bug#69263: 29.1; emacs freeze with memory swap

[awrhygty]

Eli Zaretskii <eliz@gnu.org> writes:

> tags 69263 moreinfo
> thanks
>
>> From: awrhygty@outlook.com
>> Date: Mon, 19 Feb 2024 14:56:10 +0900
>> 
>> 
>> My PC has 8GB memory and HDD, no SSD.
>> Emacs freezes with the procedure below.
>> 
>> (0) Close all applications.
>> (1) Start task manager.
>>     Confirm disk usage is low and memory usage is about 2GB or less.
>> (2) Start emacs -Q
>> (3) Evaluate the form below
>>       (progn (make-string (* 8000 1000 1000) 0)
>>              (kill-emacs))
>> (4) Memory usage increases and then decreases in ten seconds.
>> (5) Disk usage keep 100% active for a few minutes.
>> (6) Application window of emacs keep alive and emacs process name is
>>     displayed in the process tab of task manager.
>>     (At least 10 hours, I waited.)
>
> I don't have a 8GB 64-bit Windows system to try this, and the results
> are likely to be dependent on the intimate details of the Virtual
> Memory setup on that system.
>
> So if you want to help us understand what happens in the strange case
> where a Lisp program creates a 8GB Lisp string, and clear it all, on a
> 8GB MS-Windows system, please attach GDB to Emacs after running the
> above recipe, and produce a backtrace that can be used to try to
> figure out what happens.  (I hope that your Emacs binary is not
> stripped of debugging symbols, because if it's stripped, GDB will not
> tell anything useful.)
>
> Thanks.

I installed MSYS2 and GDB for this.
At first, I tried to attach with emacs PID.
GDB says "Can't attach to process 1099".
So I tried with WINPID.
I am not sure it is a correct parameter.

Here is a log within MSYS2 shell:
$ ps
      PID    PPID    PGID     WINPID   TTY         UID    STIME COMMAND
     1051       1    1051       3940  ?         197609 20:56:49 /usr/bin/mintty
     1205    1052    1205       9776  pty0      197609 22:26:16 /usr/bin/ps
     1052    1051    1052      11328  pty0      197609 20:56:49 /usr/bin/bash
     1099    1052    1099       1384  pty0      197609 21:10:57 
/c/Emacs/emacs-29.1/bin/emacs
$ /mingw64/bin/gdb
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Type "show copying" and "show warranty" for details.
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(gdb) attach 1384
Attaching to process 1384
[New Thread 1384.0xbbc]
[New Thread 1384.0xbe0]
[New Thread 1384.0x2bc0]
[New Thread 1384.0x2cc4]
[New Thread 1384.0x14a4]
Reading symbols from C:\Emacs\emacs-29.1\bin\emacs.exe...
(gdb) bt full
#0  0x00007ffa73710b11 in ntdll!DbgBreakPoint () from 
C:\WINDOWS\SYSTEM32\ntdll.dll
No symbol table info available.
#1  0x00007ffa7373ca0e in ntdll!DbgUiRemoteBreakin () from 
C:\WINDOWS\SYSTEM32\ntdll.dll
No symbol table info available.
#2  0x00007ffa72237344 in KERNEL32!BaseThreadInitThunk () from 
C:\WINDOWS\System32\kernel32.dll
No symbol table info available.
#3  0x00007ffa736c26b1 in ntdll!RtlUserThreadStart () from 
C:\WINDOWS\SYSTEM32\ntdll.dll
No symbol table info available.
#4  0x0000000000000000 in ?? ()
No symbol table info available.
(gdb) detach
Detaching from program: C:\Emacs\emacs-29.1\bin\emacs.exe, process 1384
[Inferior 1 (process 1384) detached]
(gdb) exit