Make libppd safe to use from several threads

Makefile.am

@@ -67,7 +67,8 @@ check_PROGRAMS = \
 	test_ppd_emit \
 	test_ppd_filter \
 	test_ppd_generator \
-	test_ppd_load_profile
+	test_ppd_load_profile \
+	test_ppd_thread
 TESTS = \
 	testppd \
 	test_ppd_localize \
@@ -81,7 +82,8 @@ TESTS = \
 	test_ppd_emit \
 	test_ppd_filter \
 	test_ppd_generator \
-	test_ppd_load_profile
+	test_ppd_load_profile \
+	test_ppd_thread
 
 libppd_la_SOURCES = \
 	ppd/ppd-attr.c \
@@ -267,6 +269,15 @@ test_ppd_load_profile_CFLAGS = \
 	$(CUPS_CFLAGS) \
 	$(LIBCUPSFILTERS_CFLAGS)
 
+test_ppd_thread_SOURCES = ppd/test_ppd_thread.c
+test_ppd_thread_LDADD = \
+	libppd.la \
+	$(CUPS_LIBS)
+test_ppd_thread_CFLAGS = \
+	-I$(srcdir)/ppd/ \
+	-pthread \
+	$(CUPS_CFLAGS)
+
 EXTRA_DIST += \
 	$(pkgppdinclude_DATA) \
 	$(pkgppddefs_DATA) \

configure.ac

@@ -257,6 +257,11 @@ AC_CHECK_HEADERS([dirent.h])
 AC_CHECK_HEADER(string.h,AC_DEFINE(HAVE_STRING_H))
 AC_CHECK_HEADER(strings.h,AC_DEFINE(HAVE_STRINGS_H))
 
+# ===================================================================
+# Check for POSIX threads (mutexes and per-thread data of the library)
+# ===================================================================
+AC_CHECK_HEADERS([pthread.h], [AC_SEARCH_LIBS([pthread_key_create], [pthread])])
+
 # ===================================
 # Check for large files and long long
 # ===================================

ppd/ppd-cache.c

@@ -13,6 +13,7 @@
 //
 
 #include <ppd/string-private.h>
+#include <ppd/thread-private.h>
 #include <ppd/array-private.h>
 #include <ppd/ipp-private.h>
 #include <ppd/ppd.h>
@@ -76,6 +77,8 @@ static int	ppd_pwg_compare_finishings(ppd_pwg_finishings_t *a,
 static void	ppd_pwg_free_finishings(ppd_pwg_finishings_t *f);
 
 char            *ppd_cache_status_message = NULL; // Last PPD cache error
+static _ppd_mutex_t	ppd_cache_status_mutex = _PPD_MUTEX_INITIALIZER;
+					// Mutex to control access to it
 
 
 //
@@ -86,19 +89,16 @@ static void
 set_error(const char   *message,	// I - status-message value
 	  int          localize)	// I - Localize the message?
 {
+  char	*new_message = NULL,		// New status-message
+	*old_message;			// Previous status-message
+
+
   if (!message && errno)
   {
     message  = strerror(errno);
     localize = 0;
   }
 
-  if (ppd_cache_status_message)
-  {
-    _ppdStrFree(ppd_cache_status_message);
-
-    ppd_cache_status_message = NULL;
-  }
-
   if (message)
   {
     if (localize)
@@ -107,16 +107,26 @@ set_error(const char   *message,	// I - status-message value
      // Get the message catalog...
      //
 
-      ppd_cache_status_message =
-	_ppdStrAlloc(cupsLangGetString(cupsLangDefault(),
-				      message));
+      new_message = _ppdStrAlloc(cupsLangGetString(cupsLangDefault(),
+						   message));
     }
     else
-      ppd_cache_status_message = _ppdStrAlloc(message);
+      new_message = _ppdStrAlloc(message);
   }
 
-  DEBUG_printf(("4set_error: last_status_message=\"%s\"",
-                ppd_cache_status_message));
+  DEBUG_printf(("4set_error: last_status_message=\"%s\"", new_message));
+
+  //
+  // Swap in the new message and free the previous one, so that threads
+  // setting errors at the same time never free the same string twice...
+  //
+
+  _ppdMutexLock(&ppd_cache_status_mutex);
+  old_message              = ppd_cache_status_message;
+  ppd_cache_status_message = new_message;
+  _ppdMutexUnlock(&ppd_cache_status_mutex);
+
+  _ppdStrFree(old_message);
 }
 
 //

ppd/raster-error.c

@@ -13,6 +13,7 @@
 //
 
 #include "raster-private.h"
+#include "thread-private.h"
 #include "debug-internal.h"
 
 typedef struct _ppd_raster_error_s	// **** Error buffer structure ****
@@ -22,7 +23,32 @@ typedef struct _ppd_raster_error_s	// **** Error buffer structure ****
 	*end;				// End of buffer
 } _ppd_raster_error_t;
 
