Undefined symbol reference, what could it be?

Question

OpenSSL

When compiling the RSA implementation code in qt, it gives two errors, I can’t figure out what the point is.
/openssl/libcrypto.a(dso_dlfcn.o): undefined symbol reference "[email protected]@GLIBC_2.2.5"
/lib/x86_64-linux-gnu/libdl.so.2:-1: error: error adding symbols: DSO missing from command line

Answer 1

Try to specify in *.pro file:
LIBS += -ldl