bug#61436: Emacs Freezing With Java Files

[Robert Weiner <rswgnu@gmail.com>]

Those are some pretty old regexps in Hyperbole that we have not updated in many years.  Maybe we just need to cross-check them against what is currently in Emacs to resolve this.  I will have a look.  Thanks for tracing through this.

-- rsw

> On Oct 11, 2023, at 8:38 PM, Jens Schmidt <jschmidt4gnu@vodafonemail.de> wrote:
> 
> Hi Alan,
> 
> could you please have a look as well?  This seems to be related to
> cc-mode/java-mode.  New, complete reproducer at the very bottom of this
> mail.
> 
> Thanks!
> 
> Hi Robert & Mats,
> 
> Robert Weiner <rsw@gnu.org> writes:
> 
>> Jens wrote:
>> 
>>> That always freezes Emacs (29 and master) even before it has a chance to
>>> display P1.java.  The freeze happens in function
>>> `c-get-fallback-scan-pos', where the while loop inf-loops, BUT:
>>> 
>>> If you uncomment the line setting `hkey-init' to nil in init.el and
>>> repeat: No freeze.
>> 
>> As you note above, the infinite loop is coming from a Lisp function in
>> Emacs core, not from Hyperbole.  A Hyperbole setting may help you to
>> see a state reached in that function that you otherwise would not, but
>> it is not a Hyperbole bug; it is an unhandled state outside of
>> Hyperbole.
> 
> Well, yes and no.  The next closest culprit seems to be this hook
> addition from function `hui-select-initialize':
> 
>  ;; These hooks let you select C++ and Java methods and classes by
>  ;; double-clicking on the first character of a definition or on its
>  ;; opening or closing brace.  This is all necessary since some
>  ;; programmers don't put their function braces in the first column.
>  (var:add-and-run-hook
>   'java-mode-hook
>   (lambda ()
>     (setq defun-prompt-regexp
>       "^[ \t]*\\(\\(\\(public\\|protected\\|private\\|const\\|abstract\\|synchronized\\|final\\|static\\|threadsafe\\|transient\\|native\\|volatile\\)\\s-+\\)*\\(\\(\\([[a-zA-Z][][_$.a-zA-Z0-9]*[][_$.a-zA-Z0-9]+\\|[[a-zA-Z]\\)\\s-*\\)\\s-+\\)\\)?\\(\\([[a-zA-Z][][_$.a-zA-Z0-9]*\\s-+\\)\\s-*\\)?\\([_a-zA-Z][^][ \t:;.,{}()\x7f=]*\\|\\([_$a-zA-Z][_$.a-zA-Z0-9]*\\)\\)\\s-*\\(([^);{}]*)\\)?\\([] \t]*\\)\\(\\s-*\\<throws\\>\\s-*\\(\\([_$a-zA-Z][_$.a-zA-Z0-9]*\\)[, \t\n\r\f]*\\)+\\)?\\s-*")))
> 
> I (very generally) think that Emacs does not have to grok every regexp
> in every context, but I leave that concrete case for Alan and/or others
> to decide.
> 
>> On Wed, Oct 11, 2023 at 3:29 AM Mats Lidell <mats.lidell@lidells.se> wrote:
>> 
>> Thanks for the report.
> 
> Actually, not mine.  I'm just the messenger who did some root-cause
> analysis.
> 
>> Note: I don't know what P1.java means here. I have picked a java file
>> at random that I had on my machine that is large. Is P1.java a
>> specific file that has been shared earlier?
> 
> The OP has provided that, see below.
> 
>> Hyperbole has its own tracker.
>> 
>> https://debbugs.gnu.org/cgi/pkgreport.cgi?package=hyperbole
> 
> Ok, thanks.  As soon as we know whose bug this is we could forward or
> not.
> 
> 
> Now for the next reproducer (Hyperbole no longer required, but still
> present through its regexp :-):
> 
> - Save the following to ~/tmp/init.el:
> 
> ------------------------- snip -------------------------
> (add-hook
> 'java-mode-hook
> (lambda ()
>   (setq defun-prompt-regexp
>     "^[ \t]*\\(\\(\\(public\\|protected\\|private\\|const\\|abstract\\|synchronized\\|final\\|static\\|threadsafe\\|transient\\|native\\|volatile\\)\\s-+\\)*\\(\\(\\([[a-zA-Z][][_$.a-zA-Z0-9]*[][_$.a-zA-Z0-9]+\\|[[a-zA-Z]\\)\\s-*\\)\\s-+\\)\\)?\\(\\([[a-zA-Z][][_$.a-zA-Z0-9]*\\s-+\\)\\s-*\\)?\\([_a-zA-Z][^][ \t:;.,{}()\x7f=]*\\|\\([_$a-zA-Z][_$.a-zA-Z0-9]*\\)\\)\\s-*\\(([^);{}]*)\\)?\\([] \t]*\\)\\(\\s-*\\<throws\\>\\s-*\\(\\([_$a-zA-Z][_$.a-zA-Z0-9]*\\)[, \t\n\r\f]*\\)+\\)?\\s-*")))
> ------------------------- snip -------------------------
> 
> - Save attachment P1.java from the initial message
> 
>  https://yhetil.org/emacs-bugs/ZPOcahP9yPJ-kLcgipM3-l0jatXJSQWKPfObrlOkIB3dagud85x2DGXGhPpQn1QNqNksVmPIRc1intyW_Cx1Z9ou2vBZ5QLDpLTi_VFVYyg=@protonmail.com/
> 
>  to ~/tmp/P1.java.
> 
> - Start Emacs as
> 
>  ./src/emacs -Q -l ~/tmp/init.el +181 ~/tmp/P1.java
> 
> That always freezes Emacs (29 and master) even before it has a chance to
> display P1.java.  The freeze happens in function
> `c-get-fallback-scan-pos', where the while loop inf-loops.