Support throwing an exception with a null message pointer, and have the

message not be const (as we generate messages with "g_strdup_sprintf()",
which means they need to be freed; using a null message means that we
don't have to use a special string for exceptions with no message, and
don't have to worry about not freeing that).

Have THROW() throw an exception with a null message pointer.  (This
means that you crash if you throw DissectorError with THROW().  Don't do
that - it means you don't get a more detailed explanation of the
dissector problem.  Use the DISSECTOR_ASSERT, etc. macros in
epan/proto.h instead.)

Free the exception message for DissectorError, as it's mallocated.

svn path=/trunk/; revision=15250

epan/dissectors/packet-frame.c

@@ -288,6 +288,7 @@ show_exception(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 		    pinfo->current_proto, exception_message);
 		g_warning("Dissector bug, protocol %s, in packet %u: %s",
 		    pinfo->current_proto, pinfo->fd->num, exception_message);
+		g_free(exception_message);
 		break;
 
 	default:

epan/except.c

@@ -17,6 +17,15 @@
  * $Name:  $
  */
 
+/*
+ * Modified to support throwing an exception with a null message pointer,
+ * and to have the message not be const (as we generate messages with
+ * "g_strdup_sprintf()", which means they need to be freed; using
+ * a null message means that we don't have to use a special string
+ * for exceptions with no message, and don't have to worry about
+ * not freeing that).
+ */
+
 #include <assert.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -194,9 +203,15 @@ static void do_throw(except_t *except)
 
 static void unhandled_catcher(except_t *except)
 {
-    fprintf(stderr, "Unhandled exception (\"%s\", group=%ld, code=%ld)\n",
-	    except->except_message, except->except_id.except_group,
-	    except->except_id.except_code);
+    if (except->except_message == NULL) {
+        fprintf(stderr, "Unhandled exception (group=%ld, code=%ld)\n",
+		except->except_id.except_group,
+		except->except_id.except_code);
+    } else {
+        fprintf(stderr, "Unhandled exception (\"%s\", group=%ld, code=%ld)\n",
+		except->except_message, except->except_id.except_group,
+		except->except_id.except_code);
+    }
     abort();
 }
 
@@ -244,7 +259,7 @@ void except_rethrow(except_t *except)
     do_throw(except);
 }
 
-void except_throw(long group, long code, const char *msg)
+void except_throw(long group, long code, char *msg)
 {
     except_t except;
 
@@ -256,7 +271,7 @@ void except_throw(long group, long code, const char *msg)
     do_throw(&except);
 }
 
-void except_throwd(long group, long code, const char *msg, void *data)
+void except_throwd(long group, long code, char *msg, void *data)
 {
     except_t except;
 
@@ -268,6 +283,11 @@ void except_throwd(long group, long code, const char *msg, void *data)
     do_throw(&except);
 }
 
+/*
+ * XXX - should we use g_strdup_sprintf() here, so we're not limited by
+ * XCEPT_BUFFER_SIZE?  We could then just use this to generate formatted
+ * messages.
+ */
 void except_throwf(long group, long code, const char *fmt, ...)
 {
     char *buf = except_alloc(XCEPT_BUFFER_SIZE);
@@ -301,7 +321,7 @@ unsigned long except_group(except_t *ex)
     return ex->except_id.except_group;
 }
 
-const char *except_message(except_t *ex)
+char *except_message(except_t *ex)
 {
     return ex->except_message;
 }
@@ -369,6 +389,7 @@ int main(int argc, char **argv)
 {
     static const except_id_t catch[] = { { 1, 1 }, { 1, 2 } };
     except_t *ex;
+    char *msg;
 
     /*
      * Nested exception ``try blocks''
@@ -383,15 +404,27 @@ int main(int argc, char **argv)
 	    top_level();
 	} else {
 	    /* inner catch */
-	    printf("caught exception (inner): \"%s\", s=%ld, c=%ld\n",
-		    except_message(ex), except_group(ex), except_code(ex));
+	    msg = except_message(ex);
+	    if (msg == NULL) {
+		printf("caught exception (inner): s=%ld, c=%ld\n",
+		       except_group(ex), except_code(ex));
+	    } else {
+		printf("caught exception (inner): \"%s\", s=%ld, c=%ld\n",
+		       msg, except_group(ex), except_code(ex));
+	    }
 	    except_rethrow(ex);
 	}
 	except_try_pop();
     } else {
 	/* outer catch */
-	printf("caught exception (outer): \"%s\", s=%ld, c=%ld\n",
-		except_message(ex), except_group(ex), except_code(ex));
+	msg = except_message(ex);
+	if (msg == NULL) {
+	    printf("caught exception (outer): s=%ld, c=%ld\n",
+		   except_group(ex), except_code(ex));
+	} else {
+	    printf("caught exception (outer): \"%s\", s=%ld, c=%ld\n",
+		   except_message(ex), except_group(ex), except_code(ex));
+	}
     }
     except_try_pop();
     except_throw(99, 99, "exception in main");

epan/except.h

@@ -18,6 +18,15 @@
  * $Name:  $
  */
 
+/*
+ * Modified to support throwing an exception with a null message pointer,
+ * and to have the message not be const (as we generate messages with
+ * "g_strdup_sprintf()", which means they need to be freed; using
+ * a null message means that we don't have to use a special string
+ * for exceptions with no message, and don't have to worry about
+ * not freeing that).
+ */
+
 #ifndef XCEPT_H
 #define XCEPT_H
 
@@ -42,7 +51,7 @@ typedef struct {
 
 typedef struct {
     except_id_t volatile except_id;
-    const char *volatile except_message;
+    char *volatile except_message;
     void *volatile except_dyndata;
 } except_t;
 
@@ -82,13 +91,13 @@ extern struct except_stacknode *except_pop(void);
 extern int except_init(void);
 extern void except_deinit(void);
 extern void except_rethrow(except_t *);
-extern void except_throw(long, long, const char *);
-extern void except_throwd(long, long, const char *, void *);
+extern void except_throw(long, long, char *);
+extern void except_throwd(long, long, char *, void *);
 extern void except_throwf(long, long, const char *, ...);
 extern void (*except_unhandled_catcher(void (*)(except_t *)))(except_t *);
 extern unsigned long except_code(except_t *);
 extern unsigned long except_group(except_t *);
-extern const char *except_message(except_t *);
+extern char *except_message(except_t *);
 extern void *except_data(except_t *);
 extern void *except_take_data(except_t *);
 extern void except_set_allocator(void *(*)(size_t), void (*)(void *));

epan/exceptions.h

@@ -46,7 +46,13 @@
 #define TypeError		3
 
 /**
-    A bug was detected in a dissector 
+    A bug was detected in a dissector.
+
+    DO NOT throw this with THROW(); the handler expects there to be a
+    message, and even if it didn't, the developers expect there to be
+    a message to make it easier to figure out what the problem is.
+
+    Instead, use the DISSECTOR_ASSERT(), etc. macros in epan/proto.h.
 **/
 #define DissectorError		4	
 
@@ -195,7 +201,7 @@
 		/* user's code goes here */
 
 #define THROW(x) \
-	except_throw(XCEPT_GROUP_ETHEREAL, (x), "XCEPT_GROUP_ETHEREAL")
+	except_throw(XCEPT_GROUP_ETHEREAL, (x), NULL)
 
 #define THROW_MESSAGE(x, y) \
 	except_throw(XCEPT_GROUP_ETHEREAL, (x), (y))