[bug #68256] [troff] `.bd S 3 3` doesn't work

Deri James <[email protected]> Thu, 2 Jul 2026 06:49:13 -0400 (EDT)
Newsgroups	gmane.comp.printing.groff.bugs
Message-ID	<[email protected]>
Follow-up Comment #22, bug #68256 (group groff):

Self follow up!

I grabbed "https://github.com/n-t-roff/Plan9_troff.git" which compiled with
warnings using fairly old gcc on Mageia (failed to compile on up-to-date
Debian). tr2post segv's, however troff does produce grout, the only device is
utf.

Things to note:-

Since the device is utf, all unicode characters are in the "current" font, so
using \(mu does not switch to Symbol font since it assumes it is present in
the current text font. This means the conditional form of .bd is obsolete
because it will never switch to a Special font.

Using this script:-

[derij@pip Plan9_troff (master)]$ cat bdtest.ms
.bd S 3 4
\fB8\(mu8\fR

The following grout produced:-

troff/nroff version March 11, 1994
invoke request ds
invoke request ds
invoke request bd
x T utf
x res 720 1 1
x init
V0
p1
x font 1 R
x font 2 I
x font 3 B
x font 4 BI
x font 5 CW
x font 6 H
x font 7 HI
x font 8 HB
x font 9 S1
x font 10 S
s10
f3
H720
V120
c8
h50Cmu
558n120 0
x trailer
V7920
x stop

There is no "bolding" and no switch to font S (f10).

Using gdb om the same input:-

Starting program: /usr/local/p9roff/bin/troff -d -t255 bdtest.ms
Missing separate debuginfos, use: debuginfo-install glibc-2.36-59.mga9.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
troff/nroff version March 11, 1994
invoke request ds
invoke request ds
invoke request bd

Breakpoint 1, casebd () at t6.c:785
785             if (!TROFF) {
(gdb) n
789             zapwcache(0);
(gdb)
790             j = k = 0;
(gdb)
792             if (skip() || !(i = getrq()) || (j = findft(i)) == -1) {
(gdb)
798             if (j == smnt) {
(gdb)
802             if (k) {
(gdb)
806     bd1:
(gdb)
807             skip();
(gdb)
808             noscale++;
(gdb)
809             bdtab[j] = atoi0();
(gdb)
810             noscale = 0;
(gdb) p bdtab
$1 = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0 <repeats 89 times>}

NOTE: bdtab[10] (font S) is holding the second param.

(gdb) n
811     }
(gdb)
control (a=6553698, b=1) at n1.c:341
341             return(0);
(gdb) s
342     }
(gdb)
main (argc=1, argv=0x7fffffffd6d0) at n1.c:209
209                     flushi();
(gdb) s
flushi () at n1.c:854

NOTE: 'flushi' discards up to new line

854             if (nflush)
(gdb)
856             ch = 0;
(gdb)
857             copyf++;
(gdb)
858             while (!nlflg) {
(gdb)
859                     if (donef && frame == stk)
(gdb)
861                     getch();
(gdb)
getch () at n1.c:411
411             if (ch) {
(gdb)
419             if (nlflg)
(gdb)
421             i = getch0();
(gdb)
getch0 () at n1.c:677
677             if (pbp > lastpbp)
(gdb) n
679             else if (ip) {
(gdb)
692                     if (donef || ndone)
(gdb)
695                             if (nfo < 0)
(gdb)
697                             if (nfo == 0) {
(gdb)
704                             nx = 0;
(gdb)
706                             if (MB_CUR_MAX > 1)
(gdb)
710                                     i = getc(ifile);
(gdb)
711                             if (i == EOF)
(gdb) x/c &i
0x7fffffffd498: 52 '4'

NOTE: The third param '4' has been read

(gdb) n
713                             if (ip)
(gdb)
716                     if (i >= 040)                   /* zapped: && i < 0177

*/
(gdb)
717                             goto g4;
(gdb)
726             if (ismot(i))
(gdb)
728             if (copyf == 0 && sfbits(i) == 0)
(gdb)
730             if (cbits(i) == eschar && !raw)
(gdb)
732             return(i);
(gdb) s
733     }
(gdb)
getch () at n1.c:422
422             if (ismot(i))
(
(gdb) n
424             k = cbits(i);
(gdb)
425             if (k >= sizeof(gchtab)/sizeof(gchtab[0]) || gchtab[k] == 0)

/* nothing special */
(gdb) p k
$4 = 52
(gdb) n
426                     return(i);
(gdb) p i
$5 = 52

NOTE: Still got the '4'.

(gdb)
$6 = 52
(gdb) s
645     }
(gdb)
flushi () at n1.c:858
858             while (!nlflg) {
(gdb)
859                     if (donef && frame == stk)
(gdb)
861                     getch();
(gdb)
getch () at n1.c:411
411             if (ch) {
(gdb) n
419             if (nlflg)
(gdb)
421             i = getch0();
(gdb)
422             if (ismot(i))
(gdb)
424             k = cbits(i);
(gdb)
425             if (k >= sizeof(gchtab)/sizeof(gchtab[0]) || gchtab[k] == 0)

/* nothing special */
(gdb)
427             if (k != ESC) {
(gdb)
428                     if (k == '\n') {
(gdb)
429                             nlflg++;

NOTE: Now got the new line, nothing has been done with the '4' (discarded)

(gdb)
430                             if (ip == 0)
(gdb)
431                                     numtabp[CD].val++; /* line number */
(gdb)
432                             return(k);
(gdb)
645     }
(gdb)
flushi () at n1.c:858
858             while (!nlflg) {
(gdb)
863             copyf--;
(gdb)
864     }

NOTE: And 'flushi' returns having consumed up to the new line.

This shows that p9roff (this version at least) does not support conditional
.bd at all because it never switches to the S font, and ignores the 3rd
parameter.

If the test script is changed so that "\fS\(mu\fB" is used rather than just "\
(mu", the grout changes:-

[derij@pip Plan9_troff (master)]$ troff -d -t255 bdtest.ms
troff/nroff version March 11, 1994
invoke request ds
invoke request ds
invoke request bd
x T utf
x res 720 1 1
x init
V0
p1
x font 1 R
x font 2 I
x font 3 B
x font 4 BI
x font 5 CW
x font 6 H
x font 7 HI
x font 8 HB
x font 9 S1
x font 10 S
s10
f3
H720
V120
c8
f10
h50Cmu
h2Cmu
f3
558n120 0
x trailer
V7920
x stop

NOTE: 'mu' is bolded by 'h2' (one less than the 2nd param) so again this is
unconditional bolding, and the 3rd arg has been ignored.

What have I learned?

p9roff does not handle '.bd S 3 3' properly.

Because the only output device is 'utf' it never has to switch to a 'special'
font, so conditional bolding is obsolete.

This is probably not the Plan 9 roff before unicode was 'invented'.

Cheers

Deri



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