Linux c++ error: undefined reference to 'dlopen'

user_101375 0
Viewed 215678

I work in Linux with C++ (Eclipse), and want to use a library. Eclipse shows me an error:

undefined reference to 'dlopen'

Do you know a solution?

Here is my code: 

#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>

int main(int argc, char **argv) {
    void *handle;
    double (*desk)(char*);
    char *error;

    handle = dlopen ("/lib/CEDD_LIB.so.6", RTLD_LAZY);
    if (!handle) {
        fputs (dlerror(), stderr);
        exit(1);
    }

    desk= dlsym(handle, "Apply");

    if ((error = dlerror()) != NULL)  {
        fputs(error, stderr);
        exit(1);
    }

    dlclose(handle);
}
eclipse linux c++
12 Answers

You have to link against libdl, add

-ldl

to your linker options

user_1063670

this doesn't work:

gcc -ldl dlopentest.c

But this does:

gcc dlopentest.c -ldl

That's one annoying "feature" for sure

I was struggling with it when writing heredoc syntax and found some interesting facts. With CC=Clang, this works:

$CC -ldl -x c -o app.exe - << EOF
#include <dlfcn.h>
#include <stdio.h>
int main(void)
{
  if(dlopen("libc.so.6", RTLD_LAZY | RTLD_GLOBAL))
    printf("libc.so.6 loading succeeded\n");
  else
    printf("libc.so.6 loading failed\n");
  return 0;
}
EOF

./app.exe

as well as all of these:

  • $CC -ldl -x c -o app.exe - << EOF
  • $CC -x c -ldl -o app.exe - << EOF
  • $CC -x c -o app.exe -ldl - << EOF
  • $CC -x c -o app.exe - -ldl << EOF

However, with CC=gcc, only the last variant works; -ldl after - (the stdin argument symbol).

user_8639800

I was using CMake to compile my project and I've found the same problem.

The solution described here works like a charm, simply add ${CMAKE_DL_LIBS} to the target_link_libraries() call

user_33635270

Try to rebuild openssl (if you are linking with it) with flag no-threads.

Then try to link like this:

target_link_libraries(${project_name} dl pthread crypt m ${CMAKE_DL_LIBS})
user_88672710

In earlier versions(~2.7) of GNU tool chain, glibc did not have direct interface to link loader(dlopen and dlsym functions), so you had to provide -ldl(libdl) at compile time. You don't have to do that anymore with latest glibc version. Just include <dlcfn.h> and you are good to go.

user_27390180
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