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Date: Thu, 16 Oct 2025 10:02:45 +1100
To: cygwin AT cygwin DOT com
Subject: Re: bash hangs when executing a script with a here document larger
 than 64 KiB
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From: Duncan Roe via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Duncan Roe <duncan_roe AT optusnet DOT com DOT au>
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On Sun, Oct 05, 2025 at 08:03:34AM +0200, cygwin wrote:
> On 10/5/2025 6:57 AM, Duncan Roe via Cygwin wrote:
> > If the bug is to persist, I suggest to munge psize.c:-
> >
> > | *** builtins/psize.c.bu Fri Aug 15 05:56:53 2008
> > | --- builtins/psize.c    Sun Oct  5 14:06:50 2025
> > | ***************
> > | *** 51,57 ****
> > |   sigpipe (sig)
> > |        int sig;
> > |   {
> > | !   fprintf (stderr, "%d\n", nw);
> > |     exit (0);
> > |   }
> > |
> > | --- 51,57 ----
> > |   sigpipe (sig)
> > |        int sig;
> > |   {
> > | !   fprintf (stderr, "%d\n", nw - 128);
> > |     exit (0);
> > |   }
> > |
> >
> > N.B. blank lines (after removing 1st 2 chars) have 2 trailing spaces.
> >
> > Cheers ... Duncan.
> >
> Subtracting 128 (the granularity of the test code), seems very arbitrary and
> kludgy.

Kludgy?? It's the expected result when you write that number of bytes.

Anyway, it's a *tested* and *working* 1-line fix. Any 1-line fix is a good fix.

>
> An obvious simplification is to disable SIGPIPE and use a loop that ends
> when 0or -1
> is returned, like this:
>
> /* The following code was written directly in the mail and not tested */

Clearly not tested 🙄
>
>   /* TODO: ignore SIGPIPE instead of setting a handler */
>
>   nw = 0;
>   for(;;)
>     {
>       i = write (1, buf, 128);
>       if (i <= 0)
>         break;
>       nw += i;
>     }
>   /* These are the error codes in the POSIX write(3P) man page
>    * associated with hitting the pipe limit or similar,
>    * maybe this code should accept a few more error codes in
>    * real world use for this.
>    */
>   if (errno == EPIPE || errno == ENOSPC || errno == EAGAIN ||
>       errno == EFBIG || errno == ENOBUFS)
>     fprintf (stderr, "%d\n", nw);
>   else
>     perror (argv[0]);

Doesn't work. As per my previous email, the over-capacity write only returns on
receipt of a signal, but before the signal is delivered.

It *might* work if the pipe were made non-blocking, but that's a lot of code
churn compared with a 1-liner.

>
> Another simplification would be for psize.c to open its own pipe and
> simply never read from it, thus removing any dependency on how the build
> time shell and sleep programs handle the pipe.

Won't work, see above.
>
> --
> Jakob Bohm, CIO, partner, WiseMo A/S. https://www.wisemo.com
> Transformervej 29, 2860 Soborg, Denmark. direct: +45 31 13 16 10
> <tel:+4531131610>
> This message is only for its intended recipient, delete if misaddressed.
> WiseMo - Remote Service Management for PCs, Phones and Embedded

Cheers ... Duncan.





























































































































































































































































































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