Why this function variable only works if it's static? - c++

Question

I'm trying to put a bunch of sounds in a std::vector because it's very convenient.
I'm using an auxiliary variable called laser, load the sound into it and, if it's everything ok, push_back into the vector.
When I try to play any the sound, nothing happens, not even error messages which should be printed if anything goes wrong.
Just for curiosity I made laser static and voilá, it works flawlessly (or it seems to).
I'd like to know why.
Header file:
// audio_system.h
#ifndef KUGE_HEADERS_AUDIO_SYSTEM_H_
#define KUGE_HEADERS_AUDIO_SYSTEM_H_
#include "event.h"
#include "system.h"
#include "../sdl2_wrappers/sdl2_wrappers.h"
#include "../include/resources_path.h"
#include <vector>
namespace kuge {
class AudioSystem : virtual public System {
public:
AudioSystem(EventBus& bus): System(bus) {}
void handleEvent(const Event& event);
static bool loadResources();
private:
static void generateRandomSequence();
static std::vector<ktp::SDL2_Sound> lasers_;
};
} // end namespace kuge
#endif // KUGE_HEADERS_AUDIO_SYSTEM_H_
cpp file:
#include "event_bus.h"
#include "audio_system.h"
std::vector<ktp::SDL2_Sound> kuge::AudioSystem::lasers_{};
void kuge::AudioSystem::generateRandomSequence() {}
void kuge::AudioSystem::handleEvent(const Event& event) {
switch (event.getType()) {
case EventTypes::LaserFired:
if (lasers_[0].play() == -1) {
ktp::logSDLError("laser_.play");
}
break;
default:
break;
}
}
bool kuge::AudioSystem::loadResources() {
static ktp::SDL2_Sound laser{}; // here! If I don't make this static, nothing happens
if (!laser.loadSound(ktp::getResourcesPath() + "sounds/laser2.wav")) {
return false;
} else {
lasers_.push_back(laser);
}
ktp::logMessage("AudioSystem: resources loaded.");
return true;
}

Answer 1

OK, so following the advices from the comments, I've made the following changes to make ktp::SDL2_Sound class follow the rule of 0 and now it works without the need to set the laser variable to static. This solves the problem, but I'm still not sure why it worked being static.
class SDL2_Sound {
public:
//~SDL2_Sound() { free(); } // now I don't need any destructor
bool loadSound(const std::string& path);
int play(int loops = 0);
private:
void free();
// Mix_Chunk* sound_ = nullptr; // old raw pointer
std::shared_ptr<Mix_Chunk> sound_{};
};
/* void ktp::SDL2_Sound::free() {
if (sound_ != nullptr) {
Mix_FreeChunk(sound_);
sound_ = nullptr;
}
} */
bool ktp::SDL2_Sound::loadSound(const std::string& path) {
//free();
sound_.reset(Mix_LoadWAV(path.c_str()), &Mix_FreeChunk);
//sound_ = Mix_LoadWAV(path.c_str());
if (sound_ == nullptr) {
ktp::logSDLError("Mix_LoadWAV", path);
return false;
}
return true;
}