Accessing list of symbols in plugin

Question

i'm using libltdl in order to dynamically load plugin libraries. Been following this documentation, and after i call this

lt_dlhandle lt_dlopen (const char *filename)

i need to know what symbols are defined in this library. I need the list of symbols to pass it to

void * lt_dlsym (lt_dlhandle handle, const char *name)

Which requires a symbol name as an argument.

What is the way to get the lists of loadable exported symbols in my plugin?

Answer 1

Like said Matthieu M. in his comment, there is no native way to get a list of loaded symbols from a dynamic lib.

However, I usually use this workaround, which is to make your plugin declare the symbols in a container, and then to retrieve this container from your main program.

plugin.h

#include <set>
#include <string>

// call this method from your main program to get list of symbols:
const std::set<std::string> & getSymbols();

void MySymbol01();
bool MySymbol02(int arg1, char arg2);

plugin.c

#include "plugin.h"

class SymbolDeclarator {
    public:
    static std::set<std::string> symbols;
    SymbolDeclarator(const std::string & symbol) {
        symbols.insert(symbol);
    }
};

const std::set<std::string> & getSymbols() {
    return SymbolDeclarator::symbols;
}

#define SYMBOL(RETURN, NAME) \
    static const SymbolDeclarator Declarator##NAME(#NAME); \
    RETURN NAME

SYMBOL(void, MySymbol01)() {
    // write your code here
}

SYMBOL(bool, MySymbol02)(int arg1, char arg2) {
    // write your code here
}

I only see 2 issues with this solution:

1. to have a non-const static variable: symbols declared in plugin.c -> non thread-safe.
2. to have code executed before the main(), which is hardly debuggable.