Re: [gmime-devel] GObject unref hell

[Mario Theodoridis <mario theodoridis regify com>]

On 06/11/13 13:31, Jeffrey Stedfast wrote:
> On 11/6/2013 4:21 AM, Mario Theodoridis wrote:
>> ....
> > 2. Is there a way to safely unref a GObject, i.e. unref it if it needs
> > to be? This is mainly because it is not always clear to me when and
> > when not due to issues like the current.
>
> No, but as a general set of rules:
>
> 1. if you create a new object and set it as a child on another object,
> you need to unref it
> 2. when you get an object from another object, you don't - think if it
> as returning a const pointer.
>
> example of rule #1:
>
> child = g_mime_child_new ();
> g_mime_parent_add_child (parent, child);
> g_object_unref (child);
>
> The reason you unref here is because the parent adds a ref to the child
> when you add it.
>
> Essentially you own a ref to child, and, once you've added the child to
> the parent, the parent *also* owns a ref to the child. Thus there are 2
> references to it, but if you are done with the child, you need to unref
> it (or you leak a reference to it).
>
> example of rule #2:
>
> child = g_mime_parent_get_child (parent);
> // no need to unref child because the parent does not ref the child when
> it returns it
>
> // to extend this example further...
> g_mime_parent_add_child (parent2, child);
> // still don't unref the child because you never ref'd it
>
> In this example, when you get the child from the parent, only the parent
> owns a reference to the child. When you add it to parent2, parent2 adds
> another reference, which means that now both parent objects own a ref to
> the child, but since you still don't own a reference to the child, you
> don't unref it.

Yes , this is how i understood it, too.
But i'm still getting these weired errors.
Lookin at the error log, i have a feeling it happens in
> g_mime_message_set_mime_part (message, (GMimeObject*) multipart);
when the old mime_part gets unrefed.

Here's the complete function with error checking removed for brevity.
It rewrites an existing message to reflect its new structure.

msg->message is of type GMimeMessage * and
msg->headerList of GMimeHeaderList *


int mimeFromRgsMsg(msgObj msg, rgsMsg rgMsg) {
    uint attCnt = 0;
    GMimeDataWrapper *content = NULL;
    GMimeStream *mem = NULL;
    GMimePart *part = NULL;
    GMimeMultipart *multipart = NULL;
    char *res = NULL;
    size_t resLen = 0;
    rgsAtt att = NULL;
    char *fileName = NULL;
    char *type = NULL, *subtype = NULL, *param = NULL, *value = NULL;
    GMimeHeaderList *oldHeaderList = NULL;
    GMimeHeaderIter *iter = NULL;

    do {

        /* make the main body first */

        /* get the body */
        rgsGet(rgMsg, RGS_BODY, &res);

        /* find type */
        getType(msg, res, strlen(res), &type, &subtype, &param, &value);

        mem = g_mime_stream_mem_new_with_buffer (res, strlen (res));
        content = g_mime_data_wrapper_new_with_stream ((GMimeStream *) mem,

GMIME_CONTENT_ENCODING_DEFAULT);
        rfunref (mem);

        part = g_mime_part_new_with_type (type, subtype);
        g_mime_object_set_content_type_parameter ((GMimeObject *) part,
                                                  param, value);
        if (g_ascii_strcasecmp(type, "text") == 0) {
            g_mime_part_set_content_encoding(
                    part, GMIME_CONTENT_ENCODING_QUOTEDPRINTABLE);
        } else {
            g_mime_part_set_content_encoding (
                    part, GMIME_CONTENT_ENCODING_BASE64);
        }
        g_mime_part_set_content_object (part, content);
        rfunref (content);

        /* get a list of the old headers so we can delete what's no longer
         * needed */
        oldHeaderList = 
g_mime_object_get_header_list(msg->message->mime_part);
        iter = g_mime_header_iter_new();
        if(g_mime_header_list_get_iter(oldHeaderList, iter)) {
            msg->oldHeaders = g_array_new(FALSE, FALSE, sizeof (char*));
            do {
                char* name = 
g_strdup((char*)g_mime_header_iter_get_name(iter));
                g_array_append_val(msg->oldHeaders, name);
            } while(g_mime_header_iter_next (iter));
        }
        if (iter) g_mime_header_iter_free(iter);
        iter = NULL;

        /* yank the body and rgf attachment */
        if (GMIME_IS_MULTIPART (msg->message->mime_part)) {
            g_mime_multipart_clear((GMimeMultipart 
*)msg->message->mime_part);
        }

        rgsGetAttachmentCount(rgMsg, &attCnt);

        if (attCnt == 0) {
            /* remove unneeded multi part */
            g_mime_message_set_mime_part (msg->message, (GMimeObject*) 
part);
            msg->headerList = 
g_mime_object_get_header_list((GMimeObject*)part);
            rfunref (part);
            break;
        }

        /* there are many parts */
        multipart = g_mime_multipart_new_with_subtype ("mixed");
        g_mime_multipart_add (multipart, (GMimeObject *) part);
        rfunref (part);
        part = NULL;

        do {
            rgsGetAttachment(rgMsg, &att);
            if (!att) break; /* we're done */

            rgsAttGetName(att, &fileName);

            /* get attachment data */
            rgsAttGetData(att, (void**) &res, &resLen);

            mem = g_mime_stream_mem_new_with_buffer (res, resLen);
            content = g_mime_data_wrapper_new_with_stream (
                        (GMimeStream*)mem, GMIME_CONTENT_ENCODING_DEFAULT);
            rfunref (mem);

            /* find type */
            getType(msg, res, resLen, &type, &subtype, &param, &value);

            part = g_mime_part_new_with_type(type, subtype);
            g_mime_part_set_filename(part, fileName);
            g_mime_object_set_content_type_parameter((GMimeObject*)part,
                                                     param, value);
            if (g_ascii_strcasecmp(type, "text") == 0) {
                g_mime_part_set_content_encoding(
                        part, GMIME_CONTENT_ENCODING_QUOTEDPRINTABLE);
            } else {
                g_mime_part_set_content_encoding (
                        part, GMIME_CONTENT_ENCODING_BASE64);
            }
            g_mime_part_set_content_object (part, content);
            rfunref (content);

            g_mime_multipart_add (multipart, (GMimeObject *) part);
            rfunref (part);

        } while(TRUE);

        g_mime_message_set_mime_part (msg->message, (GMimeObject*) 
multipart);
        msg->headerList = 
g_mime_object_get_header_list((GMimeObject*)multipart);
        rfunref (multipart);

    } while(FALSE);

    rfunref (mem);
    rfunref (content);
    rfunref (part);
    rfunref (multipart);

    return 0;
}



--
Mit Freundlichen Grüßen / Regards

Mario Theodoridis

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