dump - Segmentation Fault C++, after parentheses operator -

i have class override parentheses operator. following code works:

int main(){      ..      a;      cout << a({0.5});      .. } 

while following code doesn't work

a fun(){      ..      a;      return a;      .. } int main(){      ..      a = fun();      cout << a({0.5}); } 

when execute second code, have following error:

segmentation fault (core dumped) 

i can't understand why.

edit:

this overriding of operator:

virtual arma::vec operator()(const inputc& input) override {     const arma::vec& x = params.normalizationf->normalize(base::phi(input));     forwardcomputation(x);     return params.normalizationo->restore(h.back()); } 

this constructor:

ffneuralnetwork_(features_<inputc, denseoutput>& phi, unsigned int neurons,                  unsigned int outputs) :     parametricregressor(phi, outputs), batchregressor_<inputc, arma::vec, denseoutput>(phi, outputs) {     layerfunction.push_back(new sigmoid());     layerfunction.push_back(new linear());      layerneurons.push_back(neurons);     layerneurons.push_back(outputs);      setupnetwork(); } 

and actually:

 typedef ffneuralnetwork_<arma::vec> ffneuralnetwork; 

where ffneuralnetwork class used in example.

here actual working code:

basisfunctions basisplane_ = identitybasis::generate(1); densefeatures phiplane_(basisplane_); ffneuralnetwork planenet(phiplane_, 10, 1); cout << planenet({0.5}); 

here not working code:

ffneuralnetwork createnetwork(..){     basisfunctions basisplane_ = identitybasis::generate(1);     densefeatures phiplane_(basisplane_);      ffneuralnetwork planenet(phiplane_, 10, 1);     return planenet; } .. ffneuralnetwork net = createnetwork(..); cout << net({0.5}); 

in bit of code you're passing local variable phiplane_ reference:

ffneuralnetwork createnetwork(..){     basisfunctions basisplane_ = identitybasis::generate(1);     densefeatures phiplane_(basisplane_);      ffneuralnetwork planenet(phiplane_, 10, 1); // <- here     return planenet; }  ffneuralnetwork net = createnetwork(..); cout << net({0.5}); 

once function returns object passed reference no longer exists no code should access after that. may or may not ok depending on happens in parametricregressor(phi, outputs), seems bit dubious me , explain problem.