Subject: bug#75569: 30.0.93; Large /proc/* file are read incompletely

From: Eli Zaretskii <[email-masked]>
Date: Wed, 15 Jan 2025 17:07:56 +0200

> Cc: [email-masked]
> From: Juri Linkov <[email-masked]>
> Date: Wed, 15 Jan 2025 09:19:10 +0200
> 
> > When opening a large file in /proc/* like /proc/cpuinfo in Emacs via
> > find-file, the buffer content is incomplete, when comparing the output
> > to the output produced by /bin/cat. The Eshell command eshell/cat has
> > the same problem.The proc file system doesn't report file sizes since
> > the files are dynamically generated. ls -l /proc/cpuinfo reports size 0.
> > Emacs doesn't handle this well, limiting its reads to 16KiB.
> >
> > In Eshell:
> >
> > cat /proc/cpuinfo > #<buffer bug>  ==> truncated buffer (exactly 16KiB)
> > *cat /proc/cpuinfo > #<buffer bug> ==> complete buffer (larger than 16KiB)
> 
> Strange, bug#9800 was closed as fixed, but I confirm the buffer is still
> truncated.

It was closed because it was fixed back then.  But maybe commits
8650b3308dd and/or 3fb2c174d3a7 broke that later?

The /proc/cpuinfo file on the system to which I have access is smaller
than 16KB, so could someone who can access a larger cpuinfo file
please see if those commits broke the fix, or maybe bisect?

Adding Paul in case he has comments or suggestions.