gdbus: is it safe to free signal argument right after signal emission

Question

I created simple dbus service that emits signal with dynamically allocated data argument:

file_name = g_strdup("myfile");
...
...
g_signal_emit_by_name (object, "mysignal", file_name);
g_free(file_name);

In this case signal listeners may receive file_name string that was already destroyed.

So is it safe to free file_name right after g_signal_emit_by_name call or I should wait for a few seconds? Or is there any other mechanism to free memory in such cases?

score 3 · Accepted Answer · answered Feb 03 '14 at 11:44

3

GSignal emission is synchronous, i.e. all the connected callbacks to a signal are run sequentially by g_signal_emit(), which will return control to you once all callbacks return. thus, it is safe to emit a signal and free the arguments of the signal after g_signal_emit() returns.

if you're using DBus then it's still safe: the data will be copied over to the receiving process(es), as it would be impossible to share it across process boundaries.

answered Feb 03 '14 at 11:44

ebassi

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Do I need to free this data in the receiver? – user1780084 Feb 06 '14 at 01:46
it entirely depends on the API you use in the receiver. – ebassi Feb 06 '14 at 11:17
typically it would be a bad idea to have data sent with g_signal_emit freed by receivers, since there could be multiple ones; better to handle it on the sender side. – djcb Feb 20 '14 at 20:23

score 0 · Answer 2 · answered Feb 03 '14 at 04:25

0

I'm not familiar with the gdbus API in particular, but in general for this kind of usage, you want to make it the recipient's responsibility to free the storage. The only exceptions would be when the object is known to have a lifetime that will persist beyond the needs of the recipient (e.g. static storage) or the API handles copying data for you.

answered Feb 03 '14 at 04:25

R.. GitHub STOP HELPING ICE

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well, (as i said above) you can connect any number of receivers to the signal and you need to free the storage only once... so better to do it after g_signal_emit returns. – djcb Feb 20 '14 at 20:26

gdbus: is it safe to free signal argument right after signal emission

2 Answers2