How can I demangle std::type_info::name to reveal the underlying type in C ?

De-Mangler for std::type_info::name: Unveiling the Demystified Name

The name mangled by std::type_info remains enigmatic, rendering it challenging to comprehend the underlying type. The quest for a solution that demangles this enigma has led to the exploration of various approaches.

Demangling the Mangled Name

One solution leverages C 11's powerful features and g 's libstdc library through the abi::__cxa_demangle function. This function decodes the mangled name, returning a human-readable string.

C 11 Implementation

In the C 11 implementation, the demangle function is included in the "type.hpp" header file, and the actual demangling logic resides in "type.cpp." The following code snippet illustrates:

#include "type.hpp"

std::string demangle(const char* name) {

    int status = -4; 
    std::unique_ptr<char, void(*)(void*)> res {
        abi::__cxa_demangle(name, NULL, NULL, &status),
        std::free
    };

    return (status==0) ? res.get() : name ;
}

C 98 Compatible Version

For those not utilizing C 11, an alternative remains available. The C 98 compatible implementation in "type.cpp" employs a different technique to demangle the name:

#include "type.hpp"

struct handle {
    char* p;
    handle(char* ptr) : p(ptr) { }
    ~handle() { std::free(p); }
};

std::string demangle(const char* name) {

    int status = -4; 
    handle result( abi::__cxa_demangle(name, NULL, NULL, &status) );

    return (status==0) ? result.p : name ;
}

Usage and Considerations

The demangled name can be retrieved using the type function, which accepts a reference to the type to be demangled. The following code demonstrates its usage:

#include "type.hpp"
struct Base { virtual ~Base() {} };
struct Derived : public Base { };

int main() {
    Base* ptr_base = new Derived();
    std::cout << "Type of ptr_base: " << type(ptr_base) << std::endl;
    std::cout << "Type of pointee: " << type(*ptr_base) << std::endl;
    delete ptr_base;
}

Conclusion

With these techniques, developers can now unveil the hidden identities of mangled type names, gaining a clearer understanding of the types involved in their code.

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