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## 9 c++filt

         c++filt [-_|--strip-underscores]
                 [-n|--no-strip-underscores]
                 [-p|--no-params]
                 [-t|--types]
                 [-i|--no-verbose]
                 [-s format|--format=format]
                 [--help]  [--version]  [symbol...]

The C++ and Java languages provide function overloading, which means that you can write many functions with the same name, providing that each function takes parameters of different types. In order to be able to distinguish these similarly named functions C++ and Java encode them into a low-level assembler name which uniquely identifies each different version. This process is known as mangling. The c++filt 1 program does the inverse mapping: it decodes (demangles) low-level names into user-level names so that they can be read.

Every alphanumeric word (consisting of letters, digits, underscores, dollars, or periods) seen in the input is a potential mangled name. If the name decodes into a C++ name, the C++ name replaces the low-level name in the output, otherwise the original word is output. In this way you can pass an entire assembler source file, containing mangled names, through c++filt and see the same source file containing demangled names.

You can also use c++filt to decipher individual symbols by passing them on the command line:

         c++filt symbol

If no symbol arguments are given, c++filt reads symbol names from the standard input instead. All the results are printed on the standard output. The difference between reading names from the command line versus reading names from the standard input is that command line arguments are expected to be just mangled names and no checking is performed to separate them from surrounding text. Thus for example:

         c++filt -n _Z1fv

will work and demangle the name to “f()” whereas:

         c++filt -n _Z1fv,

will not work. (Note the extra comma at the end of the mangled name which makes it invalid). This command however will work:

         echo _Z1fv, | c++filt -n

and will display “f(),”, i.e., the demangled name followed by a trailing comma. This behaviour is because when the names are read from the standard input it is expected that they might be part of an assembler source file where there might be extra, extraneous characters trailing after a mangled name. For example:

             .type   _Z1fv, @function

-_
--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.
-j
--java
  Prints demangled names using Java syntax. The default is to use C++ syntax.
-n
--no-strip-underscores
  Do not remove the initial underscore.
-p
--no-params
  When demangling the name of a function, do not display the types of the function's parameters.
-t
--types
  Attempt to demangle types as well as function names. This is disabled by default since mangled types are normally only used internally in the compiler, and they can be confused with non-mangled names. For example, a function called “a” treated as a mangled type name would be demangled to “signed char”.
-i
--no-verbose
  Do not include implementation details (if any) in the demangled output.
-s format
--format=format
  c++filt can decode various methods of mangling, used by different compilers. The argument to this option selects which method it uses:
  `auto`
    Automatic selection based on executable (the default method)
  `gnu`
    the one used by the gnu C++ compiler (g++)
  `lucid`
    the one used by the Lucid compiler (lcc)
  `arm`
    the one specified by the C++ Annotated Reference Manual
  `hp`
    the one used by the HP compiler (aCC)
  `edg`
    the one used by the EDG compiler
  `gnu-v3`
    the one used by the gnu C++ compiler (g++) with the V3 ABI.
  `java`
    the one used by the gnu Java compiler (gcj)
  `gnat`
    the one used by the gnu Ada compiler (GNAT).
--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; in other words,

>               c++filt symbol

> may in a future release become

>               c++filt option symbol

#### Footnotes

[1] MS-DOS does not allow `+` characters in file names, so on MS-DOS this program is named CXXFILT.