Save/restore errno in the debug printf functions to prevent side-effects from erasing prior errors.

Author: michaelrsweet

cups/debug.c

@@ -1,7 +1,7 @@
 //
 // Debugging functions for CUPS.
 //
-// Copyright © 2022-2024 by OpenPrinting.
+// Copyright © 2022-2026 by OpenPrinting.
 // Copyright © 2008-2018 by Apple Inc.
 //
 // Licensed under Apache License v2.0.  See the file "LICENSE" for more
@@ -85,14 +85,15 @@ _cups_debug_printf(const char *format,	// I - Printf-style format string
   char			buffer[2048];	// Output buffer
   ssize_t		bytes;		// Number of bytes in buffer
   int			level;		// Log level in message
+  int			myerrno = errno;// Copy of errno value
 
 
   // See if we need to do any logging...
   if (!debug_init)
     _cups_debug_set(getenv("CUPS_DEBUG_LOG"), getenv("CUPS_DEBUG_LEVEL"), getenv("CUPS_DEBUG_FILTER"), 0);
 
   if (_cups_debug_fd < 0)
-    return;
+    goto done;
 
   // Filter as needed...
   if (isdigit(format[0]))
@@ -101,15 +102,15 @@ _cups_debug_printf(const char *format,	// I - Printf-style format string
     level = 0;
 
   if (level > _cups_debug_level)
-    return;
+    goto done;
 
   cupsMutexLock(&debug_init_mutex);
   if (debug_filter)
     result = regexec(debug_filter, format, 0, NULL, 0);
   cupsMutexUnlock(&debug_init_mutex);
 
   if (result)
-    return;
+    goto done;
 
   // Format the message...
   gettimeofday(&curtime, NULL);
@@ -133,6 +134,10 @@ _cups_debug_printf(const char *format,	// I - Printf-style format string
   cupsMutexLock(&debug_log_mutex);
   write(_cups_debug_fd, buffer, (size_t)bytes);
   cupsMutexUnlock(&debug_log_mutex);
+
+  done:
+
+  errno = myerrno;
 }
 
 
@@ -148,14 +153,15 @@ _cups_debug_puts(const char *s)		// I - String to output
   char			buffer[2048];	// Output buffer
   ssize_t		bytes;		// Number of bytes in buffer
   int			level;		// Log level in message
+  int			myerrno = errno;// Copy of errno value
 
 
   // See if we need to do any logging...
   if (!debug_init)
     _cups_debug_set(getenv("CUPS_DEBUG_LOG"), getenv("CUPS_DEBUG_LEVEL"), getenv("CUPS_DEBUG_FILTER"), 0);
 
   if (_cups_debug_fd < 0)
-    return;
+    goto done;
 
   // Filter as needed...
   if (isdigit(s[0]))
@@ -164,15 +170,15 @@ _cups_debug_puts(const char *s)		// I - String to output
     level = 0;
 
   if (level > _cups_debug_level)
-    return;
+    goto done;
 
   cupsMutexLock(&debug_init_mutex);
   if (debug_filter)
     result = regexec(debug_filter, s, 0, NULL, 0);
   cupsMutexUnlock(&debug_init_mutex);
 
   if (result)
-    return;
+    goto done;
 
   // Format the message...
   gettimeofday(&curtime, NULL);
@@ -192,6 +198,10 @@ _cups_debug_puts(const char *s)		// I - String to output
   cupsMutexLock(&debug_log_mutex);
   write(_cups_debug_fd, buffer, (size_t)bytes);
   cupsMutexUnlock(&debug_log_mutex);
+
+  done:
+
+  errno = myerrno;
 }