This is a kindly hint that libguestfs-1:1.45.1-4.fc35 still uses PCRE library which has been superseded with PCRE2 project by PCRE upstream in 2015. PCRE upstream considers PCRE obsolete now and does not devote any resources to PCRE except of critical bugs. Please consider porting libguestfs from PCRE to PCRE2.
Interesting - I didn't know anything about this. We use the C API, although nothing very complicated about it. However I cannot find any documentation on migration or the differences between the APIs. It seems as if most of the symbols have gone from pcre|PCRE -> pcre2|PCRE2.
There is no migration guide. The basic approach remains the same, mostly only the prefix has changed. But there are slight differences, some data structures became opaque, some functions gained a new argument for a memory allocator to improve thread safety, API for an optional just-in-time matching was reworked, data types for Unicode code points and their UTF encoding were unified. I recommend you going through your code and checking the PCRE2 manual pages to see whether the functions differ. Again, there is pcre2demo(3) manual with an example application and pcre2api(3) with an index of the functions.
That was a bunch of busy-work, but here you go: https://github.com/libguestfs/libguestfs/commit/82493579f38f39769861f31403ccfb8e97b41f96 Will be fixed in libguestfs 1.45.2.
Thank you very much.