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Re: Fix to long-standing crashes in GC
From: |
Stefan Monnier |
Subject: |
Re: Fix to long-standing crashes in GC |
Date: |
21 May 2004 18:58:07 -0400 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50 |
> Marking a misc object sets the mark bit in it. If this supposed misc
> object isn't really other data, that will destroy the other data
> there.
misc_live_p is supposed to make sure this never happens.
> Likewise for symbols. With conservative stack marking, it
> would seem that using a mark bit inside an object is a bug, unless
> mark_object can first verify the object is real.
mark_object is only called after checking that the presumed pointer does
point to a live object of the expected type.
> mark_buffer seems to have a similar problem.
And the same solution is applied.
> I think GETMARKBIT has a similar problem, in that it assumes
> that the cons or float is contained in a real cons block or a real
> float block. It finds the address of that block by address
> calculations. If it found random data that points to a supposed
> cons cell in the wrong place, the address calculations will give
> an address that doesn't really correspond to a cons block.
That's what find_mem is for: to make sure it's indeed one of our cons
blocks or float block (and which of the two).
> When it tries to find the mark bits of that block, it can crash
> on an invalid pointer, or even find a valid-looking pointer to
> other data and garble it.
Only if there's a bug in the mem_find code.
Stefan
- Re: Fix to long-standing crashes in GC, (continued)
- Re: Fix to long-standing crashes in GC, Stefan Monnier, 2004/05/23
- Re: Fix to long-standing crashes in GC, Richard Stallman, 2004/05/23
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/24
- Re: Fix to long-standing crashes in GC, Stefan Monnier, 2004/05/28
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/29
- Re: Fix to long-standing crashes in GC, Stefan Monnier, 2004/05/29
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/29
- Re: Fix to long-standing crashes in GC, Stefan Monnier, 2004/05/30
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/31
- Re: Fix to long-standing crashes in GC, Richard Stallman, 2004/05/20
- Re: Fix to long-standing crashes in GC,
Stefan Monnier <=
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/19
- Re: Fix to long-standing crashes in GC, Stefan Monnier, 2004/05/19
- Re: Fix to long-standing crashes in GC, Kim F. Storm, 2004/05/19
- Re: Fix to long-standing crashes in GC, Richard Stallman, 2004/05/20
Re: Fix to long-standing crashes in GC, Robert Anderson, 2004/05/13