Re: [dev] Miscellaneous sbase issues

From: koneu <koneu93_AT_googlemail.com>
Date: Mon, 27 Apr 2015 10:21:05 +0200

On April 27, 2015 3:24:18 AM CEST, Michael Forney <mforney_AT_mforney.org> wrote:
>Hi suckless,
>
>I came across some issues in sbase whose solution wasn't immediately
>apparent:
>
>printf
>------
>Ignores flag characters '#', '0', '-', ' ', and '+', but is labeled as
>POSIX compliant and complete, so this is presumably unintentional.
>
>"git am" breaks without this functionality.
>
>tar
>---
>Since fb1595a69c091a6f6a9303b1fab19360b876d114, tar calls remove(3) on
>directories before extracting them. I'm not sure that it is reasonable
>for tar to do this because users may want to re-extract archives, or
>extract archives on top a directory structure that already exists.
>Additionally, it is fairly common to find tar archives containing the
>"." directory (possibly with a trailing '/'), which were constructed
>using "tar -cf foo.tar .".
>
>cat, tee
>--------
>These utilities read from stdin using fread(3) into a buffer of size
>BUFSIZ. However, fread will read until it fills up the entire buffer
>(or
>hits EOF) before returning, causing noticeable delay when the input
>comes from other programs or scripts.
>
>To demonstrate this problem, compare the output of these commands:
>
> for i in $(seq 500) ; do printf 0123456789abcdef ; sleep 0.005 ; done
>for i in $(seq 500) ; do printf 0123456789abcdef ; sleep 0.005 ; done |
>cat
>for i in $(seq 500) ; do printf 0123456789abcdef ; sleep 0.005 ; done |
>tee
>
>I considered fixing this by making the concat function take an fd
>instead and make a single call to read(2), but this causes problems for
>sponge, which uses a FILE * obtained from tmpfile(3) as both output and
>input for concat. We could also use mkstemp(3) to return a file
>descriptor, and use a FILE * from fdopen for writing, and the file
>descriptor for reading, but this seems unclean to me.
>
>Another option would be to use fgetc and fputc for the concat
>implementation, and let libc take care of the buffering. I'm not sure
>if
>this has any performance implications.
>
>
>Thanks everyone for their work on sbase! It really has come a long way
>in the last 6 months.

Firstly, patch..?
For cat and tee fgets might be more appropriate.
Received on Mon Apr 27 2015 - 10:21:05 CEST