GC-proof resource classes
ponce via Digitalmars-d
digitalmars-d at puremagic.com
Sun Aug 30 13:44:15 PDT 2015
On Sunday, 30 August 2015 at 17:00:23 UTC, ZombineDev wrote:
> On Saturday, 29 August 2015 at 13:14:26 UTC, ponce wrote:
>>
>> ----------------
>>
>> ensureNotInGC() is implemented like this:
>>
>> ----------------
>>
>> void ensureNotInGC(string resourceName) nothrow
>> {
>> debug
>> {
>> import core.exception;
>> try
>> {
>> import core.memory;
>> void* p = GC.malloc(1); // not ideal since it
>> allocates
>> return;
>> }
>> catch(InvalidMemoryOperationError e)
>> {
>> import core.stdc.stdio;
>> fprintf(stderr, "Error: clean-up of %s incorrectly
>> depends on destructors called by the GC.\n", resourceName.ptr);
>> assert(false); // crash
>> }
>> }
>> }
>>
>> --------------
>>
>>...
>
> BTW, you can use GC.free, instead of GC.malloc, with any
> non-zero invalid memory address, for example:
> http://dpaste.dzfl.pl/af0dc9aaa29d
>
In the case the destructor isn't called by the GC, the call must
succeed.
GC.malloc(1) fits the bill but it's a waste of time and memory
indeed. GC.free(<invalid-adress>) would fail in both cases if I
understand correctly.
> A more robust solution would be to check if the gcx.running
> flag is raised, or if the GC lock is taken, like this:
> https://gist.github.com/ZombineDev/14076777dff7d879d659,
> however this is not currently possible, because the _gc
> variable in gc.proxy is private and by default gc.proxy is not
> part of the include files.
Those two would work better than GC.malloc indeed. A nice thing
is that it seems we don't need synchronization so _gc.gcx.running
would be ideal.
> Since it's really straightforward to expose the information to
> the user, I think this would an easy enhancement.
Perhaps as a getter like GC.isRunning()?
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