Pointer to array of pointers to functions - c++

Question

The idea is to call different functions based on their index in table.
But line 27 generates the runtime error ((
I tried to fix but didn't succeed (((
Here's the simplified code:
#include <iostream>
void f1 (void) {
std::cout << "f1" << "\n";
}
void f2 (void) {
std::cout << "f2" << "\n";
}
typedef void (*fPtr[3])(void); // simple "[]" instead of "[3]" gets the compile error
class modeChanger {
public:
modeChanger (fPtr funcArray);
void op ();
private:
fPtr *_funcArray;
};
modeChanger::modeChanger (fPtr funcArray) {
_funcArray = (fPtr *) funcArray;
}
void modeChanger::op () {
(*_funcArray[0])();
(*_funcArray[1])(); // Line 27: this line generates a runtime error! Just comment it to get all work
}
void (*modeFuncArray[])(void) = {f1, f2, f2};
modeChanger *mode = new modeChanger (modeFuncArray);
int main() {
(*modeFuncArray[1])(); // Works fine
mode->op(); // generates a runtime error
return 0;
}
This works good:
(*_funcArray[0])();
as well as this:
(*modeFuncArray[1])();
but this generates a runtime error...
(*_funcArray[1])();
Seems that incrementing of _funcArray is incorrect for some reason.

Answer 1

fPtr *_funcArray; this is the pointer to array, not an array of pointers. You suppressed warnings with help of type casts. See bellow the fixed code.
#include <iostream>
void f1 (void) {
std::cout << "f1" << "\n";
}
void f2 (void) {
std::cout << "f2" << "\n";
}
typedef void (*fPtr)(void);
class modeChanger {
public:
modeChanger (fPtr *funcArray);
void op ();
private:
fPtr *_funcArray;
};
modeChanger::modeChanger (fPtr *funcArray) {
_funcArray = funcArray;
}
void modeChanger::op () {
(*_funcArray[0])();
(*_funcArray[1])(); // Line 27: this line generates a runtime error! Just comment it to get all work
}
void (*modeFuncArray[])(void) = {f1, f2, f2};
modeChanger *mode = new modeChanger (modeFuncArray);
int main() {
(*modeFuncArray[1])(); // Works fine
mode->op(); // generates a runtime error
return 0;
}

Answer 2

Applying #Someprogrammerdude's advice:
#include <iostream>
#include <array>
#include <functional>
void f1 (void) {
std::cout << "f1" << "\n";
}
void f2 (void) {
std::cout << "f2" << "\n";
}
using fPtr = std::function<void()>;
using fPtrs = std::array<fPtr, 3>;
class modeChanger {
public:
modeChanger (fPtrs funcArray);
void op ();
private:
fPtrs _funcArray;
};
modeChanger::modeChanger (fPtrs funcArray) : _funcArray(funcArray) { }
void modeChanger::op () {
_funcArray[0]();
_funcArray[1]();
}
int main() {
fPtrs modeFuncArray = {f1, f2, f2};
modeChanger mode(modeFuncArray);
modeFuncArray[1]();
mode.op();
return 0;
}
And thus instead of "hard to declare" C types, we have things as easy as int, and all is well.

Answer 3

as you use c++, you should use c++ features and not C, you should use <functional>
#include <iostream>
#include <functional>
void f1(void) {
std::cout << "f1" << "\n";
}
void f2(void) {
std::cout << "f2" << "\n";
}
typedef void(*fPtr[3])(void); // simple "[]" gets the compile error
class modeChanger {
public:
modeChanger(std::function<void(void)>* funcArray);
void op();
private:
std::function<void(void)> * _funcArray;
};
modeChanger::modeChanger(std::function<void(void)>* funcArray) {
_funcArray = funcArray;
}
void modeChanger::op() {
_funcArray[0]();
_funcArray[1](); // this line generates a runtime error! Just comment it to get all work
}
std::function<void(void)> modeFuncArray[] = { f1, f2, f2 };
modeChanger *mode = new modeChanger(modeFuncArray);
int main() {
modeFuncArray[1](); // Works fine
mode->op(); // generates a runtime error
return 0;
}