[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#41357: 28.0.50; GC may miss to mark calle safe register content
From: |
Paul Eggert |
Subject: |
bug#41357: 28.0.50; GC may miss to mark calle safe register content |
Date: |
Sun, 17 May 2020 12:05:25 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 |
On 5/17/20 10:24 AM, Eli Zaretskii wrote:
> I struggle to see
> how a Lisp object could appear in a register without leaving any trace
> on the stack
Quite easily. It happens all the time. If I do something like this:
Lisp_Object a = Fcons (b, c);
f (x, y);
return a;
The compiler might put 'a' into a callee-save register R, which means that while
f is running there's no trace of 'a' on the stack (unless f's code itself
decides to use R for whatever reason, but let's suppose it doesn't). This
situation can persist even if f calls g which calls h which calls the garbage
collector, and the garbage collector will then think the cons is garbage even
though it's not.
The proposed fix is harmless except it may execute a handful more instructions
per GC. So the cost of applying the fix is tiny, whereas the potential
reliability benefit is large.
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, (continued)
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Paul Eggert, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Andrea Corallo, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Eli Zaretskii, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Andrea Corallo, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Eli Zaretskii, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Andrea Corallo, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Eli Zaretskii, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Andrea Corallo, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Paul Eggert, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Eli Zaretskii, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content,
Paul Eggert <=
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Eli Zaretskii, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Andrea Corallo, 2020/05/17
- bug#41357: 28.0.50; GC may miss to mark calle safe register content, Paul Eggert, 2020/05/17
bug#41357: 28.0.50; GC may miss to mark calle safe register content, Tom Tromey, 2020/05/24