main.c

#include <assert.h>
#include <dlfcn.h>

int main() {
    void *handle = dlopen("./test.so", RTLD_NOW);
    assert(handle);
    void (*memzero)(void* src, size_t len) = dlsym(handle, "memzero");
    assert(memzero);
    char c;
    memzero(&c, 1);
    assert(!dlclose(handle));
}

Makefile

CFLAGS = -g
LD = ld.lld
LDLIBS = /lib/x86_64-linux-gnu/libdl.so.2 /lib/x86_64-linux-gnu/libc.so.6

default: main test.so

clean:
	rm main test.so main.o test.o

main: main.o

test.so: test.o
	$(LD) -shared -o $@ $^ $(LDLIBS)

test.c

#include <string.h>

void memzero(void* src, size_t len) {
    static void* (*const volatile memsetv)(void*, int, size_t) = &memset;
    memsetv(src, 0, len);

}