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diff --git a/info/digests/tex-implementors/message.44 b/info/digests/tex-implementors/message.44 new file mode 100644 index 0000000000..c2defa8449 --- /dev/null +++ b/info/digests/tex-implementors/message.44 @@ -0,0 +1,1290 @@ +TeX 3.14159 and other updates -- file 1 of 2 + +This and the following messages contain the details of bug reports +sent to Don Knuth, edited somewhat for brevity, and his responses. + +As already announced, the new release -- TeX 3.14159, MF 2.718 and +related TeX- and MFware -- is at labrea.stanford.edu in the file +~ftp/alpha/tex95.tar.gz . No arrangements have been made yet to +install the unpacked versions into the /tex area at labrea, from +which it can be mirrored to CTAN; I will try to do that as soon +as possible. + +This message begins with a complete contents list of the main topics +in this collection, to help you find items of interest quickly. I +have just sent out the reward checks with the annotated originals +of the reports as Don returned them to me. They should be arriving +at their destinations soon. + + +######################################################################## + +Contents: + >>> TeXbook / MFbook / documentation bugs + +++ glitch in errata.five at labrea + +++ MFbook, page 134 and others from Robert Hunt + +++ MFbook, page 143 + +++ MFbook, several from Denis Roegel + +++ Spurious TAB in errorlog.tex + >>> The TeX program + +++ trap_zero_glue bugette + +++ font_mem_max and other memory parameters + [ continued in file message.045 ] + >>> plain.tex + +++ \oalign and \d{} + +++ hyphenation inhibited by struts + +++ TeXbook, page 363, in \endinsert + >>> Metafont + +++ arithmetic overflow with z=whatever[z',z''] + +++ several reports from Bogus{\l}aw Jackowski + >>> CM fonts + +++ missing "cmchar"s in bigdel.mf + +++ shaved_stem vs. cap_stem in greeku.mf + +++ miscellanea from Robert Hunt, mostly in CM sources + +++ cap_ess in cmmi12 and larger + +++ possible glitch in cmbx5 and cmbx6 + +++ arithmetic overflow in CMinch + +++ sterling sign + >>> Fontware + +++ testfont.tex + +++ VPtoVF + +************************************************************************ +[ dek -- + Robert Hunt: C134 $2.56, C207 $2.56, C257 $2.56, A354 $2.56, + A359 $2.56, A360 $2.56, A361 $2.56, A362 $2.56, + A362 $2.56, E95(97) $2.56, E187 $2.56, E113 $2.56, + E233 $2.56, E438 $2.56, C129 $2.56, E491 $2.56 + Chris Thompson: C206 $2.56, TeX\S549 $327.68 + Michael Barr: A357 $2.56 + Peter Schmitt: C143 $.32 + Marek Ry\'cko: A31 $2.56 + Bogus\l{}aw Jackowski: MF\S815 $327.68, CSCSPU bugfix $2.56 + Denis B. Roegel: C94 $2.56, C107 $2.56, C355 $2.56 + Eberhard Mattes: TeX\S634 $2.56 + Jim Sterken: TeX\S625 $2.56 + Rainer Schoepf: B503 $2.56 + Bernd Raichle: A374 $.32 + Barbara Beeton: C354 $2.56 + Berthold Horn: TeX\S1323 $20.48 + Pierre MacKay: E291 $.32 + Walter Carlip: TeX\S717 $10.24 + Andrew K. Trevorrow: TeX\S549 $20.48 + Yannis Haralambous: E239 $2.56 + J"org Knappen: A356 $2.56 + Petr Sojka: A356 $2.56 + Ulrik Vieth: A363 $2.56 +] + +>>> TeXbook / MFbook / documentation bugs + + +++ glitch in errata.five at labrea + +in errata.five: + \bugonpage C282, the three lines following the chart (9/39/89) +should be ^ + \bugonpage C282, the three lines following the chart (9/30/89) +[ dek * ] + + ---------------------------------------------------------------------- + + +++ MFbook, page 134 and others from Robert Hunt + +Date: Thu, 16 Apr 92 15:57:44 BST +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Barbara Beeton <BNB@MATH.AMS.COM> +Cc: Robert Hunt <REH10@phx.cam.ac.uk> +Subject: MFbook p.134 bug from Robert Hunt + +Here is another one from Robert: + +> MFbook, page 134 (line 7933 of mfbook.tex) should read +> ...if $t\le 0$, precontrol~$t$ of~$p$ is~$z_0$. +> (rather than $z_n$). +[ dek -- $2.56 +] + +He's right. The z_n has somehow got duplicated from the previous +sentence. + +Chris Thompson +JANET: cet1@uk.ac.cam.phx +Internet: cet1@phx.cam.ac.uk +------- +Date: Thu, 07 May 92 22:37:53 BST +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Barbara Beeton <BNB@MATH.AMS.COM> +Cc: Robert Hunt <REH10@phx.cam.ac.uk> +Subject: Miscellany from Robert Hunt + +Barbara, + + Here are three things from Robert Hunt (his messages to me marked +with ">"): + +1. (7 May): +[ this has been resolved already ] + +2. (22 Apr, after I had been publicising the errata.* files locally): +> Is there any way of telling how far back it's necessary to go through +> the "Bugs in Computers and Typesetting" files in order to make sure +> that you have all the necessary changes? I very recently bought a copy +> of the softback version of the METAFONTbook, which says "6th printing, +> revised, February 1991" inside; but some of the changes listed in even +> only the third file (which covers the period up to June 1987) have not +> been made to it. As a typical example, the correction to page 14 (to +> mention Paul de Casteljau as the discoverer of the recursive midpoint +> rule) has not been made; but the correction to page 348, to include +> his name in the index, has! The same is true of the bugs listed in the +> fourth file and so on, which makes the book somewhat inconsistent in +> places. Is it possible that the printers have accidentally lost some +> of the updates, perhaps? +[ dek -- yes + AW totally screwed this up and i was bl**dy *ngry +] + +I must admit I didn't entirely believe this until Robert actually +turned up with his copy of the book today: the example he gives is +certainly correct. Very odd. Do you know whether anything more than +usually peculiar happened to the 6th softcover printing? (The current +mfbook.tex at labrea purports to represent the 7th softcover printing.) +If not, who could answer Robert's questions? + +3. (7 May): +> My candidate for the most trivial error in the METAFONTbook: on page +> 207, line 10, "-.00005" should read "-0.0005". + +Yes, that is an error, not yet fixed in mfbook.tex. But I'm sure we can +find one yet more trivial, can't we? ... + +Actually, I tried to reproduce the numbers on