C++FILT(1) binutils-2.35.2 C++FILT(1)
GNU Development Tools GNU Development Tools
2021-01-30
NAME
c++filt - demangle C++ and Java symbols
SYNOPSIS
c++filt [-_|--strip-underscore]
[-n|--no-strip-underscore]
[-p|--no-params]
[-t|--types]
[-i|--no-verbose]
[-r|--no-recurse-limit]
[-R|--recurse-limit]
[-s format|--format=format]
[--help] [--version] [symbol...]
DESCRIPTION
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,
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C++FILT(1) binutils-2.35.2 C++FILT(1)
GNU Development Tools GNU Development Tools
2021-01-30
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
OPTIONS
-_
--strip-underscore
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-underscore
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.
-r
-R
--recurse-limit
--no-recurse-limit
--recursion-limit
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C++FILT(1) binutils-2.35.2 C++FILT(1)
GNU Development Tools GNU Development Tools
2021-01-30
--no-recursion-limit
Enables or disables a limit on the amount of recursion performed
whilst demangling strings. Since the name mangling formats allow
for an inifinite level of recursion it is possible to create
strings whose decoding will exhaust the amount of stack space
available on the host machine, triggering a memory fault. The
limit tries to prevent this from happening by restricting
recursion to 2048 levels of nesting.
The default is for this limit to be enabled, but disabling it may
be necessary in order to demangle truly complicated names. Note
however that if the recursion limit is disabled then stack
exhaustion is possible and any bug reports about such an event
will be rejected.
The -r option is a synonym for the --no-recurse-limit option. The
-R option is a synonym for the --recurse-limit option.
-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"
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C++FILT(1) binutils-2.35.2 C++FILT(1)
GNU Development Tools GNU Development Tools
2021-01-30
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.
@file
Read command-line options from file. The options read are
inserted in place of the original @file option. If file does not
exist, or cannot be read, then the option will be treated
literally, and not removed.
Options in file are separated by whitespace. A whitespace
character may be included in an option by surrounding the entire
option in either single or double quotes. Any character
(including a backslash) may be included by prefixing the character
to be included with a backslash. The file may itself contain
additional @file options; any such options will be processed
recursively.
FOOTNOTES
1. MS-DOS does not allow "+" characters in file names, so on MS-DOS
this program is named CXXFILT.
SEE ALSO
the Info entries for binutils.
COPYRIGHT
Copyright (c) 1991-2020 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".
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