First of all, I'm on Windows 10, using the MINGW64 MSYS2 environment, so
this issue might be specific to MinGW. Note: While I'm using a UCRT
build of Emacs to generate this report, the problem is present in the
MinGW GCC build as well. Emacs has some weird behaviour regarding
subprocess handling (?) when compiled with
"-D_FORTIFY_SOURCE=1". Setting the value to 2 causes the same issue, I
haven't tested setting it to 3. I believe this is the why the MSYS2
Emacs builds have been broken for a while now:

https://github.com/msys2/MINGW-packages/issues/16190
https://github.com/msys2/MINGW-packages/issues/16375
https://github.com/msys2/MINGW-packages/issues/16413

I've managed to reproduce the issue when building from the emacs
sources as follows:

git clone https://git.savannah.gnu.org/git/emacs.git
cd emacs
git checkout emacs-28.2
./autogen.sh
export CFLAGS='-g3 -O2 -gdwarf-2 -Wp,-D_FORTIFY_SOURCE=1'
./configure
make

"-g3 -O2 -gdwarf-2" were the default compilation options. The build
terminates fine but the executable has problems. Executing "dir" via
async-shell-command doesn't terminate properly, for example:

./src/emacs -Q --eval '(async-shell-command "dir")'

Trying to close the window results in Emacs saying there are active
processes, which there shouldn't be. Other symptoms are described in the
linked Github issues.

In the example above, I built Emacs from the emacs-28.2 tag, but I also
managed to reproduce the issue in the emacs-28, emacs-29 and master
branches.



In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
of 2023-05-27 built on ZUERILL
Repository revision: f31980c83aee3840ee90688447198a37a14f7aaf
Repository branch: emacs-28.2
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.2965)

Configured using:
'configure --prefix=/ucrt64 --host=x86_64-w64-mingw32
--build=x86_64-w64-mingw32 --with-modules --without-dbus
--without-compress-install --with-native-compilation
'CFLAGS=-march=nocona -msahf -mtune=generic -O2 -pipe
-fstack-protector-strong' CPPFLAGS=-D__USE_MINGW_ANSI_STDIO=1
'LDFLAGS=-pipe -lpthread''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB

Important settings:
  value of $LANG: en_GB
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
  display-line-numbers-mode: t
  override-global-mode: t
  delete-selection-mode: t
  tabbar-mwheel-mode: t
  tabbar-mode: t
  global-so-long-mode: t
  global-flycheck-mode: t
  flycheck-mode: t
  cua-mode: t
  company-tng-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
~/.lisp/load/vhdl-mode hides c:/msys64/ucrt64/share/emacs/28.2/lisp/progmodes/vhdl-mode

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils display-line-numbers cl-extra
use-package use-package-ensure use-package-delight use-package-diminish
use-package-bind-key bind-key use-package-core server delsel tabbar
easy-mmode grep compile text-property-search comint ring so-long
flycheck ansi-color find-func help-mode rx dash cua-base company-tng
company edmacro kmacro pcase cus-load tex-site info package browse-url
url url-proxy url-privacy url-expand url-methods url-history url-cookie
url-domsuf url-util mailcap url-handlers url-parse auth-source cl-seq
eieio eieio-core cl-macs eieio-loaddefs password-cache json subr-x map
url-vars seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel dos-w32 ls-lisp disp-table
term/w32-win w32-win w32-vars term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads w32notify w32 lcms2 multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 161207 53896)
(symbols 48 13207 112)
(strings 32 43518 8562)
(string-bytes 1 1529452)
(vectors 16 23546)
(vector-slots 8 437343 90008)
(floats 8 73 206)
(intervals 56 299 290)
(buffers 992 11))