No reference to BIO-functions when linking OpenSSL

Question

I'm trying to compile a c-program with openssl-references. I'm using Linux Mint 17.1 and the development package "libssl-dev" is installed.

#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/ssl.h>
...

void send_smtp_request(BIO *bio, const char *req)
{
    BIO_puts(bio, req);
    BIO_flush(bio);
    printf("%s", req);     
}

If I compile the code with:

gcc -o client bio-ssl-smtpcli2.c

I get the this error:

/tmp/ccCHrti2.o: In function 'send_smtp_request':
bio-ssl-smtpcli2.c:(.text+0x1f):  undefined reference to 'BIO_puts'
bio-ssl-smtpcli2.c:(.text+0x3a):  undefined reference to 'BIO_ctrl'

Does someone have an idea how to fix this?

Possible duplicate of [Linking problem of OpenSSL library in existing C project](http://stackoverflow.com/questions/5700617/linking-problem-of-openssl-library-in-existing-c-project), [Linking OpenSSLs libcrypto in GCC](http://stackoverflow.com/q/18835219), [Errors that refer to a bunch of unresolved OpenSSL symbols that clearly exist?](http://stackoverflow.com/q/15318978), ... — jww, May 09 '15 at 22:13

score 17 · Accepted Answer · edited Jul 14 '16 at 18:13

17

I managed to compile your function by using :

gcc main.c -o main -I /usr/local/ssl/include -L /usr/local/ssl/lib -lssl -lcrypto -Wall

More explainations :

-I /usr/local/ssl/include adds /usr/local/ssl/include to the include search path.
-L /usr/local/ssl/lib adds /usr/local/ssl/lib to the library search path.
-lssl -lcrypto links libraries libcrypto and libssl
-lcrypto must follow -lssl becuase ld is a single pass linker
Wall enables all warnings.

My guess is that you are missing -lcrypto.

edited Jul 14 '16 at 18:13

jww

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answered May 09 '15 at 16:13

francis

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I got a new error: /usr/local/ssl/lib//libssl.a(ssl_lib.o): In function `SSL_clear': ssl_lib.c:(.text+0x19e): undefined reference to `COMP_CTX_free' – S1J0 May 11 '15 at 11:44
I found [this answer to the same problem](http://ubuntuforums.org/archive/index.php/t-985136.html) : try to put `-lssl` in front of `-lcrypto`. I changed my answer accordingly. – francis May 11 '15 at 11:51
Ok no errors anymore :) To complete the answer, I had to add -ldl – S1J0 May 11 '15 at 12:14

score 0 · Answer 2 · answered Apr 10 '23 at 02:33

0

put -lssl in front of -lcrypto the solved my issue, thanks!

answered Apr 10 '23 at 02:33

Sunding Wei

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No reference to BIO-functions when linking OpenSSL

2 Answers2