Fix backend logging from signal handlers (OpenPrinting #167)

5 files changed, 20 insertions, 9 deletions

diff --git a/backend/backend-private.h b/backend/backend-private.h
index 85fb8aef8..d19b06b82 100644
--- a/backend/backend-private.h
+++ b/backend/backend-private.h
@@ -1,7 +1,8 @@
 /*
  * Backend support definitions for CUPS.
  *
- * Copyright © 2007-2014 by Apple Inc.
+ * Copyright © 2021 by OpenPrinting
+ * Copyright © 2007-2021 by Apple Inc.
  * Copyright © 1997-2007 by Easy Software Products, all rights reserved.
  *
  * Licensed under Apache License v2.0.  See the file "LICENSE" for more
@@ -53,6 +54,14 @@ extern "C" {
 
 
 /*
+ * Log messages in backend signal handlers or other places where stdio cannot
+ * be used...
+ */
+
+#  define backendMessage(msg) {const char *s = msg; write(2, s, strlen(s));}
+
+
+/*
  * OID constants...
  */
 
@@ -320,7 +329,6 @@ extern int		backendSNMPSupplies(int snmp_fd, http_addr_t *addr,
 extern int		backendWaitLoop(int snmp_fd, http_addr_t *addr,
 			                int use_bc, _cups_sccb_t side_cb);
 
-
 #  ifdef __cplusplus
 }
 #  endif /* __cplusplus */
diff --git a/backend/ipp.c b/backend/ipp.c
index 8b1976990..63353a66d 100644
--- a/backend/ipp.c
+++ b/backend/ipp.c
@@ -3418,7 +3418,7 @@ sigterm_handler(int sig)		/* I - Signal */
 {
   (void)sig;	/* remove compiler warnings... */
 
-  write(2, "DEBUG: Got SIGTERM.\n", 20);
+  backendMessage("DEBUG: Got SIGTERM.\n");
 
 #if defined(HAVE_GSSAPI) && defined(HAVE_XPC)
   if (child_pid)
@@ -3434,7 +3434,7 @@ sigterm_handler(int sig)		/* I - Signal */
     * Flag that the job should be canceled...
     */
 
-    write(2, "DEBUG: sigterm_handler: job_canceled = 1.\n", 25);
+    backendMessage("DEBUG: sigterm_handler: job_canceled = 1.\n");
 
     job_canceled = 1;
     return;
diff --git a/backend/snmp.c b/backend/snmp.c
index 9572822a8..084c6f511 100644
--- a/backend/snmp.c
+++ b/backend/snmp.c
@@ -424,7 +424,7 @@ alarm_handler(int sig)			/* I - Signal number */
 #endif /* !HAVE_SIGSET && !HAVE_SIGACTION */
 
   if (DebugLevel)
-    write(2, "DEBUG: ALARM!\n", 14);
+    backendMessage("DEBUG: ALARM!\n");
 }
 
 
diff --git a/backend/testbackend.c b/backend/testbackend.c
index 6dbd0abee..6412a022b 100644
--- a/backend/testbackend.c
+++ b/backend/testbackend.c
@@ -19,6 +19,7 @@
 #include <fcntl.h>
 #include <sys/wait.h>
 #include <signal.h>
+#include "backend-private.h"
 
 
 /*
@@ -395,7 +396,7 @@ main(int  argc,				/* I - Number of command-line args */
 	  data = ps_data;
 
         write(1, data, strlen(data));
-	write(2, "DEBUG: START\n", 13);
+	backendMessage("DEBUG: START\n");
 	timeout = 60.0;
         while ((bytes = cupsBackChannelRead(buffer, sizeof(buffer),
 	                                    timeout)) > 0)
@@ -403,7 +404,7 @@ main(int  argc,				/* I - Number of command-line args */
 	  write(2, buffer, (size_t)bytes);
 	  timeout = 5.0;
 	}
-	write(2, "\nDEBUG: END\n", 12);
+	backendMessage("\nDEBUG: END\n");
       }
 
       exit(0);
diff --git a/backend/usb-darwin.c b/backend/usb-darwin.c
index 3f03630f0..3a8feffb6 100644
--- a/backend/usb-darwin.c
+++ b/backend/usb-darwin.c
@@ -1,5 +1,7 @@
 /*
- * Copyright 2005-2016 Apple Inc. All rights reserved.
+ * USB backend for macOS.
+ *
+ * Copyright © 2005-2021 Apple Inc. All rights reserved.
  *
  * IMPORTANT:  This Apple software is supplied to you by Apple Computer,
  * Inc. ("Apple") in consideration of your agreement to the following
@@ -2230,7 +2232,7 @@ sigterm_handler(int sig)		/* I - Signal */
       _exit(0);
     else
     {
-      write(2, "DEBUG: Child crashed.\n", 22);
+      backendMessage("DEBUG: Child crashed.\n");
       _exit(CUPS_BACKEND_STOP);
     }
   }