--- src/test/encodings/expected/gb18030.out	2025-09-11 14:10:18.511609698 +0700
+++ patch.out	2025-09-11 14:12:42.001008191 +0700
@@ -1,62 +1,3 @@
--- Enumerate all valid GB18030 byte sequences. Not all of these encode an actual character, but
--- this enumerates everything that's accepted by the verification function.
-create function most_gb18030() returns setof bytea language plpgsql as
-$$
-declare
-  byte1 integer;
-  byte2 integer;
-  byte3 integer;
-  byte4 integer;
-begin
-  -- 4-byte encoded values have:
-  -- byte1 in range 0x81-0xfe
-  -- byte2 in range 0x30-0x39
-  -- byte3 in range 0x81-0xfe
-  -- byte2 in range 0x30-0x39
-  for byte1 in hex('81') .. hex('fe') loop
-
-     -- Skip some values that are not interesting, to keep the table
-     -- manageable.
-     if (byte1 >= hex('85') and byte1 <= hex('8e')) or
-        (byte1 >= hex('e4') and byte1 <= hex('fd')) then
-       continue;
-     end if;
-
-     -- skip more values
-     if (byte1 >= hex('a1') and byte1 <= hex('d0')) then
-       continue;
-     end if;
-
-     for byte2 in hex('30') .. hex('39') loop
-      for byte3 in hex('81') .. hex('fe') loop
-          for byte4 in hex('30') .. hex('39') loop
-              return next b(byte1, byte2, byte3, byte4);
-          end loop;
-	  --
-      end loop;
-    end loop;
-  end loop;
-
-  -- 2-byte encoded values have:
-  -- byte1 in range 0x81-0xfe
-  -- byte2 in range 0x40-0x7e or 0x80-0xfe
-  for byte1 in hex('81') .. hex('fe') loop
-    for byte2 in hex('40') .. hex('7e') loop
-      return next b(byte1, byte2);
-    end loop;
-
-    for byte2 in hex('80') .. hex('fe') loop
-      return next b(byte1, byte2);
-    end loop;
-  end loop;
-
-  -- ASCII
-  for byte1 in hex('01')..hex('7f') loop
-    return next b(byte1);
-  end loop;
-end;
-$$;
-select gb18030_char, convert_roundtrip(gb18030_char, 'gb18030', 'utf8') from most_gb18030() as gb18030_char;
  gb18030_char |                                              convert_roundtrip                                              
 --------------+-------------------------------------------------------------------------------------------------------------
  \x81308130   | \xc280
@@ -7516,7 +7457,7 @@
  \x8135f434   | \xe1b8bc
  \x8135f435   | \xe1b8bd
  \x8135f436   | \xe1b8be
- \x8135f437   | \xe1b8bf
+ \x8135f437   | \xee9f87
  \x8135f438   | \xe1b980
  \x8135f439   | \xe1b981
  \x8135f530   | \xe1b982
@@ -19116,14 +19057,14 @@
  \x82359034   | \xe9beb1
  \x82359035   | \xe9beb2
  \x82359036   | \xe9beb3
- \x82359037   | \xe9beb4
- \x82359038   | \xe9beb5
- \x82359039   | \xe9beb6
- \x82359130   | \xe9beb7
- \x82359131   | \xe9beb8
- \x82359132   | \xe9beb9
- \x82359133   | \xe9beba
- \x82359134   | \xe9bebb
+ \x82359037   | \xe9beb4, roundtripped to \xfe59
+ \x82359038   | \xe9beb5, roundtripped to \xfe61
+ \x82359039   | \xe9beb6, roundtripped to \xfe66
+ \x82359130   | \xe9beb7, roundtripped to \xfe67
+ \x82359131   | \xe9beb8, roundtripped to \xfe6d
+ \x82359132   | \xe9beb9, roundtripped to \xfe7e
+ \x82359133   | \xe9beba, roundtripped to \xfe90
+ \x82359134   | \xe9bebb, roundtripped to \xfea0
  \x82359135   | \xe9bebc
  \x82359136   | \xe9bebd
  \x82359137   | \xe9bebe
@@ -39135,16 +39076,16 @@
  \x84318233   | \xefb88d
  \x84318234   | \xefb88e
  \x84318235   | \xefb88f
- \x84318236   | \xefb890
- \x84318237   | \xefb891
- \x84318238   | \xefb892
- \x84318239   | \xefb893
- \x84318330   | \xefb894
- \x84318331   | \xefb895
- \x84318332   | \xefb896
- \x84318333   | \xefb897
- \x84318334   | \xefb898
- \x84318335   | \xefb899
+ \x84318236   | \xefb890, roundtripped to \xa6d9