pages 206-207 by +[ dek -- $2.56 +] +compiling io.mf (from labrea) with mode=lowres;autorounding:={0 or 1}; +tracingspecs:=1 and I get numbers a teeny bit different from what is +in the text. For example, instead of "point (10.85146,-0.0005), where +there was a horizontal tangent, has been rounded to (10.85872,0)", I get +(10.85147,-0.00049) and (10.85873,0). Maybe the rounding details in MF +have changed since DEK did the run that produced these numbers. +[ dek -- $2.56 + Yes that was either bug #550 or 560. or both +] + +Chris Thompson +JANET: cet1@uk.ac.cam.phx +Internet: cet1@phx.cam.ac.uk +------- +Date: 19 May 1992 22:50:35 -0300 (BST) +From: Chris Thompson <CET1@phx.cam.ac.uk> +Subject: Yet another MFbook bug from Robert Hunt + +Barbara, + + The following from Robert Hunt (11 May; I was ill last week and +am only now getting round to clearing some of the backlog): +[ dek -- (and here i sit on a chilly day in California 26 Feb 199_5_, + coughing as I try to reduce the _secondary_ backlog.) + Hope you're feeling better by now, Chris! +] + +> On page 257 of the METAFONTbook, line 5 (the large centred display), +> the bracketed entries |numeric| |<| |numeric| (etc.) should read +> \<numeric> |<| \<numeric> instead. +[ dek -- $2.56 + (maybe should be $2.57 instead?) +] + +He's right: the two stacks (boolean, numeric, pair, string, transform) +should be <...> types, not boldface words, for consistency with the +rest of Appendix B. Not fixed in the latest mfbook.tex available to me. + +Chris Thompson +------- +[ dek -- However -- Why was I not told this in 1992 or 1993? + I could then have fixed the final printing of MFbook. + Changes since 93 affect the electronic copy _only_; + the hardcopy is frozen now for vols A, B, C, E. +] + + ---------------------------------------------------------------------- + + +++ MFbook, page 143 + +Date: Thu, 08 Jul 93 15:03:58 MEZ +From: Peter Schmitt <A8131DAL@AWIUNI11.EDVZ.UniVie.AC.AT> +To: INFO-TEX <@cunyvm.cuny.edu:INFO-TEX@SHSU.BITNET> +Subject: bugs in MFbook and TeXbook + +Since this topic is just discussed: + I recently noticed two `bugs' in the MFbook which + --- as far as I could see from the Errata --- have not + yet been corrected: + +%%%% +The METAFONTbook +Fourth printing, revised, September 1991 + +[ first one has been fixed ] + +page 143, line 2 : `giving the next exprs:' + should read `giving the next expressions:' +%%%% + +[...] + +Peter + +Peter Schmitt a8131dal@awiuni11.edvz.univie.ac.at + schmitt@awirap.bitnet +----------------------------------------------------------------------------- +Institute of Mathematics Strudlhofgasse 4 +[ dek -- great name ^^^^^^^^^^^^^^ +] +University of Vienna A-1090 Wien + Austria +------- +Date: 08 Jul 1993 15:37:56 -0300 (BST) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Peter Schmitt <A8131DAL@AWIUNI11.EDVZ.UNIVIE.AC.AT> +Subject: Re: [bugs in MFbook and TeXbook] + +Reply to Peter Schmitt, copied to Barbara Beeton. + +[...] + +> page 143, line 2 : `giving the next exprs:' +> should read `giving the next expressions:' +> %%%% + +This is unchanged in the most recent mfbook.tex available to me. +It does read rather oddly. I wonder whether the 'expr' was meant +to be in \tt? +[ dek -- 32\cents +] + +Chris Thompson +------- +[ dek -- Not an error -- when you input _expr.mf_ the computer types + _``Gimme an expr: ''_ and I was just appropriating that + neologism into English. Like `ftp' and `grep'. + However I do admint that a reasonable person might wonder at + my idiosyncratic style, so I'll change to \tt and pay the + normal reward of 32\cents for suggestions. +] + + ---------------------------------------------------------------------- + + +++ MFbook, several from Denis Roegel + +Date: 04 May 1994 16:58:42 +0200 +From: "Denis B. Roegel" <Denis.Roegel@loria.fr> +Cc: roegel@lorraine.loria.fr (Denis B. Roegel) +Subject: bugs in the METAFONTbook + +Mrs Beeton, + +I found two small bugs in my copy of the +METAFONTbook (hardcopy). I went through the last +erratas and found no mention of them. + +Here they are: + +1) page 94: last paragraph, 4th line: the word "are" + is duplicated. +[ dek -- $2.56 +] + +2) [resolved ] + +Thak you, + +Denis. (roegel@loria.fr) +------- +Date: 05 May 1994 17:14:40 +0200 (MET DST) +From: "Denis B. Roegel" <Denis.Roegel@loria.fr> +Subject: Re: bugs in the METAFONTbook + +[...] + +Maybe there is another bug in the MFbook: + +In the first paragraph of page 115, the instruction +"endchar" in the program at the end of chapter 12 +is mentionned. However, there is no "endchar" in +the program at the end of chapter 12. +[ dek -- $2.56 page 107 +] + +Denis. +------- +(reply, 05 May 1994) +thanks for your additional report. +the "dangerous bend" program in the file manfnt.mf is just a bit +different from what is in the mfbook, and does end with an +"endchar" -- preceded by another line not in the mfbook. for +some reason, this bug (i'm sure it is!) sounds familiar to me, +but i can't find a reference, and it's not corrected in any of +the errata files. +onto the dek list it goes ... +cheers. -- bb +------- + + ---------------------------------------------------------------------- + + +++ Spurious TAB in errorlog.tex + +[ from comp.text.tex, 21 Jan 95 ] +Date: 20 Jan 1995 12:38:36 GMT +From: schwab@issan.informatik.uni-dortmund.de (Andreas Schwab) +Subject: Spurious TAB in errorlog.tex + +There is a spurious TAB in the file systems/knuth/errata/errorlog.tex, +as found on the CTAN, in line 2867, containing the text "(Mattes and +Raichle). @1036". This TAB (after the word Mattes) causes a Greek Psi +[ dek * ] +to be typeset where a space should have been, looking a bit funny :-). + +-- +Andreas Schwab "And now for something +schwab@issan.informatik.uni-dortmund.de completely different" +=========================================================================== +[ dek -- _Thanks_ +] + +<<< end TeXbook / MFbook / documentation bugs + +************************************************************************ + +>>> The TeX program + + +++ trap_zero_glue bugette + +Date: 28 Oct 1993 16:26:02 +0000 (GMT) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Rainer Schoepf <Schoepf@sc.ZIB-Berlin.DE> +Subject: Re: [interesting effect in overfull box printout] + +Rainer, + +Yes, I think you have discovered a bugette. CC'ing this to Barbara. + +You write (omiting the history as to why you were changing latex.tex) +> +> Studying TeX the program I found what I think is an oversight: +> whenever a glue node is generated, either when scanning a glue +> specification in assignment, as well as in glue register arithmetic, +> the procedure trap_zero_glue is called to replace references to zero +> glue to a reference to the special object zero_glue. + +Actually, this is a bit too strong. |trap_zero_glue| is only called +when setting a `glue register or parameter', as the preamble to section +1229 says. For example, in + + \setbox0=\hbox{Foo\hskip 0pt plus 0pt minus 0pt Bar} + +the glue node doesn't point to |zero_glue|, but to a private |glue_spec| +with zero contents. + +> The only +> exception to this rule is scanning the glue specification after +> \tabskip in preparation of an alignment preamble. Therefore, +> +> \tabskip=\z@ +> +> generates a new glue node with zero fields, whereas +> +> \tabskip=\z@skip +> +> generates only a reference to zero_glue. + +I agree. This breaks the invariant promised in #1229. +[ dek -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +] + +> Now, since the overfull box +> printer checks only for equivalence with zero_glue, a blank is printed +> in the first case. + +[The code in |short_display| (section 175)] + +> The only other difference I could find is in TeX's +> processing of alignment entries: in a certain case the tabskip glue +> reference is replaced by zero_glue unless it is already zero_glue, +> i.e. this code is executed without it really being necessary. + +I can find no way other than |short_display| of making the difference +visible, which is why I call it a bugette rather than a bug. Some +glue parameters are tested for being zero by pointer comparison with +|zero_glue|, but \tabskip isn't one of them. + +> I cannot think of a reason why this behaviour should influence +> anything other than the overfull box printing, yet I think it should +[ dek -- also tracingparagraphs \S857 +] +> be changed in the next update to tex.web. It seems to me that a simple +> call to trap_zero_glue should suffice. + +Specifically, in |get_preamble_token|, section 782. There will need +to be a forward declaration of |trap_zero_glue| as well. +[ dek -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +] + +> What do you think? + +I think it should go on Barbara's list for Don. + +Chris Thompson +------- +Date: 28 Oct 1993 17:39:56 +0100 +From: schoepf@sc.ZIB-Berlin.DE (Rainer Schoepf) +To: Chris Thompson <CET1@phx.cam.ac.uk> +Cc: Barbara Beeton <BNB@MATH.AMS.ORG>, Rainer Schoepf <Schoepf@sc.ZIB-Berlin.DE> +Subject: Re: [interesting effect in overfull box printout] + +Chris, + +I wrote: + + > > The only other difference I could find is in TeX's + > > processing of alignment entries: in a certain case the tabskip glue + > > reference is replaced by zero_glue unless it is already zero_glue, + > > i.e. this code is executed without it really being necessary. + +to which you replied: + + > I can find no way other than |short_display| of making the difference + > visible, which is why I call it a bugette rather than a bug. + +I agree. + + > Some + > glue parameters are tested for being zero by pointer comparison with + > |zero_glue|, but \tabskip isn't one of them. + +But it is, in the piece of code labelled +[ dek -- ---? that's _not_ a pointer comparison to zero_glue +] + + <Nullify |width(q)| and the tabskip glue following this column@> + +If I understand this correctly, the local variable s points to a copy +of the tabskip glue of that point. But that doesn't influence the +outcome in any way. +------- +Date: 28 Oct 1993 18:06:22 +0000 (GMT) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Rainer Schoepf <Schoepf@sc.ZIB-Berlin.DE> +Subject: Re: [interesting effect in overfull box printout] + +Rainer, + +> > Some +> > glue parameters are tested for being zero by pointer comparison with +> > |zero_glue|, but \tabskip isn't one of them. +> +> But it is, in the piece of code labelled +> +> <Nullify |width(q)| and the tabskip glue following this column@> +> +> If I understand this correctly, the local variable s points to a copy +> of the tabskip glue of that point. But that doesn't influence the +> outcome in any way. + +Maybe I expressed that wrongly. I meant that there were no cases of +comparing \tabskip directly out of |equiv(glue_base+tab_skip_code)| +with |zero_glue|, in the way that there is for \spaceskip and +\xspaceskip in |main_control|, for example. The code in section 802 +that you mention is comparing glue copied from \tabskip (sharing its +|glue_spec|, admittedly) and as you say it doesn't effect the outcome, +as the test against the glue already being |zero_glue| is only an +optimization and could be omitted entirely. + +Chris Thompson +Internet: cet1@phx.cam.ac.uk +JANET: cet1@uk.ac.cam.phx +------- +[ dek -- I hesitate to change anything here, on the off chance that I did + have a reason for the ``redundant'' code in \S802 ... something + way back in my memory warns me to leave this alone. I will just + change the slightly-false comment in \S1229. + Of course I am 99.9999% certain that I could safely make the + change you suggest, but it is a big pain to handle the forward + referencing [I probably would put \S1229 into a section of its + own named Declare the procedure trap_zero_glue, and place that + in 782.] -- requires reprinting many pages of the book. Much + too much trouble for very little gain at this late late stage. +] + + ---------------------------------------------------------------------- + + +++ font_mem_max and other memory parameters + +Date: 17 Dec 1993 16:01:52 -0500 (EST) +From: Berthold Horn <71172.524@CompuServe.COM> +Subject: Re: where to send bug report + +Dear Barbara: + +[...] + +[ dek * ] +(1) OK, here it is. I don't know