bug#39482: 26.3; set-fontset-font with emacs charset does not work correctly

[ynyaaa@gmail.com]

I tried to setup fontset to display a same character with different
'charset text property using different fonts.

(let* ((base "Courier New")
       (size 18)
       (un-spec "SimHei")
       (tc-spec '("MingLiU"   . "big5"))
       (sc-spec '("SimSun"    . "gb2312.1980"))
       (jp-spec '("MS Mincho" . "jisx0208"))
       (kr-spec '("BatangChe" . "ksc5601.1987"))
       )
  (set-charset-priority 'ascii)
  (set-frame-font (format "%s-%g" base size t))
  (set-frame-size nil 80 28)
  (set-fontset-font t '(#x80 . #x10FFFF) un-spec)
  (set-fontset-font t 'chinese-gb2312    sc-spec nil 'append)
  (set-fontset-font t 'big5              tc-spec nil 'append)
  (set-fontset-font t 'japanese-jisx0208 jp-spec nil 'append)
  (set-fontset-font t 'korean-ksc5601    kr-spec nil 'append)
  )

But some characters are not displayed with specified fonts.

CJK Ideographs are displayed as intended:
M-x list-charset-chars RET unicode-bmp RET
  CJK Ideographs are displayed with SimHei.
M-x list-charset-chars RET big5 RET
  CJK Ideographs are displayed with MingLiU.

CJK Ideographs are not displayed as intended:
M-x list-charset-chars RET chinese-gb2312 RET
  CJK Ideographs are displayed with SimSun except for
    啊爱罢帮逼彼蔽庇辟辩...(and more). They are displayed with SimHei.
M-x list-charset-chars RET japanese-jisx0208 RET
  CJK Ideographs are displayed with "MS Mincho" except for
    亜愛挨芦按偉椅為稲蔭...(and more). They are displayed with SimHei.
M-x list-charset-chars RET korean-ksc5601 RET
  CJK Ideographs are displayed with SimHei, not the intended font.
  CJK Compatibility Ideographs are not displayed.


In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29 built on CIRROCUMULUS
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor 'Microsoft Corp.', version 10.0.18363
Recent messages:

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS THREADS LCMS2

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-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
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils term/bobcat elec-pair
time-date mule-util japan-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type 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 elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame 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 charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files 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
emacs)

Memory information:
((conses 16 99563 9820)
 (symbols 48 20238 1)
 (miscs 40 38 143)
 (strings 32 29830 1170)
 (string-bytes 1 767316)
 (vectors 16 24983)
 (vector-slots 8 698705 17442)
 (floats 8 51 78)
 (intervals 56 260 7)
 (buffers 992 12))