Date: Fri, 10 Jul 2020 16:44:00 -0700 From: Mark Millard <marklmi@yahoo.com> To: Yuri Pankov <yuripv@yuripv.dev> Cc: Steve Wills <swills@FreeBSD.org>, "daichi@freebsd.org" <daichi@FreeBSD.org>, FreeBSD Current <freebsd-current@freebsd.org>, Hiroki Sato <hrs@FreeBSD.org> Subject: Re: svn commit: r352558 - head/usr.bin/top Message-ID: <A6DA92D1-C98B-416F-B1FA-315AF943426D@yahoo.com> In-Reply-To: <BE3A2B48-D593-4733-8EAC-4C70F3F0B9B4@yahoo.com> References: <1BDFB387-930D-4F4D-8729-A5850F1C15B9.ref@yahoo.com> <1BDFB387-930D-4F4D-8729-A5850F1C15B9@yahoo.com> <61107ecc-6f9b-a4db-7b1e-ec75f73939ee@FreeBSD.org> <f8c8e434-39d7-4c7b-d33d-ef8a6b196eb9@yuripv.dev> <BE3A2B48-D593-4733-8EAC-4C70F3F0B9B4@yahoo.com>
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On 2020-Jul-10, at 15:25, Mark Millard <marklmi at yahoo.com> wrote: > On 2020-Jul-10, at 11:05, Yuri Pankov <yuripv at yuripv.dev> wrote: >=20 >> Steve Wills wrote: >>> On 11/28/19 4:08 PM, Mark Millard via svn-src-head wrote: >>>>> Author: daichi >>>>> Date: Fri Sep 20 17:37:23 2019 >>>>> New Revision: 352558 >>>>> URL: >>>>> https://svnweb.freebsd.org/changeset/base/352558 >>>>>=20 >>>>>=20 >>>>> Log: >>>>> top(1): support multibyte characters in command names (ARGV = array) >>>>> depending on locale. >>>>> - add setlocale() >>>>> - remove printable() function >>>>> - add VIS_OCTAL and VIS_SAFE to the flag of strvisx() to = display >>>>> non-printable characters that do not use C-style backslash = sequences >>>>> in three digit octal sequence, or remove it >>>>> This change allows multibyte characters to be displayed = according to >>>>> locale. If it is recognized as a non-display character according = to the >>>>> locale, it is displayed in three digit octal sequence. >>>>>=20 >>>>=20 >>>> Initially picking on tab characters as an example of what is >>>> probably a somewhat broader issue . . . >>>>=20 >>>> Ever since this change, characters like tabs that do not fit >>>> in the next character cell when output, but for which they >>>> are !isprintable(...), now mess up the top display. Again >>>> using tab as an example: line wrapping from the text having >>>> been shifted over by more than one character cell. top does >>>> not track the line wrapping result in how it decides what >>>> to output for the following display updates. >>>>=20 >>> Apologies for the way late reply here, but I just now bothered = tracking this down. This commit seems to be the cause of some corruption = I'm seeing in long running top(1) as well. As Mark mentions, if I use = "hh" it clears up. Should I open a bugzilla bug? I can share screenshots = of the corruption, such as: >>> https://i.imgur.com/Xqlwf9h.png >>> https://i.imgur.com/Jv0d5NU.png >>=20 >> Does removing VIS_SAFE fixes the issue for you? >>=20 >> As for original Mark's report (which I missed), removing = isprintable() doesn't look wrong as vis(3) should take of its = functionality (and in multibyte-aware way). >=20 > vis (as used) and the old isprintable logic are not > equivalent when multi-byte is not needed/involved. > Otherwise I'd not have had anything to ever report. > If vis can do what is needed, more work needed to > be done when the change was made in order to avoid > msesed up displays in single-byte contexts. >=20 >> Also, is there an easy way to reproduce this? >=20 > The following sort of command (the empty space inside quoted > text are tab characters): >=20 > # tr '0\n 1\n 2\n 3\n 4\n 5\n 6\n 7\n = 8\n' '\t0 \t1 \t2 \t3 \t4 \t5 \t6 \t7 = \t8' < /dev/zero > /dev/null >=20 > causes my 200 character wide window running top to show: >=20 > 32920 root 100 0 12764Ki 2420Ki CPU3 3 2:22 = 99.87% tr 0\\n 1\\n 2\\n 3\\n 4\\n 5\\n 6\\n 7\\n = 8\\n \\t0 \\t1 \\t2 \\t3 \\t4 \\t5 \\t6 \\t733 = \\t8 20 7172 5448Ki CPU23 23 0:00 0.04% top = -HiSCazopid >=20 > But that does not show where the lines wrap at the edges of the = window, > so breaking it up explicitly after the first "\" in \\7: >=20 > 32920 root 100 0 12764Ki 2420Ki CPU3 3 2:22 = 99.87% tr 0\\n 1\\n 2\\n 3\\n 4\\n 5\\n 6\\n 7\\n = 8\\n \\t0 \\t1 \\t2 \\t3 \\t4 \\t5 \\t6 \ > \t733 \\t8 20 7172 5448Ki CPU23 23 0:00 = 0.04% top -HiSCazopid >=20 > Note how \n turned into \\n , taking an extra character for > each \n . Similarly for \t vs. \\t . (Other examples do > similarly.) >=20 > The tab characters really do use more than one character cell > on the display (sometimes). >=20 > The text from the tr command ends up spread across 2 lines > as things look like in the window where top is running. >=20 > I ran top in another ssh session first and then the tr command. > Before running the tr command, top