whether to call it a `real' bug since it +only comes up if one implements Knuth's scheme for growing +main memory in TeX (which is why TeX implementers haven't +run into it before --- except possibly Barry Smith? with Textures). +But then Knuth did describe how it is supposed to work... + +In 174 (page 71 of `TeX: the program') it should say: + + begin while p \ne null do +[ dek -- No this is not robust in the presence of clobbered lists -- You + are asking me to _undo_ one of the important corrections I made + years ago. +] + +instead of: + + begin while p > mem_min do + +On machines with fixed main memory (or in iniTeX), these happen to be +equivalent because` mem_min' is zero, just as `null' is zero. But when +[ dek -- ?? null is -30000 on my system at home, for instance. +] +memory grows downwards, then `mem_min' is negative, and one can get +caught in a delightful infinite loop while looking for the null at the end of +a list! The same problem occurs in 182 (page 74), Fortunately nowhere else. + +An alternate `fix' would be to redefine null to be the same as memmin, +but that would be a very poor solution since in dynamic allocation, +mem_min changes from time to time. + +(2) While I have your attention, I'd like to complain about a recent +implementaiton decision +that is a pain for dynamic memory allocation. For `bcharlabel' is used +`fontmemptr'. For a system with fixed allocations, this is a reasonable +[ dek - ^^^ size +] +way to say this doesn't point to any valid font, but its no good if font memory +can grow. I replaced this with `maxhalfword', which is fixed. Plus, when a +format file is read in, I try and figure out what value of fontmemptr was used +when it was dumped and replace that with `maxhalfword'. Its important for +a format file not too have too many frozen in dependencies on allocations. +One should be able to handle at least variations in size of main memory, +string pool size, font memory size, hyphenation table size etc. + +(3) By the way, I am wondering why we still seem to be using maxhalfword = +262144 +when there aren't really any 36 bit machines left (been I while since I hacked + on a PDP6 or PDP10 :=), and everyone is using +[ dek -- ^^^^^^^^ in fantasy land +] +64 bit words. Doesn't make sense in a 32 bit address space world... + +(4) Finally, I'd like to recommend that --- given that we are using 64 bit +words --- +the TeX 82 limitation in fontmax == 256 be lifted. We did this in Y&YTeX on +[ dek -- ^^^^^^^^^ + This would break the _Pascal_ implementation that still exists, + I think? +] +an experimental basis and it involves only a tiny change where font definitions +are written to the DVI file, and a tiny change where font changes are written +to the DVI file. DVI processors are already supposed to be able to +understand the multi-byte font commands (despite the fact that TeX 82 +never generates them) - although, the `level 0' standard does allow them +to support only 256 internal font numbers (a weird and wonderful contraction +if you ask me). + +[...] +[ dek -- These things are up to implementors' discretion. + Something in the back of my mind triggers a caution flag -- + not only in the memory for hyphenation but also in the \span + feature of alignments, I fear (?) Good luck. +] + +Berthold & Blenda. +------- +Date: 09 Mar 1994 16:59:50 -0500 (EST) +From: andrew.trevorrow@anu.edu.au (Andrew K Trevorrow) +Subject: new TeX bug + +Hi Barbara, + +I think I've found a bug in TeX. Please pass on the following note to the +TeX implementors to verify my analysis. + + ---------------- + +Over the last couple of years a few OzTeX users have reported a strange bug +in which a character at the start of a word changes for no obvious reason. +I was never able to reproduce the problem until the other day when +Ole Michael Selberg sent me the vital clue: the problem only happens if +font_mem_size is increased and the format file is NOT rebuilt. +(OzTeX users don't have to recompile TeX to change font_mem_size; +they simply edit a number in a configuration file.) + +Now font_mem_size is supposed to be one of the parameters that can differ +in INITEX and VIRTEX. The problem is that non_address is set to font_mem_size, +so when bchar_label[f] values are set to non_address and stored in a format +file by INITEX they will not be recognized as non-address values by a VIRTEX +that uses a different font_mem_size! + +Note that if font_mem_size in VIRTEX is smaller than the INITEX value +then a fatal format error will occur when loading bchar_label[nullfont] +(which was set to non_address by INITEX). If font_mem_size in VIRTEX is +larger than the INITEX value then far nastier problems can occur, such as +a character at the start of a word changing. + +One solution would be to treat font_mem_size like hash_size and the other +parameters that require format files to be rebuilt if their values change. +A better solution is to set non_address to -1; this allows font_mem_size to +be different in INITEX and VIRTEX. Here are the changes needed to tex.web: + +@x +@!font_index=0..font_mem_size; {index into |font_info|} +@y +@!font_index=-1..font_mem_size; {index into |font_info|} +@z +[ dek -- Now many compilers will refuse to pack properly +] + +@x +@d non_address==font_mem_size {a spurious |font_index|} +@y +@d non_address==-1 {a spurious |font_index|} +@z + +@x +if bchar_label[hf]<non_address then {put left boundary at beginning of new line} +@y +if bchar_label[hf]<>non_address then {put left boundary at beginning of new line} +@z + +@x +undump(0)(font_mem_size)(bchar_label[k]); +@y +undump(non_address)(font_mem_size-1)(bchar_label[k]); +@z + +I've included these changes in a new version of OzTeX and they fix the bug. + +Andrew Trevorrow +akt150@huxley.anu.edu.au +------- +Date: 09 Mar 1994 11:08:17 -0500 (EST) +From: Louis Vosloo <71172.524@CompuServe.COM> +Subject: [andrew.trevorrow@anu.edu.au (Andrew K Trevorrow): new TeX bug] + +Dear Barbara: + +I believe I already reported on this problem. font_mem_max is used +[ dek -- ^^^ size +] +as a special value for bchar etc. Which is