[PATCH] notmuch_message_file_get_header: use talloc for hash table entries

[david at tethera.net]

From: David Bremner <bremner at debian.org>

Before this patch there is some strange mix of malloc/free and
g_malloc/g_free.  In particular, the pointer returned by
g_mime_utils_header_decode_text is from the following line in
rfc2047_decode_tokens

	return g_string_free (decoded, FALSE);

The docs for g_string_free say

 Frees the memory allocated for the GString. If free_segment is TRUE
 it also frees the character data. If it's FALSE, the caller gains
 ownership of the buffer and must free it after use with g_free().

On the other hand, as Tomi points out in id:m2a9tlfaza.fsf at guru.guru-group.fi,
Sometimes the string is allocated with with xmalloc.

This patch tries to unify everything to use talloc.

Because of difficulties in error handling in a callback, we defer
deallocation of hash entries to when the parent context (the message)
is destroyed.

The function talloc_str_from_g might be overkill; it is currently only
used once.
---
 lib/message-file.c |   35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/lib/message-file.c b/lib/message-file.c
index 915aba8..f84e929 100644
--- a/lib/message-file.c
+++ b/lib/message-file.c
@@ -73,6 +73,15 @@ strcase_hash (const void *ptr)
     return hash;
 }
 
+static inline
+char *talloc_str_from_g (void *ctx, char *str)
+{
+    char *dup = talloc_strdup (ctx, str);
+    g_free(str);
+
+    return dup;
+}
+
 static int
 _notmuch_message_file_destructor (notmuch_message_file_t *message)
 {
@@ -108,10 +117,13 @@ _notmuch_message_file_open_ctx (void *ctx, const char *filename)
     if (message->file == NULL)
 	goto FAIL;
 
+    /* We choose not to pass talloc_free (or some wrapper), because we have no
+     * good way of dealing with its failure condition.
+     */
     message->headers = g_hash_table_new_full (strcase_hash,
 					      strcase_equal,
-					      free,
-					      free);
+					      NULL,
+					      NULL);
 
     message->parsing_started = 0;
     message->parsing_finished = 0;
@@ -151,7 +163,7 @@ notmuch_message_file_restrict_headersv (notmuch_message_file_t *message,
 	if (header == NULL)
 	    break;
 	g_hash_table_insert (message->headers,
-			     xstrdup (header), NULL);
+			     talloc_strdup (message, header), NULL);
     }
 
     message->restrict_headers = 1;
@@ -299,13 +311,13 @@ notmuch_message_file_get_header (notmuch_message_file_t *message,
 
 	message->good_headers++;
 
-	header = xstrndup (message->line, colon - message->line);
+	header = talloc_strndup (message, message->line, colon - message->line);
 
 	if (message->restrict_headers &&
 	    ! g_hash_table_lookup_extended (message->headers,
 					    header, NULL, NULL))
 	{
-	    free (header);
+	    talloc_free (header);
 	    NEXT_HEADER_LINE (NULL);
 	    continue;
 	}
@@ -324,7 +336,10 @@ notmuch_message_file_get_header (notmuch_message_file_t *message,
 	else
 	    match = (strcasecmp (header, header_desired) == 0);
 
-	decoded_value = g_mime_utils_header_decode_text (message->value.str);
+	decoded_value =
+	    talloc_str_from_g (message,
+			   g_mime_utils_header_decode_text (message->value.str));
+
 	header_sofar = (char *)g_hash_table_lookup (message->headers, header);
 	/* we treat the Received: header special - we want to concat ALL of 
 	 * the Received: headers we encounter.
@@ -337,11 +352,11 @@ notmuch_message_file_get_header (notmuch_message_file_t *message,
 		/* we need to add the header to those we already collected */
 		newhdr = strlen(decoded_value);
 		hdrsofar = strlen(header_sofar);
-		combined_header = xmalloc(hdrsofar + newhdr + 2);
+		combined_header = talloc_size (message, hdrsofar + newhdr + 2);
 		strncpy(combined_header,header_sofar,hdrsofar);
 		*(combined_header+hdrsofar) = ' ';
 		strncpy(combined_header+hdrsofar+1,decoded_value,newhdr+1);
-		free (decoded_value);
+		talloc_free (decoded_value);
 		g_hash_table_insert (message->headers, header, combined_header);
 	    }
 	} else {
@@ -349,8 +364,8 @@ notmuch_message_file_get_header (notmuch_message_file_t *message,
 		/* Only insert if we don't have a value for this header, yet. */
 		g_hash_table_insert (message->headers, header, decoded_value);
 	    } else {
-		free (header);
-		free (decoded_value);
+		talloc_free (header);
+		talloc_free (decoded_value);
 		decoded_value = header_sofar;
 	    }
 	}
-- 
1.7.10.4