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Re: Ruby testsuite failures because of pointer mangling on 32-bit ARM?

From: David Miller <>
Date: Thu, 12 Dec 2013 12:14:41 -0500 (EST)

> From: "Carlos O'Donell" <>
> Date: Thu, 12 Dec 2013 00:55:01 -0500
>> It treats the jmp_buf as an array of VALUE sized pointers that
>> it can examine to determine if there are pointers to the heap.
> Sounds similar to what any other garbage collector will do, scan
> the processes address space looking for pointers.
> I'm pretty sure Boehm-GC does something similar, although perhaps
> it scans the entire process stack from the point in which it is
> called instead of using jmpbuf's to delineate spans of stack
> areas like Ruby does.

And, indirectly, realize that even a straight stack scan is going
to potentially break if you start mangling pointers in jmpbuf.

Consider the case where if the jmpbuf is on the processes stack, and
normally it would get scanned by GC and the pointer followed to find
memory references, and now that would not work because the pointer is

I think all of these schemes are legitimate and erroneously broken
by pointer mangling.

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