fine if font_mem_max never +changes, but for a `dynamic' TeX (like Y&YTeX) this doesn't work. + +My solution was to change this to max_half_word. + +In addition, my format undumping code tries to figure out +what value was used in the dumped format and then replaces that +systematically with max_half_word. +That way it can handle `old' format files made before the fix as well. + +Berthold K.P. Horn +71172.524@compuserve.com +------- +Date: 09 Mar 1994 11:25:40 -0500 (EST) +From: Berthold Horn <71172.524@CompuServe.COM> +Subject: [andrew.trevorrow@anu.edu.au (Andrew K Trevorrow): new TeX bug] + +Dear Barbara: + +The following is extracted from email I sent to you on 93/Dec/17. +The bug reported by Trevor is mentioned below in item (2) + +Regards, Berthold. + +... + +(1) OK, here it is. I don't know whether to call it a `real' bug since it +only comes up if one implements Knuth's scheme [...] + + [ remainder of message as above ] +------- +Date: 09 Mar 1994 17:02:14 +0000 (GMT) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Barbara Beeton <BNB@MATH.AMS.ORG> +Cc: Andrew Trevorrow <andrew.trevorrow@anu.edu.au> +Subject: Andrew Trevorrow's new TeX bug + +Barbara, + + I am replying directly to you rather than to the tex-implementors list, +with a copy to Andrew. + +> ... as soon as the problem has +> been verified, i'll forward it to knuth. (it's getting to be +> time for his annual tex-inspection tour.) +[ dek -- ^^^^^^ + exponentially decreasing, actually, although I am one year + behind plan (not two) +] + +About time :-) It gets later every year... +[ dek -- \check +] + +> Now font_mem_size is supposed to be one of the parameters that can differ in +> INITEX and VIRTEX. The problem is that non_address is set to font_mem_size, +> so when bchar_label[f] values are set to non_address and stored in a format +> file by INITEX they will not be recognized as non-address values by a VIRTEX +> that uses a different font_mem_size! +> +> Note that if font_mem_size in VIRTEX is smaller than the INITEX value +> then a fatal format error will occur when loading bchar_label[nullfont] +> (which was set to non_address by INITEX). If font_mem_size in VIRTEX is +> larger than the INITEX value then far nastier problems can occur, such as +> a character at the start of a word changing. + +Yes, this is a bug, and a quite nasty one too. Introduced by the changes +in TeX version 3, so presumably Andrew only gets the smaller reward. +[ dek -- (Berthold) +] + +> One solution would be to treat font_mem_size like hash_size and the other +> parameters that require format files to be rebuilt if their values change. +> A better solution is to set non_address to -1; this allows font_mem_size to +> be different in INITEX and VIRTEX. + +Putting |non_address| at the other end of the range seems to be the +right solution. I think it could equally well be set to 0 as to -1. +[ dek -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +] +The values in the |bchar_label| array can never be this small naturally: +they are true indices into |font_info| rather than offset ones. + +There is a technical problem about making this change to TeX. One needs +[ dek -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +] +to force old format files to be invalid, because the |non_address| +values in them would be wrongly interpreted (even more so than at +present, that is!). This wouldn't happen "naturally". + +My MVS version of TeX has hacks to make |font_index| a signed 16-bit +value, starting at |font_mem_base| (currently dumped in the format file) +rather than zero. I can foresee myself having to rework this... + +Chris Thompson +Cambridge University Computing Service +------- +Date: 09 Mar 1994 13:04:02 -0500 (EST) +From: bbeeton <BNB@MATH.AMS.ORG> +To: CET1@phx.cam.ac.uk +Cc: BNB@MATH.AMS.ORG, andrew.trevorrow@anu.edu.au +Subject: Re: Andrew Trevorrow's new TeX bug + +chris and andrew, +berthold horn has reminded me that he reported this bug in december; +i did forward his message to you then, chris, but it seems to have +got lost. attached is the forwarded message, along with some of +today's commentary from berthold. he avers that setting non_address +to -1 won't work under certain circumstances, and proposes another +solution that does work for him. + +this seems to be more contentious than i expected. perhaps a wider +discussion is warranted -- i've already received (but not read) +a few other messages on the subject, including one from peter +breitenlohner. +cheers. -- bb + -------------------- + +Date: 17 Dec 1993 16:27:33 -0500 (EST) +From: bbeeton <BNB@MATH.AMS.ORG> +To: cet1@cus.cam.ac.uk +Subject: [Berthold Horn <71172.524@CompuServe.COM>: Re: where to send bug + report] + +chris, +would appreciate it if you could verify this bug report, and +perhaps comment on the other points made in the message. + +best wishes for the holidays. + -- bb + --------------- + +Date: 17 Dec 1993 16:01:52 -0500 (EST) +From: Berthold Horn <71172.524@CompuServe.COM> +To: bbeeton <BNB@MATH.AMS.ORG> +Subject: Re: where to send bug report + +Dear Barbara: + +[...] + +(1) OK, here it is. I don't know whether to call it a `real' bug since it +only comes up if one implements Knuth's scheme [...] + + [ remainder of message as above ] + + -------------------- + +Date: 09 Mar 1994 11:08:17 -0500 (EST) +From: Berthold Horn <71172.524@CompuServe.COM> +To: bbeeton <BNB@MATH.AMS.ORG> +Subject: [andrew.trevorrow@anu.edu.au (Andrew K Trevorrow): new TeX bug] + +Dear Barbara: + +I believe I already reported on this problem. font_mem_max is used +as a special value for bchar etc. Which is fine if font_mem_max never +changes, but for a `dynamic' TeX (like Y&YTeX) this doesn't work. + +My solution was to change this to max_half_word. + +In addition, my format undumping code tries to figure out +what value was used in the dumped format and then replaces that +systematically with max_half_word. +That way it can handle `old' format files made before the fix as well. + +Berthold K.P. Horn +71172.524@compuserve.com +------- +Date: 09 Mar 1994 18:39:51 +0000 (GMT) +From: