When building libprocess against libevent and openssl 1.1, the results are deprecation warnings;
../3rdparty/libprocess/src/openssl.cpp:764:39: warning: 'ASN1_STRING_data' is deprecated [-Wdeprecated-declarations]
/usr/include/openssl/asn1.h:553:1: note: 'ASN1_STRING_data' has been explicitly marked deprecated here
DEPRECATEDIN_1_1_0(unsigned char *ASN1_STRING_data(ASN1_STRING *x))
/usr/include/openssl/opensslconf-x86_64.h:122:34: note: expanded from macro 'DEPRECATEDIN_1_1_0'
# define DEPRECATEDIN_1_1_0(f) DECLARE_DEPRECATED(f)
/usr/include/openssl/opensslconf-x86_64.h:96:56: note: expanded from macro 'DECLARE_DEPRECATED'
# define DECLARE_DEPRECATED(f) f __attribute__ ((deprecated));
These warnings are benign and can get ignored for now, as long as no warning to error escalation is active. For successful builds we need to activate disable-werror for autotools - cmake builds do not escalate warnings to errors by default.
We should still fix those warnings, likely by adapting towards openssl1.1 via preprocessor/define gates like;
#if OPENSSL_VERSION_NUMBER < 0x10100000L
[leave code as is]
[add variant that does not rely on deprecated ASN1_STRING_data]