+ \x84318237   | \xefb891, roundtripped to \xa6db
+ \x84318238   | \xefb892, roundtripped to \xa6da
+ \x84318239   | \xefb893, roundtripped to \xa6dc
+ \x84318330   | \xefb894, roundtripped to \xa6dd
+ \x84318331   | \xefb895, roundtripped to \xa6de
+ \x84318332   | \xefb896, roundtripped to \xa6df
+ \x84318333   | \xefb897, roundtripped to \xa6ec
+ \x84318334   | \xefb898, roundtripped to \xa6ed
+ \x84318335   | \xefb899, roundtripped to \xa6f3
  \x84318336   | \xefb89a
  \x84318337   | \xefb89b
  \x84318338   | \xefb89c
@@ -535814,7 +535755,7 @@
  \xa39d       | \xee97a2
  \xa39e       | \xee97a3
  \xa39f       | \xee97a4
- \xa3a0       | \xee97a5
+ \xa3a0       | character with byte sequence 0xa3 0xa0 in encoding "GB18030" has no equivalent in encoding "UTF8"
  \xa3a1       | \xefbc81
  \xa3a2       | \xefbc82
  \xa3a3       | \xefbc83
@@ -536441,13 +536382,13 @@
  \xa6d6       | \xcf87
  \xa6d7       | \xcf88
  \xa6d8       | \xcf89
- \xa6d9       | \xee9e8d
- \xa6da       | \xee9e8e
- \xa6db       | \xee9e8f
- \xa6dc       | \xee9e90
- \xa6dd       | \xee9e91
- \xa6de       | \xee9e92
- \xa6df       | \xee9e93
+ \xa6d9       | \xefb890
+ \xa6da       | \xefb892
+ \xa6db       | \xefb891
+ \xa6dc       | \xefb893
+ \xa6dd       | \xefb894
+ \xa6de       | \xefb895
+ \xa6df       | \xefb896
  \xa6e0       | \xefb8b5
  \xa6e1       | \xefb8b6
  \xa6e2       | \xefb8b9
@@ -536460,14 +536401,14 @@
  \xa6e9       | \xefb982
  \xa6ea       | \xefb983
  \xa6eb       | \xefb984
- \xa6ec       | \xee9e94
- \xa6ed       | \xee9e95
+ \xa6ec       | \xefb897
+ \xa6ed       | \xefb898
  \xa6ee       | \xefb8bb
  \xa6ef       | \xefb8bc
  \xa6f0       | \xefb8b7
  \xa6f1       | \xefb8b8
  \xa6f2       | \xefb8b1
- \xa6f3       | \xee9e96
+ \xa6f3       | \xefb899
  \xa6f4       | \xefb8b3
  \xa6f5       | \xefb8b4
  \xa6f6       | \xee9e97
@@ -536792,7 +536733,7 @@
  \xa8b9       | \xc3bc
  \xa8ba       | \xc3aa
  \xa8bb       | \xc991
- \xa8bc       | \xee9f87
+ \xa8bc       | \xe1b8bf
  \xa8bd       | \xc584
  \xa8be       | \xc588
  \xa8bf       | \xc7b9
@@ -553034,7 +552975,7 @@
  \xfe56       | \xe39187
  \xfe57       | \xe2ba88
  \xfe58       | \xe2ba8b
- \xfe59       | \xeea09e
+ \xfe59       | \xe9beb4
  \xfe5a       | \xe3969e
  \xfe5b       | \xe3989a
  \xfe5c       | \xe3988e
@@ -553042,19 +552983,19 @@
  \xfe5e       | \xe2ba97
  \xfe5f       | \xe3a5ae
  \xfe60       | \xe3a498
- \xfe61       | \xeea0a6
+ \xfe61       | \xe9beb5
  \xfe62       | \xe3a78f
  \xfe63       | \xe3a79f
  \xfe64       | \xe3a9b3
  \xfe65       | \xe3a790
- \xfe66       | \xeea0ab
- \xfe67       | \xeea0ac
+ \xfe66       | \xe9beb6
+ \xfe67       | \xe9beb7
  \xfe68       | \xe3ad8e
  \xfe69       | \xe3b1ae
  \xfe6a       | \xe3b3a0
  \xfe6b       | \xe2baa7
  \xfe6c       | \xeea0b1
- \xfe6d       | \xeea0b2
+ \xfe6d       | \xe9beb8
  \xfe6e       | \xe2baaa
  \xfe6f       | \xe48196
  \xfe70       | \xe4859f
@@ -553071,7 +553012,7 @@
  \xfe7b       | \xe49396
  \xfe7c       | \xe499a1
  \xfe7d       | \xe4998c
- \xfe7e       | \xeea183
+ \xfe7e       | \xe9beb9
  \xfe80       | \xe49ca3
  \xfe81       | \xe49ca9
  \xfe82       | \xe49dbc
@@ -553088,7 +553029,7 @@
  \xfe8d       | \xe4a69b
  \xfe8e       | \xe4a6b7
  \xfe8f       | \xe4a6b6
- \xfe90       | \xeea194
+ \xfe90       | \xe9beba
  \xfe91       | \xeea195
  \xfe92       | \xe4b2a3
  \xfe93       | \xe4b29f
@@ -553104,7 +553045,7 @@
  \xfe9d       | \xe4b498
  \xfe9e       | \xe4b499
  \xfe9f       | \xe4b6ae
- \xfea0       | \xeea1a4
+ \xfea0       | \xe9bebb
  \xfea1       | \xee91a8
  \xfea2       | \xee91a9
  \xfea3       | \xee91aa