Peter Breitenlohner <PEB%DMUMPIWH.BITNET@vm.gmd.de> +To: bbeeton <BNB@MATH.AMS.ORG> +Subject: Re: [andrew.trevorrow@anu.edu.au (Andrew K Trevorrow): new TeX bug] + +Barbara, +1. this is definitely a bug +2. The fix is no good (incomplete). There is at least one place in + tex.web which now says + if bchar_label[hf]<non_address + and changing non_address from very large too very small requires a change + here too (I'll check if there are more places) +3. I dislike the change of font_index=0..font_mem_size into + font_index=-1..font_mem_size because on some systems that may have + the effect that 4 bytes instead 2 bytes are required for a font_index +4. I think one can safely set non_address=0 but I have to check that + and will send you a complete fix tomorrow. +5. I will also reformulate my "bug or design feature" msg from some + time ago and would like to ask you to forward it to don. +regards Peter +------- +(reply, 09 Mar 1994) +thanks much, peter. +[ forwarded all previous mail to peter ] +------- +Date: 09 Mar 1994 11:51:32 -0800 (PST) +From: drf@frame.com (David Fuchs) +Subject: Re: [andrew.trevorrow@anu.edu.au (Andrew K Trevorrow): new TeX bug] + +I'd forward it along to dek; [...] + + -drf +------- +(reply, 09 Mar 1994) +what's becoming clear about this particular bug is that it impinges +on some of the system-dependent areas, in particular, how various +implementors choose to implement the ability to change the size of +various memory blocks at run time. since more implementations do +have that ability now than formerly, and they all seem to be +implemented differently (though not all techniques are public), +this is potentially a rats nest. so information is important not +only on what the bug is and how you can make it happen, but what +else is related and where it might go wrong if fix x is adopted. +i think the present participants are capable of doing a pretty +thorough job. +------- +Date: 10 Mar 1994 11:27:26 +0000 (GMT) +From: Peter Breitenlohner <PEB%DMUMPIWH.BITNET@vm.gmd.de> +To: Barbara Beeton <bnb@MATH.AMS.ORG>, + Chris Thompson <cet1@phoenix.cambridge.ac.uk>, + Andrew Trevorrow <andrew.trevorrow@anu.edu.au>, + Berthold Horn <71172.524@compuserve.com> +Subject: andrews bug et alia + +hi barbara (and chris, andrew, berthold), +thanks for sending the various remarks, here my comments. + +1. andrews bug +yes, this definitely is a bug [...] since font_mem_size +is among those parameters that are explicitely allowed to differ between +VIRTEX and INITEX. + +andrews fix is bad for two reasons + a) the test ...<non_addres must be changed into ...>non_address + b) a bchar_label=-1 fails in undump where the value is tested to be + in the range 0..font_mem_size. +I did not think about Chris's point (invalidating old format files) but +had changed the test in undump anyway (general neatness) and this pays +[ dek - ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +] +nicely since it does catch the old formats that must be rebuilt when +non_address is changed from font_mem_size to 0 (not -1) as I would +recommend. + +I fully agree with Chris that non_address=0 is OK, and I strongly dislike +the -1 for various reasons (among others it unnecessarily forces font_index +to be signed instead of unsigned). + +I have looked into tex.web and am fully convinced that one can +safely set non_address=0 since font_info[0] is occupied +by the first of \nullfont's parameters. + +Here my proposed change: + +@x [30] m.549 l.10678 - bug fix +@d non_address==font_mem_size {a spurious |font_index|} +@y +@d non_address==0 {a spurious left boundary char label} +@z +%--------------------------------------- +@x [41] m.916 l.17965 - bug fix +if bchar_label[hf]<non_address then {put left boundary at beginning of new line} +@y +if bchar_label[hf]>non_address then {put left boundary at beginning of new line} +@z +%--------------------------------------- +@x [50] m.1323 l.24036 - bug fix +undump(0)(font_mem_size)(bchar_label[k]); +@y +undump(0)(fmem_ptr)(bchar_label[k]); +[ dek -- ^^ -1 +] +@z +%--------------------------------------- + +2. berthold horns msg from Dec 17 +ad 2: non_address=max_halfword is probably OK as well, I have not checked +all implications. I prefer =0 and this has the definite advantage that it +does catch old formats that need to be rebuilt. (Having to rebuild formats +when the program changes - even if the pool checksum doesn't change - +is certainly ok.) + +ad 3: that is entirely up to implementors, the 262144 never shows up in +tex.web. But bigTeX has to set some reasonable limit on the size of +the mem array otherwise a stupid paging system uses up enormous amounts of +paging space and non-paging systems are completely sunk. +Cetainly 256K is as good as any other number of the right size. + +ad 4: It would be tempting to increase font_max once max_halfword and +max_quarterword have been increased. TeX uses at present only one-byte +font numbers in the DVI file, i.e., range 0..255. Clearly TeX's dvi writing +routines could certainly be adapted to a larger range, no problem here. +But: Extending this range may have implications on existing DVI software. +Some DVI drivers may rely on one-byte font numbers (re: driver standard?). +Therefore I would be very careful at this point!! + +ad 1: I can't understand this problem. In VIRTEX mem_min must be <=mem_bot, +[ dek -- Might have lots of stuff between mem_bot and mem_min, with a + special allocation scheme +] +and mem_min>=min_halfword=null. Now mem_bot is a glue spec, hence can never +occur when traversing a list. If mem_min is mem_bot-1 or mem_bot-2 the one +or two extra words are never used and if mem_min<mem_bot-2 then mem[mem_min] +is also never used (done in undump memory). Hence the word mem[mem_min] +is either a glue spec or unused. This can never give a problem +with tests such as p>mem_min when traversing lists. +It might be nicer to test for p<>null but I think this is no bug. +Maybe only don knows why he has formulated this one test in a different way, +but probably he forgotten the reasoning behind that. + +A bug might creep