In src/backend/utils/adt/varlena.c,
766 line must be exits in block of 'else if (elm >1)' too.
Because, strpos() function make a wrong result in multibyte string.
line 796
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ps1 = p1 = (pg_wchar *) palloc((len1 + 1) * sizeof(pg_wchar));
(void) pg_mb2wchar_with_len((unsigned char *) VARDATA(t1), p1, len1);
len1 = pg_wchar_strlen(p1);
ps2 = p2 = (pg_wchar *) palloc((len2 + 1) * sizeof(pg_wchar));
(void) pg_mb2wchar_with_len((unsigned char *) VARDATA(t2), p2, len2);
len2 = pg_wchar_strlen(p2);
/*** recalculate px ****/
px = (len1 - len2);
for (p = 0; p <= px; p++)