Stray characters beyond COLUMNS with -# after a redirect

[arachsys]

I did this

Fetch a file via a redirect with -# and -L. Specify a smallish COLUMNS to make the symptoms clearer:

# COLUMNS=40 curl -o /dev/null -L -# https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.10.tar.xz
################                   48.8%###=-

Capturing the output with COLUMNS=32 (for a multiple of 16) and hexdumping, it's a bit clearer what's happened:

00000000  23 23 4f 3d 2d 20 20 20  20 20 20 20 20 20 20 20  |##O=-           |
00000010  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000020  0d 0d 23 23 23 23 23 23  23 23 23 23 23 23 23 23  |..##############|
00000030  23 23 23 23 23 23 23 23  23 23 23 20 31 30 30 2e  |########### 100.|
00000040  30 25 23 23 23 3d 2d 20  20 20 20 20 20 20 20 20  |0%###=-         |
00000050  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000060  20 20 0d 0d 20 20 20 20  20 20 20 20 20 20 20 20  |  ..            |
00000070  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000080  30 2e 31 25 0d 20 20 20  20 20 20 20 20 20 20 20  |0.1%.           |
00000090  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
000000a0  20 30 2e 35 25 0d 20 20  20 20 20 20 20 20 20 20  | 0.5%.          |
000000b0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
000000c0  20 20 31 2e 30 25 0d 20  20 20 20 20 20 20 20 20  |  1.0%.         |
000000d0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
000000e0  20 20 20 31 2e 34 25 0d  20 20 20 20 20 20 20 20  |   1.4%.        |
000000f0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000100  20 20 20 20 31 2e 39 25  0d 20 20 20 20 20 20 20  |    1.9%.       |
00000110  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000120  20 20 20 20 20 32 2e 34  25 0d 20 20 20 20 20 20  |     2.4%.      |
00000130  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |

There seem to be two \r characters before the 100% bar and none after it, rather than one before it and one after.

I can only reproduce this behaviour with a redirect and -L.

I expected the following

Progress bar output restricted to COLUMNS characters per line, without stray characters beyond this point, presumably a single \r before the ###=- is output.

curl/libcurl version

$ curl --version
curl 8.8.0 (x86_64-arachsys-linux-musl) libcurl/8.8.0 LibreSSL/3.9.2 zlib/1.3.1 zstd/1.5.6 libpsl/0.21.5 nghttp2/1.62.1
Release-Date: 2024-05-22
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns mqtt pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
Features: alt-svc AsynchDNS HSTS HTTP2 HTTPS-proxy IPv6 Largefile libz NTLM PSL SSL threadsafe UnixSockets zstd

operating system

My own machine, on which I originally spotted this:

$ uname -a
Linux xi 6.10 #1 SMP PREEMPT Wed Jul 17 15:55:48 BST 2024 x86_64 GNU/Linux

However, I have also reproduced this with the Debian packaged curl 7.88.1-10+deb12u5 on a glibc 2.36.9 machine, to confirm it's not a bug in musl stdio.h.

[bagder]

Thanks for showing how to easily reproduce.