in +if someone is dynamically extending the mem array during the run of +VIRTEX and is not doing it properly (mimicking the behaviour of undump). +I would say any problems introduced here are due to improper sys-dep +modifications. +[ dek -- \check +] + +regards peter +------- +Date: 10 Mar 1994 12:57:35 +0000 (GMT) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Barbara Beeton <BNB@MATH.AMS.ORG> +Cc: Andrew Trevorrow <andrew.trevorrow@anu.edu.au>, + Peter Breitenlohner <PEB@DMUMPIWH.EARN>, + Berthold Horn <71172.524@CompuServe.COM> +Subject: Re: Andrew Trevorrow's new TeX bug + +Barbara, + +> berthold horn has reminded me that he reported this bug in december; +> i did forward his message to you then, chris, but it seems to have +> got lost. + +I found this message in an archive. Apologies: it arrived too late +to be dealt with before Christmas, and got completely forgotten +afterwards. If you have anything else outstanding on the potential +bug list that I haven't replied to you about, please remind me a.s.a.p. + +> this seems to be more contentious than i expected. perhaps a wider +> discussion is warranted -- i've already received (but not read) +> a few other messages on the subject, including one from peter +> breitenlohner. + +I agree with Peter Breitenlohner (personal communication) and with +Bernd Raichle (in tex-implementors): there is absolutely no doubt +that this is a bug. I don't think Wayne's position is defensible: +I will post something to tex-implementors saying so. + +The main thing is to make sure the bug report is on the list for +Don. We could argue about the merits of particular ways of fixing +it until the cows come home, but it is Don who will actually make +that decision. + +Peter, Andrew and I all seem happy with |non_address| = 0. Peter +writes + +> ... I strongly dislike the -1 for various reasons (among others it +> unnecessarily forces font_index to be signed instead of unsigned). + +(Although an alternative would be to make |bchar_label| an |integer| +array rather than a |font_index| one.) + +Berthold suggests |non_address| = |max_halfword|, but I think this is +not portable. While many implementations may squeeze |font_index| +values into halfwords (indeed, I do myself) there is nothing in tex.web +to prevent |font_mem_size| from being larger than |max_halford|. +[ dek -- ^^ w +] +(There is curiosity, though: |font_params| is an array of |halfword|s. +Can one break TeX by setting \fontdimen<amazingly large number>? I will +have to think about that one.) +[ dek * ] + +I didn't intend my point about forcing the invalidation of old format +files to be a big issue (there are many ways to achieve the desired +effect): just something not to be forgotten. Andrew writes: + +> Maybe it would be a good idea to put some sort of version number (the +> current TeX version?) in format files. I wonder if there is a spot +> that would be guaranteed to catch all old formats? A suitable error +> message would be "This is an old format file; use INITEX to rebuild +> it.". + +It shouldn't be the TeX version number, because sometimes a version +change does not require new format files, which is convenient when +it happens. I have in the past fiddled with the 69069 at the end of the +file to achieve deliberate invalidation in local implementations, but +to get something like Andrew's message consistently one would want +something right at the beginning. + +To take Berthold's 4 sections in order: + +1. The |null| test. (I suspect that this is the only part of the message + I even glanced at in December.) My first inclination is to agree with + Peter's analysis, but I need to go through this in detail again. I + will let you know. + +2. = Andrew's bug, discussed above. + +3. Why not |max_halfword| > 262144 ? This is a question relating to + a particular implementation. + +4. Why not |font_max| > |font_base| + 256 ? I have wondered about that + myself. I don't think I can improve on Peter's analysis: + +> It would be tempting to increase font_max once max_halfword and +> max_quarterword have been increased. TeX uses at present only +> one-byte font numbers in the DVI file, i.e., range 0..255. Clearly +> TeX's dvi writing routines could certainly be adapted to a larger +> range, no problem here. +> But: Extending this range may have implications on existing DVI +> software. Some DVI drivers may rely on one-byte font numbers (re: +> driver standard?). Therefore I would be very careful at this point!! + +No harm in suggesting it to Don, I suppose. If he doesn't like it, +it is always open to an implementor to provide this extension via +the change file. +[ dek -- right ... see also \span (?) +] + +Chris Thompson +Cambridge University Computing Service +------- +Date: 10 Mar 1994 14:09:12 +0000 (GMT) +From: Peter Breitenlohner <PEB%DMUMPIWH.BITNET@vm.gmd.de> +To: Berthold Horn <71172.524@CompuServe.COM> +Cc: Barbara Beeton <bnb@MATH.AMS.ORG>, + Chris Thompson <cet1@phoenix.cambridge.ac.uk> +Subject: Re: andrews bug et alia + +On 10 Mar 94 08:03:11 EST you said: +> +>Believe me, this very definitely *is* a bug! Think about what happens when +>you extend the variable length node list downward. You can't very well then +>go back over all list structures and change `null' to the new `mem_min'! +> +>> A bug might creep in if someone is dynamically extending the mem array +>> during the run of VIRTEX and is not doing it properly (mimicking the +>> behaviour of undump). I would say any problems introduced here are due to +>> improper sys-dep modifications. +> +I think whenever you are dynamically allocating more mem-memory you should +1. never have mem_min<min_halfword=null and +[ dek - ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + Absolutely true (see \S116) +] +2. should never use mem[mem_min] (whatever the present mem_min value) unless + your proposed code change is made +3. never ever use mem[min_halfword]. +I agree a change in mod 174 ( p>mem_min => p<>null ) would be desirable +[ dek -- no, it could cause p to go outside the array bounds. +] +and would make life a little easier