bug#62450: 29.0.60; Skip failing tests on Cygwin with native compilation

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 26 Mar 2023 10:15:17 -0400
> Cc: 62450-done@debbugs.gnu.org
> From: Ken Brown <kbrown@cornell.edu>
> 
> On 3/26/2023 12:44 AM, Eli Zaretskii wrote:
> 
> > (I do wonder whether this is a good idea in the long run.  Native
> > compilation is here to stay, so avoiding its testing for Cygwin might
> > not be the best solution.  The PROBLEMS entry seems to imply that
> > relatively simple measures, which the test suite could take, could
> > avoid the fork failures, so my recommendation would be to try to find
> > a better fix in the future, albeit not in Emacs 29.)
> 
> I agree, and I hope I can do it.

Great, thanks.

> By the way, I've been experimenting with building the .eln files
> with ASLR enabled, via the following:
> 
> --- a/lisp/emacs-lisp/comp.el
> +++ b/lisp/emacs-lisp/comp.el
> @@ -186,8 +186,9 @@ native-comp-compiler-options
>     :type '(repeat string)
>     :version "28.1")
> 
> -(defcustom native-comp-driver-options (when (eq system-type 'darwin)
> -                                        '("-Wl,-w"))
> +(defcustom native-comp-driver-options
> +  (cond ((eq system-type 'darwin) '("-Wl,-w"))
> +        ((eq system-type 'cygwin) '("-Wl,-dynamicbase")))
>     "Options passed verbatim to the native compiler's back-end driver.
>   Note that not all options are meaningful; typically only the options
>   affecting the assembler and linker are likely to be useful.
> 
> I've been building and running Emacs like this for a couple months and 
> not doing any rebasing, and I haven't seen a single fork failure outside 
> of the test suite.  So this might be the way to handle the problem in 
> the long run.

Feel free to install the above on master.

> But I still hope to figure out what's different about native
> compilation in the test suite.

You mean, why the fork fails?  I thought the PROBLEMS entry explains
that?