showed as: >=20 > 33019 root 20 0 17172Ki 5448Ki CPU24 24 0:00 = 0.05% top -HiSCazopid >=20 > If you do not end up with top listed just after tr in top's output, > then it will not be top's line that ends up partially overwritten. >=20 > If you have wider windows, you may need more text in the tr quoted > strings. >=20 > In another experiment I inserted a large number of backspace = characters > (control-H's) at the front of the first quoted string in the tr = command. > The top output displayed: >=20 > 0\\n5 ro1\\n 2\\93 3\\n12764\\n 25\\ni CP6\\n 97\\n:12 = 100.00\t0r \nHiS\\t1pid \\t2 \\t3 \\t4 \\t5 \\t6 \\t > 33094 root 20 0 17172Ki 5488Ki CPU21 21 0:00 = 0.06% top -HiSCazopid >=20 > In other words, backspace moved the cursor position back over prior > fields on the line and then the later line content overwrote those > fields instead of being after "tr" someplace (or truncated off). >=20 > Note that part of "-HiSCazopid" shows up on both lines. The extra > is from when top was running but tr had not started yet. top is > not managing text replacement correctly for output characters that > end up not being just "in" the next character-cell on the terminal. >=20 > The same sort of result happens when instead adding just one > carriage return (control-M) in front of that first quuoted > string instead: >=20 > 0\\n8 ro1\\n 2\\92 3\\n12764\\n 25\\ni CP6\\n 117\\n:11 = 100.00\t0r \nHiS\\t1pid \\t2 \\t3 \\t4 \\t5 \\t6 \\t > 33094 root 20 0 17172Ki 5488Ki CPU23 23 0:00 = 0.04% top -HiSCazopid >=20 > I do not intend to try to find all examples of characters that > cause problems but used to not cause problems. >=20 > =46rom what I've seen, cursor positioning escape character sequences > seem to be sent through and cause overwrites at arbitrary places > on screen, based on the escape sequence content. There are command > lines around that contain such sequences. So I sometimes see the > first few lines of top's output have garbage text from commands > that were listed below at some point overwriting the top text. >=20 > Part of what is going on is top avoiding rewriting characters > that its tracking indicates have not been updated. When the > actual display and that supposed-tracking mismatch, the > display ends up wrong when updated (bad text continues to > display). >=20 > The text in commands should not make "top -a" output mess up > the display of other lines in top's output, nor of other > top output fields on the same line. In my view, if some usage > contexts need otherwise, it should take an extra command line > option to put top in a mode that might do such things. The > default behavior should strictly avoid having such things > happen. I accidentally had a ^M instead of a ^H (backspace) at one position in my backspace example. Removing that carriage return produced: 33345 root 98 0 12764Ki 0\\n20Ki CP1\\n 82\\n:20 99.99% = 4\\n-HiS5\\npid 6\\n 7\\n 8\\n \\t0 \\t1 \\t2 \\t3 = \\t4 \\t5 \\t6 \\t7 \ 33094 root 20 0 17172Ki 5620Ki CPU24 24 0:02 0.04% = top -HiSCazopid And I tried: # tr = '\a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z\0\1\2\3\4\5\6\7\8\9'= = '\9\8\7\6\5\4\3\2\1\0\q\w\e\r\t\y\u\i\o\pa\s\d\f\g\h\j\jk\l\z\x\c\v\b\n\m'= < /dev/zero > /dev/null This seems to have worked as desired: truncating the tar -a output for the tr process the end of the tar line, with: \\7\\6\\5 No other lines were messed up. I also tried just control-K (Vertical Tab) sequences and it resulted in: 33417 root 103 0 12764Ki 2420Ki CPU10 10 1:03 99.96% = tr \v\v\v\v\v\v\v\v\v \v\v\v\v\v\v\v\v\v Similarly control-L (Form Feed) characters resulted in: 33429 root 102 0 12764Ki 2420Ki CPU12 12 0:31 99.99% = tr \f\f\f\f\f\f\f\f \f\f\f\f\f\f\f Similarly DEL characters resulted in: 33456 root 93 0 12764Ki 2420Ki CPU15 15 0:12 99.99% = tr = \177\177\177\177\177\177\177\177\177\177\177\177\177\177\177\177\177\177\1= 77\177\177\177\177\177\177\177 \177\177\177\177\17 (truncating at the end of top display line). QUOTE VIS_SAFE Only encode "unsafe" characters. Unsafe means control = char- acters which may cause common terminals to perform = unexpected functions. Currently this form allows space, tab, = newline, backspace, bell, and return -- in addition to all = graphic characters -- unencoded. END QUOTE If VIS_SAFE is avoided, it might be that space would end up encoded = instead of unencoded. that would not be good. But it does seem that encoding or replacing tab, newline, backspace, = bell, and return would be more appropriate than what now happens. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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