EXC_BAD_ACCESS on older iOS devices for first launch

[leisim]

Hey,

I get the following error for older iPhones like the iPhone SE. It only happens when the app is launched for the first time. Any idea how to fix it?

[erthink]

I think it's some kind of defect in older versions of iOS or incompatibility with standards like POSIX.
Please set breakpoing above to the rc = alloc_page_buf(); and step into the mdbx_memalign_alloc().
This will allow you to understand exactly which function is called on the problematic OS and search for information about this trouble and methods to work around it.

[leisim]

Thanks! I will try that. But the device runs the latest iOS 15 🤔

[leisim]

This is what I get. me_pbuf already has a value.

[erthink]

I found potential bug that could trigger such access violation in some cases.
Please check out the current devel branch.

If the problem persists, then set the breakpoint inside the mdbx_memalign_alloc(). So you will catch the buffer allocation.

[leisim]

me_pbuf is still not 0 so mdbx_memalign_alloc is not called.

Could this code be problematic?
https://github.com/isar/isar-core/blob/8c3c2dd83f125501ac859e0b01ca39ae80f2f692/src/mdbx/env.rs#L35-L50

It is needed because iOS only grants a limited amount of virtual memory.

Also weird that it only affects the very first time the app is opened...

[leisim]

Oh, it is actually called but in the previous iteration of my loop.

[erthink]

Could this code be problematic? https://github.com/isar/isar-core/blob/8c3c2dd83f125501ac859e0b01ca39ae80f2f692/src/mdbx/env.rs#L35-L50

Yes.
This is a really strange solution, and the such case was overlooked.
However, I should fix this, i.e. make libmdbx code more idempotence.

[erthink]

@leisim, Please check this and close issue on success.
Thank you for reporting.

[leisim]

@erthink It works! Thanks a lot. I know it is a bit unusual but mai.ru also uses this method in their app. I didn't find a better solution.