OpenSSL 4.0 is in experimental. This package fails to build against it:

| cc -o buckets/ssl_buckets.o -c -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/build/reproducible-path/serf-1.3.10=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -std=c89 -Wdeclaration-after-statement -Wmissing-prototypes -Wall -O2 -isystem /usr/include/mit-krb5 -Wdate-time -D_FORTIFY_SOURCE=2 -DNDEBUG -DOPENSSL_NO_STDIO -DLINUX -D_REENTRANT -D_GNU_SOURCE -DSERF_HAVE_GSSAPI -I. -I/usr/include/apr-1.0 -I/usr/include -I/usr/include buckets/ssl_buckets.c
| buckets/ssl_buckets.c: In function 'get_subject_alt_names':
| buckets/ssl_buckets.c:570:41: error: invalid use of incomplete typedef 'ASN1_IA5STRING' {aka 'struct asn1_string_st'}
|   570 |                         strlen(nm->d.ia5->data) != nm->d.ia5->length)
|       |                                         ^~
| buckets/ssl_buckets.c:570:61: error: invalid use of incomplete typedef 'ASN1_IA5STRING' {aka 'struct asn1_string_st'}
|   570 |                         strlen(nm->d.ia5->data) != nm->d.ia5->length)
|       |                                                             ^~
| buckets/ssl_buckets.c:573:77: error: invalid use of incomplete typedef 'ASN1_IA5STRING' {aka 'struct asn1_string_st'}
|   573 |                         p = pstrdup_escape_nul_bytes((const char *)nm->d.ia5->data,
|       |                                                                             ^~
| buckets/ssl_buckets.c:574:63: error: invalid use of incomplete typedef 'ASN1_IA5STRING' {aka 'struct asn1_string_st'}
|   574 |                                                      nm->d.ia5->length,
|       |                                                               ^~
…

Full buildlog
https://breakpoint.cc/openssl-rebuild/logs-4/attempted/serf_1.3.10-3_amd64-2026-04-19T09:36:28Z

Sebastian

Hello,

Bug #1138352 in serf reported by you has been fixed in the
Git repository and is awaiting an upload. You can see the commit
message below and you can check the diff of the fix at:

https://salsa.debian.org/jamessan/serf/-/commit/5b64e3af201a8d77cc2533ca66ea0c5f549591a8
------------------------------------------------------------------------
Backport upstream patch to fix building with OpenSSL 4.x

Closes: #1138352
Signed-off-by: James McCoy <jamessan@debian.org>
------------------------------------------------------------------------

(this message was generated automatically)
-- 
Greetings

https://bugs.debian.org/1138352

Dear Maintainer,

I noticed on Ubuntu that autopkgtests are failing with openssl 4 and it does not seem to be addressed in the git commit. full log: https://autopkgtest.ubuntu.com/results/autopkgtest-stonking/stonking/amd64/s/serf/20260730_092108_391b3@/log.gz

We believe that the bug you reported is fixed in the latest version of
serf, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1138352@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
James McCoy <jamessan@debian.org> (supplier of updated serf package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Tue, 04 Aug 2026 19:52:39 -0400
Source: serf
Architecture: source
Version: 1.3.10-4
Distribution: unstable
Urgency: medium
Maintainer: James McCoy <jamessan@debian.org>
Changed-By: James McCoy <jamessan@debian.org>
Closes: 1138352
Changes:
 serf (1.3.10-4) unstable; urgency=medium
 .
   * Backport upstream patch to fix building with OpenSSL 4.x (Closes: #1138352)
   * Skip test_ssltunnel_basic_auth_server_has_keepalive_off test
   * Remove Priority, since optional is the default
   * Remove Rules-Requires-Root, since no is the default
   * Declare compliance with Policy 4.7.4
   * d/tests/control: Change pkg-config -> pkgconf
   * Update to debhelper-compat 14
Checksums-Sha1:
 9ddc3668f89feec472ece608a1f0994096148fbb 2507 serf_1.3.10-4.dsc
 886f29f59ff0ea18440bb0796bbb990640f9cd61 69524 serf_1.3.10-4.debian.tar.xz
 5e2933eff59932909a14147ab470e6ad019fe92b 608064 serf_1.3.10-4.git.tar.xz
 a1709a85ec8182ece3e57e2d78bb59dab55e4d97 17544 serf_1.3.10-4_source.buildinfo
Checksums-Sha256:
 7a06235a410e90c7f8b595f36acd14050d842d06ef2e00de4f1dc1dad7a7003d 2507 serf_1.3.10-4.dsc
 9b54e5c70c30edb570b5223f64fe60b77c0631b480f328b9d4ed16de6e83291f 69524 serf_1.3.10-4.debian.tar.xz
 14705248c818b59422f3d51fc6b5e91e934c55677c67d14ab2e09054b835d9e4 608064 serf_1.3.10-4.git.tar.xz
 05e33d23f5678bd09131c088f4e4c0e82dc3a1b036c55588ae375e875fb00db1 17544 serf_1.3.10-4_source.buildinfo
Files:
 07dda0d71c60c6f1d6575eeba1e3dcce 2507 libs optional serf_1.3.10-4.dsc
 15b8b117d9eac9130c90fc9b38a22d48 69524 libs optional serf_1.3.10-4.debian.tar.xz
 c0b235b92ac1964604ba698b1de0461e 608064 libs None serf_1.3.10-4.git.tar.xz
 700eec5856f0b30e95b04cf1a3ec0520 17544 libs optional serf_1.3.10-4_source.buildinfo
Git-Tag-Info: tag=c3440b19b47a5c1f1d1c0632f95b4c01c90f457b fp=91bfbf4d6956bd5df7b72d23dfe691ae331ba3db
Git-Tag-Tagger: James McCoy <jamessan@debian.org>
-----BEGIN PGP SIGNATURE-----
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=B1zg
-----END PGP SIGNATURE-----