Use native os_log APIs on OSX for PowerShell logging (PowerShell#5310)

src/libpsl-native/src/nativesyslog.cpp

@@ -2,18 +2,65 @@
 //! @brief Provides wrappers around the syslog apis to support exporting
 //! for PInvoke calls by powershell.
 //! These functions are intended only for PowerShell internal use.
+//! To view log output in real time
+//! On Linux
+//!    tail -f /var/log/syslog | grep powershell 
+//!  On OSX
+//!    sudo log stream
+//!  NOTE: replace powershell with the LogIdentity value when overriding in configuration
 #include <syslog.h>
 #include <nativesyslog.h>
 
+#if defined(__APPLE__) && defined(__MACH__)
+
+#include <os/log.h>
+#include <stdio.h>
+static os_log_t _log = NULL;
+
+// This format string ensures the message string for the log statements
+// are visible. Using just %s marks them as private and the do not show
+// up with log stream.
+#define MESSAGE_FORMAT "%{public}s"
+
+// The submodule name to pass to os_log_create.
+// The passed in ident value will be used for the category.
+// see man os_log_create
+#define SUBMODULE_NAME "com.microsoft.powershell"
+
+#endif
+
 //! @brief Native_SysLog is a wrapper around the syslog api.
 //! It explicitly passes the message as a parameter to a %s format
-//! string since the message may have arbitray characters that can
+//! string since the message may have arbitrary characters that can
 //! be misinterpreted as format specifiers.
 //!
 //! @retval none.
 extern "C" void Native_SysLog(int32_t priority, const char* message)
 {
+#if defined(__APPLE__) && defined(__MACH__)
+    switch (priority)
+    {
+        case LOG_EMERG:
+        case LOG_ALERT:
+        case LOG_CRIT:
+            os_log_fault(_log, MESSAGE_FORMAT, message);
+            break;
+
+        case LOG_ERR:
+            os_log_error(_log, MESSAGE_FORMAT, message);
+            break;
+
+        case LOG_DEBUG:
+            os_log_debug(_log, MESSAGE_FORMAT, message);
+            break;
+
+        default:
+            os_log(_log, MESSAGE_FORMAT, message);
+            break;        
+    }
+#else
     syslog(priority, "%s", message);
+#endif
 }
 
 //! @brief Native_OpenLog is a wrapper around the openlog, syslog api.
@@ -23,13 +70,21 @@ extern "C" void Native_SysLog(int32_t priority, const char* message)
 //! @retval none.
 extern "C" void Native_OpenLog(const char* ident, int facility)
 {
+#if defined(__APPLE__) && defined(__MACH__)
+    _log = os_log_create(SUBMODULE_NAME, ident);
+#else
     openlog(ident, LOG_NDELAY | LOG_PID, facility);
+#endif
 }
 
 //! @brief Native_OpenLog is a wrapper around the closelog, syslog api.
 //!
 //! @retval none.
 extern "C" void Native_CloseLog()
 {
+#if defined(__APPLE__) && defined(__MACH__)
+    // Nothing to do here now, for now.
+#else 
     closelog();
+#endif
 }