Why Does GCC\'s `typeid.name()` Return Mangled Names Instead of Plain Type Names?

GCC's Mangled Type Names: Demystifying the 'typeid.name()' Conundrum

When utilizing the 'typeid.name()' function with GCC, users may be surprised by the peculiar strings it returns. Unlike other compilers that provide unmangled class or struct names, GCC outputs a decorated name full of potential bafflement.

Delving into the Problem

Consider the following C code:

#include <iostream>
#include <typeinfo>

using namespace std;

struct Blah {};

int main() {
  cout << typeid(Blah).name() << endl;
  return 0;
}

Compiling this code with GCC 4.4.4 yields the perplexing result:

4Blah

In contrast, Visual C 2008 would have returned:

struct Blah

Unveiling the Mystery

The reason for this discrepancy lies in the implementation-defined nature of 'typeid.name()'. An implementation may elect to return dissimilar strings for distinct types or even identical strings for different types.

GCC's Decorated Names

GCC, by design, returns a decorated name for type information. This decorated name is a complex string that encompasses various details about the type, including its name and associated template arguments.

Demangling the Decorated Name

To make sense of GCC's decorated names, one can employ the 'c filt' command or the '__cxa_demangle' function. These tools enable the demangling of decorated names, revealing the underlying unmangled class or struct name.

Conclusion

While the behavior of 'typeid.name()' may vary across compilers, it is crucial to recognize the implementation-defined nature of its return. In the case of GCC, it returns decorated names, which require specialized tools to demangle for readability.

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