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Interpreting C++ Demangled Names

C++ Demangled Names

Some SAS/C components, such as the COOL pre-linker and the SAS/C Debugger, need to refer to overloadable names in their messages and reports, as in COOL diagnostic messages or debugger prompts to select one of several overloaded functions. In these contexts, a routine called the demangler is called to generate a demangled name, which is an approximation to the original C++ declaration of the name. For instance, the demangled form of reciprocal_ _Fd is reciprocal(double). The demangled name may fail to match the actual declaration of an object for any of several reasons:

The mangled name may not contain enough information to completely reproduce the original form. For instance, if a type is defined using a typedef, the typedef name is not present in the mangled name. For example:
```
typedef container box;
bool open(box *);
```
The demangled form of this open function will be open(container *).
In some cases, a demangled name may not even be valid C++. This can happen when valid C++ code requires the use of a typedef. For example:
```
typedef void (*functionp)(int);
class example {
   operator functionp(); /* convert example to functionp */
}
```
The demangled name for example::operator functionp above will be example::operator void(*)(int)() , which is not an acceptable syntax for a conversion operator.
In many contexts where mangled names are used, a limited amount of space is available to display the name. Not only are many C++ names long in their original form, but the expansion of typedefs can result in very long names for functions whose declarations are quite short. For instance, the complete demangled name of an extraction operator in the standard template library is as follows:
```
std::basic_ostream<char,std::char_traits<char> >::operator <<
      (std::basic_ostream<char,std::char_traits<char> >&(*)
      (std::basic_ostream<char,std::char_traits<char> >&))
```

Names such as that above generally must be compressed in some fashion in order to fit in a fixed-size field. Such compression loses information, and also produces a name that is not valid for C++. For example, the name above, in a COOL cross-reference, will possibly be compacted to the following:

std::basic_stream<char,std::char_traits<char> >::operator <<(...1)

Of course, this is not a valid C++ operator specification, and all information about the type of the argument has been lost. The combination of these factors can make demangled names quite difficult to interpret.

Note: See the information the information on the endisplaylimit COOL option in SAS/C Compiler and Library User's Guide for information about generating non-compacted names. [cautionend]

The remainder of this section describes the special conventions used in demangled names as an aid to figuring out the specific identifier a demangled name refers to.

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