I am creating a mathematical data structure in c++20 (Mingw-w64 clion) which i can partially offload from memory to storage and vice versa, Due to its capacity and size. While learning how i could work with memory i tested a particular code which to my knowledge it should work. But the app crashes due to segmentation violation (SIGSEGV) and i could not deduce why so. I would really appreciate your help.
//Utility
template<typename C, typename T>
std::basic_ostream<C, T> &
operator<<(std::basic_ostream<C, T> &_out, const logics::atomic_logic &_s) {
_out << _s.to_string();
return _out;
}
int main() {
using namespace std;
using namespace logics;
auto *pointer = (logic_sym *) malloc(sizeof(logic_sym));
*pointer = logic_sym(26);
std::cout << (*pointer) << std::endl;
free(pointer);
return 0;
}
yet the others below are working.
this one:-
int test2() {
using namespace std;
using namespace logics;
auto *pointer = (logic_sym *) malloc(sizeof(logic_sym));
*pointer = logic_sym(26);
string s=pointer->to_string();
std::cout << s<< std::endl;
free(pointer);
return 0;
}
and this:-
int test3() {
using namespace std;
using namespace logics;
auto *pointer = new logic_sym(26u);
*pointer = logic_sym(26u);
std::cout << *pointer << std::endl;
free(pointer);
return 0;
}
EDIT
The atomic_logic is not quite important but below is the logic_sym.
struct logic_sym final : public atomic_logic {
[[nodiscard]] constexpr bool cached() const override {
return false;
};
[[nodiscard]] const logic_id &get_id() const override {
return id;
}
[[nodiscard]] constexpr logic_type get_type() const override {
return logic_type::sym_t;
}
constexpr int operator<=>(const logic_id &_id) const override {
return id - _id;
}
[[nodiscard]] std::string to_string() const override {
if (id > 26)
return (std::string("p") + std::to_string(id));
return (std::string() + ((char) (id + 'a' - 1)));
}
[[maybe_unused]] explicit logic_sym(const logic_id &id) {
std::cout << "Aha! creating: " << id << std::endl;
this->id = id;
}
logic_sym(const logic_sym &orig)=delete;
private:
logic_id id;
};
You may not simply cast a void *
pointer to a pointer to logic_sym
. You must use a placement new operator to initialize the memory.
new(pointer) logic_sym(26)
However, why are you fussing with malloc
and free
instead of just using new
and delete
?`