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

You have to link against libdl, add

-ldl

to your linker options

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

@Masci is correct, but in case you're using C (and the gcc compiler) take in account that this doesn't work:

gcc -ldl dlopentest.c

But this does:

gcc dlopentest.c -ldl

Took me a bit to figure out...

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).