Call to static overloaded (class) function/method is ambiguous

Question

In my C++ class, I have two static methods, called getInstance.

The method declarations are as follows:

public: // +++ STATIC +++
    static CanCommunicator* getInstance(shared_ptr<ThreadState> state);
    static CanCommunicator* getInstance();

In a global function (required, because of legacy code), I'm calling a getter from the object:

auto tState = CanCommunicator::getInstance()->getThreadState();

The compiler (GCC 4.4.5) is giving me the following error:

CanCommunicator::getInstance is ambiguous
Candidates are:
CanCommunicator * getInstance()
CanCommunicator * getInstance(std::shared_ptr<IsoTpThreadState>)

What is causing this error and how can I fix it? The overloaded method is required for instance creation, the method without parameters is used for pure instance retrieval.

EDIT: As per request more code for the example.

#include <memory>
#include <stdint.h>
#include <linux/can.h>
#include <linux/can/raw.h>

using std::shared_ptr;

//================
// Class in question
//================

struct ThreadState {
    int32_t socketFd;
    uint32_t sendId;
};

class CanCommunicator {
    #define null NULL

    public: // +++ STATIC +++
        static CanCommunicator* getInstance(shared_ptr<ThreadState> state);
        static CanCommunicator* getInstance();
    public:
        shared_ptr<ThreadState> getThreadState() { return this->threadState; }
    protected:
        CanCommunicator(shared_ptr<ThreadState> state);
    private: // +++ STATIC +++
        static CanCommunicator* instance;
    private:
        shared_ptr<ThreadState> threadState;
};


/*
 +++++++++++++++++++++++++++++++++++++
 +++       STATIC VARIABLES        +++
 +++++++++++++++++++++++++++++++++++++
 */

CanCommunicator* CanCommunicator::instance = null;


/*
 +++++++++++++++++++++++++++++++++++++
 +++        STATIC METHODS         +++
 +++++++++++++++++++++++++++++++++++++
 */

CanCommunicator* CanCommunicator::getInstance(shared_ptr<ThreadState> state) {
    if (state == null && instance == null)
        throw "Cannot instantiate from nullptr!";

    return instance == null ? (instance = new CanCommunicator(state)) : instance;
}

CanCommunicator* CanCommunicator::getInstance() { return instance == null ? throw "No instance found!" : instance; }

CanCommunicator::CanCommunicator(shared_ptr<ThreadState> state) {
    this->threadState = state;        
}

//================
// Calling code
//================

int canSendData(int32_t skt, uint32_t sendCanId, const uint8_t* data, uint8_t dataLength, uint8_t extended) {
    struct can_frame myCanFrame;
    return (int)write(skt, &myCanFrame, sizeof(myCanFrame));
}

int isotp_user_send_can(const uint32_t arbitrationId, const uint8_t* data, const uint8_t size) {
    auto tState = CanCommunicator::getInstance()->getThreadState(); //<-------- Error originates here
    return canSendData(tState->socketFd, (int)tState->sendId, data, size, false) > 0 ? 0 : 1;
}

Answer 1

Thanks to Radoslaw's suggestion, I simply renamed the offending function to getInstanceByState().

This seems to be a bug in the version of GCC (4.4.5) I'm using, so there is no true fix but to wait until I can use a (much) newer compiler version.

Thank you to all who helped and gave suggestions.