bug#75322: SAFE_ALLOCA assumed to root Lisp_Objects/SSDATA(string)

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Gerd Möllmann <gerd.moellmann@gmail.com> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>>> Cc: pipcet@protonmail.com,  75322@debbugs.gnu.org
>>> Date: Sun, 05 Jan 2025 21:04:56 +0100
>>> 
>>> Eli Zaretskii <eliz@gnu.org> writes:
>>> 
>>> > How can we possibly make sure this works reliably and safely??  For
>>> > each variable we have in every function, we will need to analyze
>>> > whether the variable is
>>> >
>>> >   . an automatic variable
>>> >   . a static variable that is protected by someone
>>> >   . a global variable that is protected by someone
>>> >   . a result of dereferencing a pointer that is somehow protected
>>> >
>>> > etc. etc., where "protected by someone" means that it is a descendant
>>> > of some staticpro, or of some root, or...
>>> >
>>> > And if we cannot prove to ourselves that one of the above happens,
>>> > then we'd need to force a copy of the variable to be on the stack?
>>> >
>>> > Does this sound practical?
>>> >
>>> > If this is the price of using MPS, and I'm not missing something
>>> > obvious, then it sounds like we should run away from MPS, fast.
>>> > Because we will sooner or later have to rewrite every single line of
>>> > code we ever wrote.
>>> 
>>> I'm bowing out again. It's not worth it.
>>
>> I don't understand why?  I need to understand the implications to be
>> able to make decisions, which are part of my job.  So I ask questions,
>> and I'm grateful for your answers, which clarify the issues for me.
>> That I sometimes sound overwhelmed by the implications shouldn't be
>> held against me, it's just a normal human reaction, nothing more.
>
> I don't hold that against you, that's why I'm trying to answer
> questions, write stuff up, and so on, but for me your reply before this
> one was a leaf node in the thread.
>
>> From my POV: So we're talking about things, you want to make it
> concrete, we land in call_process, I explain why SAFE_NALLOCA is unsafe
> when used with references even with the old GC, you think references are
> on the stack because the parameter args is on stack, and I say no.
>
> Next thing I get is a rant. You don't even say "you're right" or "you're
> wrong", so I don't know for sure if you accept my argumentation or not.
> Instead, you write something that came across here as "unreasonable,
> can't be true, we have to change every line of code, let's run from
> MPS".
>
> What should I reply to that? Nothing of course.
>
>> If I somehow sound impolite, I apologize.
>
> No worries about politeness. It wasn't impolite, and I'm not very
> sensible anyway.

Not being sensible is true also, but s/sensible/sensitive/ :-)