How to fix C warning: implicit declaration of function 'dlsym'

Problem:

You have C code like

example.txt

dlsym(RTLD_NEXT, 'myfunc');
```c {filename="main.c"}

but when you try to compile it you see a warning message like

```plaintext {filename="dlsym_warning.txt"}
main.c: In function ‘main’:
main.c:3:5: warning: implicit declaration of function ‘dlsym’ [-Wimplicit-function-declaration]
     dlsym(RTLD_NEXT, 'myfunc');

dlsym(RTLD_NEXT, 'myfunc');
```c {filename="main.c"}

but when you try to compile it you see a warning message like

```plaintext {filename="dlsym_warning.txt"}
main.c: In function ‘main’:
main.c:3:5: warning: implicit declaration of function ‘dlsym’ [-Wimplicit-function-declaration]
     dlsym(RTLD_NEXT, 'myfunc');

Solution

Add

main_fixed.c

#include <dlfcn.h>

#include <dlfcn.h>

at the top of the source file where the error occured. This will include both dlopen, dlsym and related definitions like RTLD_NEXT.

Check out similar posts by category: C/C++, GCC Errors

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