-static _ppd_raster_error_t	*buf = NULL;
+
+//
+// Local globals...
+//
+
+#ifdef HAVE_PTHREAD_H
+static _ppd_threadkey_t	ppd_raster_error_key = _PPD_THREADKEY_INITIALIZER;
+					// Thread local storage key
+static pthread_once_t	ppd_raster_error_key_once = PTHREAD_ONCE_INIT;
+					// One-time initialization object
+#else
+static _ppd_raster_error_t ppd_raster_error_buf = { NULL, NULL, NULL };
+					// Error buffer
+#endif // HAVE_PTHREAD_H
+
+
+//
+// Local functions...
+//
+
+static _ppd_raster_error_t	*ppd_raster_error_buffer(void);
+#ifdef HAVE_PTHREAD_H
+static void			ppd_raster_error_free(void *data);
+static void			ppd_raster_error_init(void);
+#endif // HAVE_PTHREAD_H
+
 
 //
 // '_ppdRasterAddError()' - Add an error message to the error buffer.
@@ -32,13 +58,18 @@ void
 _ppdRasterAddError(const char *f,	// I - Printf-style error message
                     ...)		// I - Additional arguments as needed
 {
+  _ppd_raster_error_t	*buf = ppd_raster_error_buffer();
+					// Error buffer for this thread
   va_list	ap;			// Pointer to additional arguments
   char		s[2048];		// Message string
   ssize_t	bytes;			// Bytes in message string
 
 
   DEBUG_printf(("_ppdRasterAddError(f=\"%s\", ...)", f));
 
+  if (!buf)
+    return;
+
   va_start(ap, f);
   bytes = vsnprintf(s, sizeof(s), f, ap);
   va_end(ap);
@@ -98,13 +129,12 @@ _ppdRasterAddError(const char *f,	// I - Printf-style error message
 void
 _ppdRasterClearError(void)
 {
-  if (buf == NULL)
-  {
-    buf = malloc(sizeof(_ppd_raster_error_t));
-    buf->start = NULL;
-    buf->end = NULL;
-    buf->current = NULL;
-  }
+  _ppd_raster_error_t	*buf = ppd_raster_error_buffer();
+					// Error buffer for this thread
+
+
+  if (!buf)
+    return;
 
   buf->current = buf->start;
 
@@ -124,8 +154,77 @@ _ppdRasterClearError(void)
 const char *				// O - Last error
 _ppdRasterErrorString(void)
 {
-  if (buf->current == buf->start)
+  _ppd_raster_error_t	*buf = ppd_raster_error_buffer();
+					// Error buffer for this thread
+
+
+  if (!buf || buf->current == buf->start)
     return (NULL);
   else
     return (buf->start);
 }
+
+
+//
+// 'ppd_raster_error_buffer()' - Return the error buffer of the current thread.
+//
+
+static _ppd_raster_error_t *		// O - Error buffer or NULL
+ppd_raster_error_buffer(void)
+{
+#ifdef HAVE_PTHREAD_H
+  _ppd_raster_error_t	*buf;		// Error buffer
+
+
+  //
+  // Initialize the thread key exactly once...
+  //
+
+  pthread_once(&ppd_raster_error_key_once, ppd_raster_error_init);
+
+  //
+  // Allocate the buffer of this thread on first use...
+  //
+
+  if ((buf = (_ppd_raster_error_t *)
+	     _ppdThreadGetData(ppd_raster_error_key)) == NULL)
+  {
+    if ((buf = calloc(1, sizeof(_ppd_raster_error_t))) != NULL)
+      _ppdThreadSetData(ppd_raster_error_key, buf);
+  }
+
+  return (buf);
+
+#else
+  return (&ppd_raster_error_buf);
+#endif // HAVE_PTHREAD_H
+}
+
+
+#ifdef HAVE_PTHREAD_H
+//
+// 'ppd_raster_error_free()' - Free the error buffer of a thread that exits.
+//
+
+static void
+ppd_raster_error_free(void *data)	// I - Error buffer
+{
+  _ppd_raster_error_t	*buf = (_ppd_raster_error_t *)data;
+					// Error buffer
+
+
+  free(buf->start);
+  free(buf);
+}
+
+
+//
+// 'ppd_raster_error_init()' - Create the thread key for the error buffers.
+//
+
+static void
+ppd_raster_error_init(void)
+{
+  pthread_key_create(&ppd_raster_error_key, ppd_raster_error_free);
+}
+#endif // HAVE_PTHREAD_H