make fails to compile, undefined reference to `EVP_DigestUpdate

Question

I am trying to install an open source project on my ubuntu 13:04 but the make process fails on a method in a class called updateDB.c. During compilation, i have this error :

updateDB.o: In function `update_cache_hash':
/usr/local/src/bgpinspect-0.5/src/updateDB.c:142: undefined reference to `EVP_DigestUpdate'
/usr/local/src/bgpinspect-0.5/src/updateDB.c:143: undefined reference to `EVP_DigestFinal_ex'
collect2: error: ld returned 1 exit status
make[1]: *** [BGPdb] Error 1
make[1]: Leaving directory `/usr/local/src/bgpinspect-0.5/src'
make: *** [all] Error 2

This is the method update_cache_hash that fails :

static uint16_t update_cache_hash( char *buff, int size ) {
    unsigned char md_hash[EVP_MAX_MD_SIZE];
    unsigned int md_len;
    uint16_t hash;

    EVP_DigestUpdate(&global_table.ctx, buff, size );
    EVP_DigestFinal_ex(&global_table.ctx, md_hash, &md_len);

    if ( md_len < 2 ) {
        ps_log( PS_LOG_ERROR, "EVP_DigestFinal_ex returned a short hash.\n" );
        return 0;
    }

    hash = ( (uint16_t) md_hash[md_len - 2] << 8 ) | md_hash[md_len - 1];
    hash = UPDATE_CACHE_MASK( hash );

    return hash;
}

The top of this class has an include statement

#include <openssl/evp.h>

I have openssl installed on my computer alongside libssl-dev ; I can't figure out why it gives that error since i am new with c and static links etc. I have evp.h on this path : /usr/include/openssl/evp.h

So how may i change the makefile or configure to maybe fix this issue ? because it seems make can't see this path /usr/include/openssl/evp.h

Answer 1

The undefined reference error is a linker error, so it appears that gcc is finding /usr/include/openssl/evp.h but the linker is unable to find the library that has the EVP_DigestUpdate and EVP_DigestFinal_ex functions.

I'd check that the makefile in question has an -lcrypto argument and that make is finding the right libcrypto on your system.

Answer 2

The linker cannot find the libssl functions. You need to link libssl to your project.

There are suggestions in this SO article: Undefined reference to t1sl_steup_key_block when linking OpenSSL

For example, in your makefile, you'd add -lssl:

gcc somefile.c -o someprogram -lssl