Well, that sounds like a challenge. Please let me know if I can help you in any way. I am running many Gentoo systems that use binary packages built on my own buildhost, therefor it is fairly easy for me to patch the current version of Bash and test it on some systems. Thanks in advance for your help.
* Thomas ________________________________ Von: Martin D Kealey <mar...@kurahaupo.gen.nz> Gesendet: Dienstag, 8. Oktober 2024 06:23 An: Martin D Kealey <mar...@kurahaupo.gen.nz> Cc: Thomas Oettli <thomas.oet...@sfs.com>; bug-bash <bug-bash@gnu.org> Betreff: [EXT] Re: read command sometimes misses newline on timeout CAUTION: This email originated from outside the SFS organization. Do not follow guidance, click links or open attachments unless you recognize the sender and know the content is safe. MAIL FROM: <@mar...@kurahaupo.gen.nz> Report as Spam / Check Mail<https://mail1.sfs.biz/pyquarantine.php?quarantine=orig&action=report_or_check&mailfrom=martin%40kurahaupo.gen.nz&id=20241008062330_84DA229C4B473> OK, running a similar test with instrumentation gets: $ time ( trap ' echo BANG ' SIGALRM ; while :; do printf TEST; sleep .00$((1+RANDOM%2)); echo; done | for ((r=100000 ;r>0; --r)) do line= ; read -t .002 line; rc=$?; [[ $line = TEST ]] ; echo "STATUS $rc $? $line" ; done ) |& sort | uniq -c 1 +# Hit read timeout SIGALRM, run from line 699 in ./read.def #+ STATUS 142 1 TES 1 +# Hit read timeout SIGALRM, run from line 72 in zread.c #+ STATUS 142 1 2 +# Hit read timeout SIGALRM, run from line 865 in ./read.def #+ STATUS 142 1 T 1 +# Hit read timeout SIGALRM, run from line 865 in ./read.def #+ STATUS 142 1 TES 16 +# Hit read timeout SIGALRM, run from line 913 in ./read.def #+ STATUS 142 0 TEST 1721 +# Hit read timeout SIGALRM, run from line 913 in ./read.def #+ STATUS 142 1 3 STATUS 0 0 TEST 32649 STATUS 0 1 34367 STATUS 142 0 TEST 31235 STATUS 142 1 2 STATUS 142 1 EST 2 STATUS 142 1 T real 3m21.411s user 1m14.054s sys 1m46.493s That's to say, that out of 100000 reads: * 0.003% had both `read` returning 0 and filling var with TEST. * 34.4% had `read returning non-zero but filling var with TEST. * 32.6% had `read` returning 0 but leaving var empty (which is presumably the delayed bare newline after previously filling the var with TEST but returning 142). * 1.7% were handled by `check_read_timeout()`, and all had read returning a status of 142 (and leaving var empty). I note that 1721+32649-34367=3 so I infer that the last 3 cases are interconnected: Of that 1.7% almost all were handled by this section of read.def: /* I don't think this clause ever tests true. */ if (skip_ctlnul && saw_escape && i == 1 && input_string[0] == CTLNUL) saw_escape = 0; /* Avoid dequoting bare CTLNUL */ input_string[i] = '\0'; check_read_timeout (); #if defined (READLINE) if (edit) free (rlbuf); #endif -Martin PS: I've since run other tests that confirm the association I noted above, but I didn't keep the output. I'll run them again if anyone wants to see a more precise demonstration.
