[FFmpeg-devel] [PATCH] Fix build with LibreSSL

[Michael Forney]

On 10/29/16, Matt Oliver <protogonoi at gmail.com> wrote:
> This also seems a bit odd, why is libreSSL setting an openssl version
> number of 1.1.0 or higher when it doesnt actually conform to the
> corresponding openssl version. LibreSSl setting the openssl version number
> to 2.0.0 seems to be problematic and causes problems not just for ffmpeg.
> Of course theres not much we can do about that but perhaps an alternative
> to Michaels suggestion would be to just add a single check near the top of
> the file that checks for libressl and then redefines the openssl version to
> the api libressl actually supports. i.e.
>
> #ifdef LIBRESSL_VERSION_NUMBER
> #undef OPENSSL_VERSION_NUMBER
> #define OPENSSL_VERSION_NUMBER 0x1000107fL
> #endif
>
> This I believe is what some other projects have done to avoid this issue
> and is rather simple to add and prevents further clutter in our configure.
> I dont have any preference between this and the other suggestion, im just
> providing some alternatives. The above is pretty simple so if it works for
> you i can write up a patch for that pretty easily.

I'm not sure why libressl sets OPENSSL_VERSION_NUMBER to 0x20000000L.
Maybe so that they can pick and choose which openssl APIs to implement
(rather than everything up through some version)?

I'm fine with any of the suggested approaches. I just went with
!defined(LIBRESSL_VERSION_NUMBER) in my original patch because that's
what I've seen projects like curl, wpa_supplicant, and openvpn do. It
also seems to be what openbsd is doing itself with patches in its
ports tree (xca, stunnel, postfix).