GNOME Bugzilla – Bug 479787
Calling "g_main_context_pending" increases reference count for the ready sources
Last modified: 2018-05-24 11:06:49 UTC
Please describe the problem: Calling "g_main_context_pending" increases reference count for the ready sources, in the internal call to g_main_context_check. This function calls internal "g_main_context_iterate", with "dispatch" parameter set to "FALSE". Normally, whenever g_main_context_iterate is called with "dispatch" parameter set to "TRUE", internal call of "g_main_context_dispatch" decreases the reference count of the dispatched sources. Steps to reproduce: 1. 4 sources are attached to the newly created context, two of which with priority "-1" and two others with "1" and "2". 2. First two sources will be marked as "READY" after internal call of "g_main_context_check" and reference count for them will be increased. If "g_main_context_pending" would not have been called here, the following warnings would appear after the invocation of "g_main_context_unref" in the "for": //********************************************************************* (process:7320): GLib-WARNING **: gmain.c:1417: ref_count == 0, but source is still attached to a context! (process:7320): GLib-WARNING **: gmain.c:1417: ref_count == 0, but source is still attached to a context! //********************************************************************* The absence of these warnings upon invocation of the sample shows that reference count for ready sources was increased during the call to "g_main_context_pending". The detailed bug description can be found at: http://linuxtesting.org/results/report?num=D0006
Created attachment 96112 [details] The test case reproducing the bug
Created attachment 333422 [details] [review] proposed fix I've also identified this bug during code reading. What about adding g_main_context_check_ref() to control refcounting and making g_main_context_check() calls it (with TRUE)?
Hi, Areg & Namhyung. @ Areg As I read the API, Areg need to use g_source_destroy() instead of calling g_source_unref() directly. @ Namhyung It seems sane to increase the ref count of the ready sources which are inserted to context->pending_dispatches, by calling g_main_context_pending(). The ref count of that sources will be un-ref when the sources are dispatched or the context is freed.
Hello Hyungwon, Thanks for the review. I was not sure how this API is used. It seems g_main_context_pending() followed by g_main_context_dispatch() would be fine, but if not, there will be a leak. I think it's better protecting the resource from the API misuse or adding some comment about this at least.
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