Re: SIGPROF + SIGCHLD and igc

[Helmut Eller <eller.helmut@gmail.com>]

On Tue, Dec 24 2024, Gerd Möllmann wrote:

[...]
>>> - Lisp allocation in signal handlers cannot exist because alloc.c is not
>>>   reentrant which means we would crash with the old GC. We don't need
>>>   anything extra for that in igc.
[...]
> BTW, do you agree with my analysis that Lisp allocations can't possibly
> exist in signal handlers today?

I don't know alloc.c well enough to make a judgment.  This comment for
XMALLOC_BLOCK_INPUT_CHECK seems to say that signal handlers used to
allocate but no longer do:

  If compiled with XMALLOC_BLOCK_INPUT_CHECK, define a symbol
  BLOCK_INPUT_IN_MEMORY_ALLOCATORS that is visible to the debugger.
  If that variable is set, block input while in one of Emacs's memory
  allocation functions.  There should be no need for this debugging
  option, since signal handlers do not allocate memory, but Emacs
  formerly allocated memory in signal handlers and this compile-time
  option remains as a way to help debug the issue should it rear its
  ugly head again.  */

Helmut