-me and -mgchar do not play well together

[subrook]

This troff input:

.warn +w
Hello.

when processed with both the -me and -mgchar options, produces the following on stderr:

troff: no such register ?H; line 1, file <standard input>; page 1
@h 
troff: no such register ?C; line 1, file <standard input>; page 1
@h 
troff: |4: no such request; line 1, file <standard input>; page 1
@h 
troff: |5: no such request; line 1, file <standard input>; page 1
@h 
troff: |6: no such request; line 1, file <standard input>; page 1
@h 
troff: |7: no such request; line 1, file <standard input>; page 1
@h 
troff: @m: no such request; line 1, file <standard input>; page 1
@h 
troff: illegal number, char B; line 1, file <standard input>; page 1
sz @t @h 
troff: |1: no such request; line 1, file <standard input>; page 1
$h @t @h 
troff: no such register ?n; line 1, file <standard input>; page 1
@h 
troff: no such register ?s; line 1, file <standard input>; page 1
@h 
troff: no such register ?o; line 1, file <standard input>; page 1
@n @h 
troff: no such register ?T; line 1, file <standard input>; page 1
@n @h 
troff: no such register ?a; line 1, file <standard input>; page 1
@n @h 
troff: no such register ?w; line 1, file <standard input>; page 1
@n @h 
troff: $H: no such request; line 1, file <standard input>; page 1
@n @h 
troff: no such register ?b; line 2, file <standard input>; page 1
@f 
troff: illegal number, char B; line 2, file <standard input>; page 1
sz @t @e @f 
troff: |z: no such request; line 2, file <standard input>; page 1
$f @t @e @f 
troff: |3: no such request; line 2, file <standard input>; page 1
$f @t @e @f 
troff: bp: no such request; line 2, file <standard input>; page 1
@e @f 
troff: @m: no such request; line 2, file <standard input>; page 1
@f