dlsym import method once for subsequent use - c

Question

Please consider the below code
shared.c
#include <stdio.h>
void printCharArray(char *someArray){
if (!someArray){
printf("someArray is null!\n");
} else {
printf("Array is %s\n", someArray);
}
}
and question.c:
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#define LIB "/tmp/some.so"
void *handle = 0;
void localfunc();
int main(){
handle = dlopen(LIB, RTLD_LAZY);
if (!handle){
fprintf(stderr, "dlopen err\n");
exit(1);
}
dlerror();
void (*printCharArray)() = dlsym(handle, "printCharArray");
char *err = dlerror();
if (err){
fprintf(stderr, "%s\n", err);
exit(1);
}
printCharArray(); // some work
localfunc();
}
void localfunc(){
puts("localfunc");
dlerror();
void (*printCharArray)() = dlsym(handle, "printCharArray"); // <- This
char *err = dlerror();
if (err){
fprintf(stderr, "%s\n", err);
exit(1);
}
printCharArray(); // do some work in localfunc
}
Compile and run
2035 gcc -shared -o /tmp/some.so shared.c -fPIC
2036 gcc -ldl question.c
$ ./a.out
someArray is null!
localfunc
someArray is null!
Notice how in localfunc I call dlsym again to import "printCharArray" which was previously done in main(). I am looking to avoid this - how can I make this method available after the 1st import? (iow, how can I make my 1st import to be available as a fn prototype for use anywhere in question.c?)

Answer 1

Declare the function pointer as a global variable, rather than local to main().
Give it the correct parameter declaration so the call matches the definition. And then call it with an argument.
There's no point in calling dlerror() before calling dlsym(). And it doesn't do anything useful if you don't assign the result to something.
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#define LIB "/tmp/some.so"
void *handle = 0;
void localfunc();
void (*printCharArray)(char *);
int main(){
handle = dlopen(LIB, RTLD_LAZY);
if (!handle){
fprintf(stderr, "dlopen err: %s\n", dlerror());
exit(1);
}
printCharArray = dlsym(handle, "printCharArray");
if (!printCharArray) {
char *err = dlerror();
printf(stderr, "%s\n", err);
exit(1);
}
printCharArray(NULL); // some work
localfunc();
}
void localfunc(){
puts("localfunc");
printCharArray("something"); // do some work in localfunc
}