c++ - How does returning values from a function work? -

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i had serious bug, forgot return value in function. problem though nothing returned worked fine under linux/windows , crashed under mac. discovered bug when turned on compiler warnings.

so here simple example:

#include <iostream>  class a{ public:     a(int p1, int p2, int p3): v1(p1), v2(p2), v3(p3)     {     }      int v1;     int v2;     int v3; };  a* geta(){     a* p = new a(1,2,3); //  return p; }  int main(){      a* = geta();      std::cerr << "a: v1=" << a->v1 << " v2=" << a->v2 << " v3=" << a->v3 << std::endl;        return 0; }

my question how can work under linux/windows without crashing? how returning of values done on lower level?

on intel architecture, simple values (integers , pointers) returned in eax register. register (among others) used temporary storage when moving values in memory , operand during calculations. whatever value left in register treated return value, , in case turned out wanted returned.


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