41a0933..961ea6c 100644
--- a/base/logging.cc
+++ b/base/logging.cc
@@ -342,6 +342,15 @@ void DisplayDebugMessage(const std::string& str) {
 #endif
 }
 
+#if defined(OS_WIN)
+LogMessage::SaveLastError::SaveLastError() : last_error_(::GetLastError()) {
+}
+
+LogMessage::SaveLastError::~SaveLastError() {
+  ::SetLastError(last_error_);
+}
+#endif  // defined(OS_WIN)
+
 LogMessage::LogMessage(const char* file, int line, LogSeverity severity,
                        int ctr)
     : severity_(severity) {
diff --git a/base/logging.h b/base/logging.h
index b3bba0b..6a58cf3 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -540,6 +540,25 @@ class LogMessage {
   std::ostringstream stream_;
   size_t message_start_;  // Offset of the start of the message (past prefix
                           // info).
+#if defined(OS_WIN)
+  // Stores the current value of GetLastError in the constructor and restores
+  // it in the destructor by calling SetLastError.
+  // This is useful since the LogMessage class uses a lot of Win32 calls
+  // that will lose the value of GLE and the code that called the log function
+  // will have lost the thread error value when the log call returns.
+  class SaveLastError {
+   public:
+    SaveLastError();
+    ~SaveLastError();
+
+    unsigned long get_error() const { return last_error_; }
+
+   protected:
+    unsigned long last_error_;
+  };
+
+  SaveLastError last_error_;
+#endif
 
   DISALLOW_COPY_AND_ASSIGN(LogMessage);
 };