for those who want/have to dynamically +enlage mem at the low end. I only disagree that this can be called a bug. +The only point where standard TeX enlarges the low end of mem is when +a format is read and VIRTEX's mem_min is below INITEX's mem_bot. +And for this case Knuth's coding works fine, hence no bug +[ dek -- _NB_: show_mode_list, short_display are designed to avoid + crashing the system when TeX is buggy. See comment in \S182 +] + +regards peter +------- +Date: 12 Mar 1994 12:30:55 +0000 (GMT) +From: Peter Breitenlohner <PEB%DMUMPIWH.BITNET@vm.gmd.de> +To: Andrew K Trevorrow <andrew.trevorrow@anu.edu.au>, + Barbara Beeton <bnb@MATH.AMS.ORG> +Subject: Re: andrews bug et alia + +Hi Andrew, Barbara +On Sat, 12 Mar 94 14:14:40 EST you (andrew) said: +> +>By the way, I think that in your change to undump you should use +>fmem_ptr-1 rather than just fmem_ptr (which is the first UNUSED index +>in the font_info array). +> +To Andrew: That is indeed a good idea since it would catch old formats even +in the rare event that fmem_ptr=font_mem_size! +[ dek -- Actually I once noticed that "Web2C" omits the checking ... + We must make sure this test is _not_ skipped. +] +> +To Barbara: can you please append the above to my messsage with the proposed +fix. +> +regards peter +------- +Date: 10 Mar 1994 17:03:39 +0000 (GMT) +From: Chris Thompson <CET1@phx.cam.ac.uk> +To: Barbara Beeton <BNB@MATH.AMS.ORG> +Cc: Andrew Trevorrow <andrew.trevorrow@anu.edu.au>, + Peter Breitenlohner <PEB@DMUMPIWH.EARN>, + Berthold Horn <71172.524@CompuServe.COM> +Subject: Small TeX bug - \fontdimen <large-number> + +Barbara, + +I wrote: +> (There is curiosity, though: |font_params| is an array of |halfword|s. +> Can one break TeX by setting \fontdimen<amazingly large number>? I will +> have to think about that one.) + +There is, in fact, a bug here. The following code in TeX section 580, +part of |find_font_dimen|, + + begin repeat if fmem_ptr=font_mem_size then + overflow("font memory",font_mem_size); + font_info[fmem_ptr].sc:=0; incr(fmem_ptr); incr(font_params[f]); + until n=font_params[f]; + +contains no precautions to prevent |font_params[f]| from being +incremented from |max_halfword|, its largest legal value. What +happens next is implementation-dependant. In the case of the one +I was experimenting with, |halfword| values wrap quietly from +|max_halfword| to |min_halfword|, and so (for large enough |n|) +the loop test is never satisfied, and one gets a font memory +overflow condition (which is only mildly spurious). + +Possible fixes: make |font_params| an array of |integer|, or +|font_index| (maybe: not sure about this), instead of |halfword|. +Alternatively, in section 578 replace + + if n<=0 then cur_val:=fmem_ptr + +by + + if (n<=0) or (n>max_halfword) then cur_val:=fmem_ptr + +Chris Thompson +Cambridge University Computing Service +------- +Date: 12 Mar 1994 12:47:28 +0000 (GMT) +From: Peter Breitenlohner <PEB%DMUMPIWH.BITNET@vm.gmd.de> +To: Chris Thompson <CET1@PHOENIX.CAMBRIDGE.AC.UK> +Subject: Re: Small TeX bug - \fontdimen <large-number> + +On Thu, 10 Mar 94 17:03:39 GMT you said: +>Barbara, +> +>I wrote: +>> (There is curiosity, though: |font_params| is an array of |halfword|s. +>> Can one break TeX by setting \fontdimen<amazingly large number>? I will +>> have to think about that one.) +> +>There is, in fact, a bug here. The following code in TeX section 580, +>part of |find_font_dimen|, +> +> begin repeat if fmem_ptr=font_mem_size then +> overflow("font memory",font_mem_size); +> font_info[fmem_ptr].sc:=0; incr(fmem_ptr); incr(font_params[f]); +> until n=font_params[f]; +> +>contains no precautions to prevent |font_params[f]| from being +>incremented from |max_halfword|, its largest legal value. What +>happens next is implementation-dependant. In the case of the one +>I was experimenting with, |halfword| values wrap quietly from +>|max_halfword| to |min_halfword|, and so (for large enough |n|) +>the loop test is never satisfied, and one gets a font memory +>overflow condition (which is only mildly spurious). +> +>Possible fixes: make |font_params| an array of |integer|, or +>|font_index| (maybe: not sure about this), instead of |halfword|. +>Alternatively, in section 578 replace +> +> if n<=0 then cur_val:=fmem_ptr +> +>by +> +> if (n<=0) or (n>max_halfword) then cur_val:=fmem_ptr +> +Hi Chris, +1. I agree this is a bug and (from past experience) I would say you are due +for a cheque (a big one). Assuming font_mem_size>max_halfword the program may +[ dek -- $327.68 +] +attempt to assign a value >max_halfword to font_params[f]. If range checking +were on (who is nowadays running TeX with range checking on?) this would give a +"high bound violation" or however this is called in a particular systems. +Knuth has always classified such as bugs. (I once got a cheque for an even +more obscure range checking error.) + +As to a fix I have convinced myself that defining + @!font_params:array[internal_font_number] of font_index; {how many font +solves all problems and introduces no new ones. +In particular I have verified with a `virgin INITEX' with font_mem_size=32767 +that one can say "\fontdimen 32767 \nullfont" with no problems whereas + "\fontdimem 32768 \nullfont" leads to an overflow [font_mem... . +Hence TeX makes sure that font_params[f] is allways in the range +7..font_mem_size, i.e., a subset of font_index. + +As to the other possibilities: your alternative +> if (n<=0) or (n>max_halfword) then cur_val:=fmem_ptr +is not so good since the result is implementation dependent, on some +systems you can use \fontdimen n f with some very large n and on other +systems (or the same system with different switches) you can't. +I think Knuth's policy for such was that an error is not sufficient, +only a fatal error is good enough indication. +And whoever wants to set \fondimen 32000 f is probably out of his mind +anyway. + +2. Did you already have a chance to look at the e-TeX files ? + +regards peter +------- + +<<< end The TeX program + +************************************************************************ |