Undefined reference to SSL_library_init and SSL_load_error_strings

Question

I am implementing a OpenSSL code and have already included required header files but still I am getting errors like *

undefined reference to SSL

Answer 1

ldd libssl.so -> libcrypto.so.1.1 => not found

sudo ln -s /usr/local/lib64/libcrypto.so.1.1 /usr/lib64/libcrypto.so.1.1

libcrypto.so.1.1 => /lib64/libcrypto.so.1.1 (0x00007f17d46c7000)

Answer 2

For me this meant to install

 apt install libssl1.0-dev

Answer 3

Link against libssl and libcrypto. Your LDFLAGS and LDLIBS would be as follows. Order matters for LDLIBS:

LDFLAGS = -L/usr/local/ssl/lib
LDLIBS = -lssl -lcrypto

Don't worry about adding the "lib" in front of library name, or the "so" or "a" suffix. The linker will do it for you.

If you are building from the command line, then you would use the following. Again, order matters.

gcc foo.c -o foo.exe -L/usr/local/ssl/lib -lssl -lcrypto

If you are using the system's OpenSSL, then you can omit -L/usr/local/ssl/lib.

Answer 4

These methods are deprecated in OpenSSL 1.1. You don't need to use it more. You can just remove it. More info in OpenSSL manual.