try to fix #68

source/texk/web2c/ptexdir/ptex-base.ch

@@ -324,6 +324,13 @@ else
   wterm(')');
 @z
 
+@x
+@d max_halfword==@"FFFFFFF {largest allowable value in a |halfword|}
+@y
+@d max_halfword==@"FFFFFFF {largest allowable value in a |halfword|}
+@d max_cjk_val=@"10000
+@z
+
 @x [8.111] l.2436 - pTeX: check hi/ho
   (mem_top+sup_main_memory>=max_halfword) then bad:=14;
 @y
@@ -2536,7 +2543,7 @@ if (cur_cmd=kanji)or(cur_cmd=kana)or(cur_cmd=other_kchar) then
   begin m:=cur_cmd; n:=cur_chr;
   end
 else if (cur_cmd>active_char)or(cur_chr>255) then
-  begin m:=relax; n:=256;
+  begin m:=relax; n:=max_cjk_val;
   end
 else  begin m:=cur_cmd; n:=cur_chr;
   end;
@@ -2545,7 +2552,7 @@ if (cur_cmd=kanji)or(cur_cmd=kana)or(cur_cmd=other_kchar) then
   begin cur_cmd:=cur_cmd;
   end {dummy}
 else if (cur_cmd>active_char)or(cur_chr>255) then
-  begin cur_cmd:=relax; cur_chr:=256;
+  begin cur_cmd:=relax; cur_chr:=max_cjk_val;
   end;
 @z
 

source/texk/web2c/uptexdir/tests/test_if.tex

@@ -0,0 +1,20 @@
+\kcatcode`あ=18
+\def\xA{あ}\let\yA=あ
+\kcatcode`あ=17
+
+\message{\ifcat あ\xA Y\else N\fi}
+\message{\ifcat あ\yA Y\else N\fi}
+
+\ifx\ucs\undefined\else
+  \kcatcode"100=16
+  \message{upTeX}
+  \def\xA{Ā}% U+0100
+  \def\xB{ā}% U+0101
+  \message{\if   \xA\relax Y\else N\fi}
+  \message{\if   \xB\relax Y\else N\fi}
+  \message{\ifcat\xA\relax Y\else N\fi}
+  \message{\ifcat\xB\relax Y\else N\fi}
+\fi
+\end
+
+

source/texk/web2c/uptexdir/uptex-m.ch

@@ -142,6 +142,7 @@ if (kcode_pos=1)or((kcode_pos>=@'11)and(kcode_pos<=@'12))
 @d max_quarterword=255 {largest allowable value in a |quarterword|}
 @d min_halfword==-@"FFFFFFF {smallest allowable value in a |halfword|}
 @d max_halfword==@"FFFFFFF {largest allowable value in a |halfword|}
+@d max_cjk_val=@"10000
 @y
 @d min_quarterword=0 {smallest allowable value in a |quarterword|}
 @d max_quarterword=@"FFFF {largest allowable value in a |quarterword|}