OpenSSL 4.0 is in experimental. This package fails to build against it:
| tlscommon.c: In function 'subjectaltnameaddr':
| tlscommon.c:339:8: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
|   339 |     ex = X509_get_ext(cert, loc);
|       |        ^
| tlscommon.c:350:21: error: implicit declaration of function 'ASN1_STRING_data'; did you mean 'ASN1_STRING_set0'? [-Wimplicit-function-declaration]
|   350 |         v = (char *)ASN1_STRING_data(gn->d.ia5);
|       |                     ^~~~~~~~~~~~~~~~
|       |                     ASN1_STRING_set0
| tlscommon.c:350:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
|   350 |         v = (char *)ASN1_STRING_data(gn->d.ia5);
|       |             ^
| tlscommon.c: In function 'subjectaltnameregexp':
| tlscommon.c:375:8: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
|   375 |     ex = X509_get_ext(cert, loc);
|       |        ^
| tlscommon.c:386:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
|   386 |         v = (char *)ASN1_STRING_data(gn->d.ia5);
|       |             ^
| tlscommon.c: In function 'cnregexp':
| tlscommon.c:422:8: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
|   422 |     nm = X509_get_subject_name(cert);
|       |        ^
| tlscommon.c:428:11: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
|   428 |         e = X509_NAME_get_entry(nm, loc);
|       |           ^
| tlscommon.c:429:11: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
|   429 |         t = X509_NAME_ENTRY_get_data(e);
|       |           ^
| tlscommon.c:430:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
|   430 |         v = (char *) ASN1_STRING_data(t);
|       |             ^
| make[3]: *** [Makefile:445: libradsec_radsecproxy_la-tlscommon.lo] Error 1

Full buildlog
https://breakpoint.cc/openssl-rebuild/logs-4/attempted/libradsec_0.0.5-5.1_amd64-2026-04-19T14:07:16Z

Sebastian