The C++ language provides function overloading, which means that you can write many functions with the same name (providing each takes parameters of different types). All C++ function names are encoded into a low-level assembly label (this process is known as mangling). The c++filt program does the inverse mapping: it decodes (demangles) low-level names into user-level names so that the linker can keep these overloaded functions from clashing.

Every alphanumeric word (consisting of letters, digits, underscores, dollars, or periods) seen in the input is a potential label. If the label decodes into a C++ name, the C++ name replaces the low-level name in the output.

You can use c++filt to decipher individual symbols:

c++filt symbol

-_
--strip-underscores
On some systems, both the C and C++ compilers put an underscore in front of every name. For example, the C name, foo, gets the low-level name, _foo. This option removes the initial underscore. Whether c++filt removes the underscore by default is target dependent.
-n
--no-strip-underscores
Do not remove the initial underscore.
-s format
--format=format
GNU nm can decode three different methods of mangling, used by different C++ compilers. The argument to this option selects which method it uses:
• gnu

The one used by the GNU compiler (the default method).
 
• lucid

The one used by the Lucid compiler.
 
• arm

The one specified by the C++ Annotated Reference Manual.
--help
Print a summary of the options to c++filt and exit.
--version
Print the version number of c++filt and exit.
Warning:
c++filt is a new utility, and the details of its user interface are subject to change in future releases. In particular, a command-line option may be required in the future to decode a name passed as an argument on the command line; for example, c++filt symbol may in a future release become c++filt option symbol.