Re: [Emacs-diffs] trunk r117912: Minor improvements to new stack-allocated Lisp objects.

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> For example, build_desired_tool_bar_string has a loop, each iteration
>> of which creates temporaries; here local_list4 could exhaust the
>> stack whereas scoped_list4 is fine, and trunk bzr 117912 fixed that
>> by replacing local_list4 with scoped_list4.

Yuck!

> SAFE_ALLOCA and friends has exactly the same problems, and I don't see
> the way to make it absolutely safe with an existing implementations of
> alloca.

We don't need it to be absolutely safe (it's a given that using pointers
into stack-allocated objects is generally unsafe, unless we use some
code analysis to try and enforce some discipline).

But the rules that have to be followed need to be *very* clear and
stated in the most obvious (or in your face) place.

[ And even if we do that, someone unfamiliar with those rules will come
  up and modify "unrelated" code which end up breaking them.  ]


        Stefan