$ ./configure
$ gmake
[...]
cc -pthread  -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -fPIC -c ./Modules/_ssl.c -o Modules/_ssl.o
./Modules/_ssl.c:4800:18: error: call to undeclared function 'X509_OBJECT_set1_X509'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
            ok = X509_OBJECT_set1_X509(ret, X509_OBJECT_get0_X509(obj));
                 ^
./Modules/_ssl.c:4800:18: note: did you mean 'X509_OBJECT_get0_X509'?
/usr/include/openssl/x509_vfy.h:285:7: note: 'X509_OBJECT_get0_X509' declared here
X509 *X509_OBJECT_get0_X509(const X509_OBJECT *xo);
      ^
./Modules/_ssl.c:4804:18: error: call to undeclared function 'X509_OBJECT_set1_X509_CRL'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
            ok = X509_OBJECT_set1_X509_CRL(
                 ^
./Modules/_ssl.c:4804:18: note: did you mean 'X509_OBJECT_get0_X509_CRL'?
/usr/include/openssl/x509_vfy.h:286:11: note: 'X509_OBJECT_get0_X509_CRL' declared here
X509_CRL *X509_OBJECT_get0_X509_CRL(X509_OBJECT *xo);
          ^
./Modules/_ssl.c:4821:1: error: static declaration of 'X509_STORE_get1_objects' follows non-static declaration
X509_STORE_get1_objects(X509_STORE *store)
^
/usr/include/openssl/x509_vfy.h:296:24: note: previous declaration is here
STACK_OF(X509_OBJECT) *X509_STORE_get1_objects(X509_STORE *xs);
                       ^
./Modules/_ssl.c:4824:10: error: call to undeclared function 'X509_STORE_lock'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
    if (!X509_STORE_lock(store)) {
         ^
./Modules/_ssl.c:4827:11: error: call to undeclared function 'sk_X509_OBJECT_deep_copy'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
    ret = sk_X509_OBJECT_deep_copy(X509_STORE_get0_objects(store),
          ^
./Modules/_ssl.c:4827:9: warning: incompatible integer to pointer conversion assigning to 'struct stack_st_X509_OBJECT *' from 'int' [-Wint-conversion]
    ret = sk_X509_OBJECT_deep_copy(X509_STORE_get0_objects(store),
        ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./Modules/_ssl.c:4829:5: error: call to undeclared function 'X509_STORE_unlock'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
    X509_STORE_unlock(store);
    ^
1 warning and 6 errors generated.
gmake: *** [Makefile:3505: Modules/_ssl.o] Error 1