This document describes how libcrypto was packaged for build2. In particular,
this understanding will be useful when upgrading to a new upstream version.
See ../README-DEV for general notes on OpenSSL packaging.

Symlink the required upstream files and directories into libcrypto/:

$ ln -s ../../upstream/{crypto,include,e_os.h} libcrypto

Create libcrypto/downstream/openssl/opensslconf.h including upstream's
opensslconf.h, auto-generated for the current platform. Similarly, create
libcrypto/downstream/crypto/{bn_conf.h,dso_conf.h}. Also define in
opensslconf.h some common macros to avoid defining them via the -D
preprocessor option (see libcrypto/buildfile for details). Note that
opensslconf.h is included into all public headers and, presumably, all source
files.

Create libcrypto/buildinf-body.h.in using the upstream's auto-generated
buildinf.h as a pattern. Create libcrypto/downstream/crypto/buildinf.h,
replacing the upstream's auto-generated header and including our own
auto-generated buildinf-body.h. Such a proxying is required for the headers
auto-generating machinery to work properly (see
libcrypto/downstream/crypto/buildinf.h for details).

Copy upstream's auto-generated libcrypto.map and libcrypto.def into libcrypto/.
Comment out the "LIBRARY libcrypto-1_1-..." line in libcrypto.def.

Start with compiling all source files and then iteratively exclude those that
cause compilation/linking problems. During this process grep through
build.info files in the file-in-question directories and
../../upstream/Configurations/00-base-templates.conf file they refer into (via
the $target{<key>} variables) to make sure that the source file should really
be omitted in our setup.

Figure out libssl-specific headers in libcrypto/openssl/ and disable their
installation. First, you can exclude headers used for building libcrypto (which
is assumed to already be built in source tree):

$ cat `find libcrypto/crypto/ -name '*.o.d'` | sed -n -r -e 's%^.+/include/openssl/([^/]+)$%\1%p' | sort -u >crypto.tmp
$ find libcrypto/include/openssl/ -name '*.h' | sort | sed -n -r -e 's%.+/([^/]+)$%\1%p' >openssl.tmp
$ comm -13 crypto.tmp openssl.tmp && rm crypto.tmp openssl.tmp

The above commands result in:

asn1_mac.h
dtls1.h
ecdh.h
ecdsa.h
mdc2.h
pem2.h
srtp.h
ssl2.h
ssl3.h
sslerr.h
ssl.h

This set can be reduced to just:

dtls1.h
srtp.h
ssl2.h
ssl3.h
sslerr.h
ssl.h