Mangling

Mangling is a term used to describe processes that modify data to something else, often to encode metadata or guarantee uniqueness. In programming, name mangling refers to encoding a symbol's full declaration into its linker-visible name. This allows features such as function overloading, namespaces, and template instantiation to be implemented in languages that commit to a single symbol space.

In C++ and some other languages, the compiler generates mangled symbol names for functions, variables, and types; the exact encoding is compiler- and ABI-dependent. It lets two functions with the same name but different parameters coexist, and it preserves type information across translation units. An example would be mangled names that include the function name, parameter types, and template arguments. To refer back to a human-readable form, demangling is used, such as with the c++filt tool on Unix-like systems or the undname utility on Windows.

Some languages avoid or minimize mangling. C uses straightforward symbol names, while C++ and Rust use more complex schemes. Microsoft Visual C++ uses its own mangling scheme; invoking extern "C" on a function disables name mangling to enable C linkage.

Impact and compatibility are practical considerations. Linkers must apply the same mangling scheme across object files; mismatches cause linker errors. The scheme is part of the ABI, and changes across compiler versions can break compatibility. Related terms include demangling, ABI, and the broader concept of name decoration in language runtimes.