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291 lines
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4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>c++filt (GNU Binary Utilities)</title>
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<meta name="description" content="c++filt (GNU Binary Utilities)">
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<meta name="keywords" content="c++filt (GNU Binary Utilities)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Binutils-Index.html#Binutils-Index" rel="index" title="Binutils Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="index.html#Top" rel="up" title="Top">
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</head>
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<body lang="en">
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<a name="c_002b_002bfilt"></a>
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<div class="header">
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<p>
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Next: <a href="addr2line.html#addr2line" accesskey="n" rel="next">addr2line</a>, Previous: <a href="strip.html#strip" accesskey="p" rel="prev">strip</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Binutils-Index.html#Binutils-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="c_002b_002bfilt-1"></a>
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<h2 class="chapter">9 c++filt</h2>
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<a name="index-c_002b_002bfilt"></a>
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<a name="index-demangling-C_002b_002b-symbols"></a>
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<div class="smallexample">
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<pre class="smallexample">c++filt [<samp>-_</samp>|<samp>--strip-underscore</samp>]
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[<samp>-n</samp>|<samp>--no-strip-underscore</samp>]
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[<samp>-p</samp>|<samp>--no-params</samp>]
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[<samp>-t</samp>|<samp>--types</samp>]
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[<samp>-i</samp>|<samp>--no-verbose</samp>]
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[<samp>-r</samp>|<samp>--no-recurse-limit</samp>]
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[<samp>-R</samp>|<samp>--recurse-limit</samp>]
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[<samp>-s</samp> <var>format</var>|<samp>--format=</samp><var>format</var>]
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[<samp>--help</samp>] [<samp>--version</samp>] [<var>symbol</var>…]
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</pre></div>
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<a name="index-cxxfilt"></a>
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<p>The C++ and Java languages provide function overloading, which means
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that you can write many functions with the same name, providing that
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each function takes parameters of different types. In order to be
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able to distinguish these similarly named functions C++ and Java
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encode them into a low-level assembler name which uniquely identifies
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each different version. This process is known as <em>mangling</em>. The
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<code>c++filt</code>
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<a name="DOCF1" href="#FOOT1"><sup>1</sup></a>
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program does the inverse mapping: it decodes (<em>demangles</em>) low-level
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names into user-level names so that they can be read.
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</p>
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<p>Every alphanumeric word (consisting of letters, digits, underscores,
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dollars, or periods) seen in the input is a potential mangled name.
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If the name decodes into a C++ name, the C++ name replaces the
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low-level name in the output, otherwise the original word is output.
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In this way you can pass an entire assembler source file, containing
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mangled names, through <code>c++filt</code> and see the same source file
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containing demangled names.
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</p>
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<p>You can also use <code>c++filt</code> to decipher individual symbols by
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passing them on the command line:
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</p>
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<div class="example">
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<pre class="example">c++filt <var>symbol</var>
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</pre></div>
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<p>If no <var>symbol</var> arguments are given, <code>c++filt</code> reads symbol
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names from the standard input instead. All the results are printed on
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the standard output. The difference between reading names from the
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command line versus reading names from the standard input is that
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command-line arguments are expected to be just mangled names and no
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checking is performed to separate them from surrounding text. Thus
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for example:
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</p>
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<div class="smallexample">
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<pre class="smallexample">c++filt -n _Z1fv
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</pre></div>
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<p>will work and demangle the name to “f()” whereas:
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</p>
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<div class="smallexample">
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<pre class="smallexample">c++filt -n _Z1fv,
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</pre></div>
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<p>will not work. (Note the extra comma at the end of the mangled
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name which makes it invalid). This command however will work:
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</p>
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<div class="smallexample">
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<pre class="smallexample">echo _Z1fv, | c++filt -n
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</pre></div>
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<p>and will display “f(),”, i.e., the demangled name followed by a
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trailing comma. This behaviour is because when the names are read
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from the standard input it is expected that they might be part of an
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assembler source file where there might be extra, extraneous
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characters trailing after a mangled name. For example:
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</p>
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<div class="smallexample">
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<pre class="smallexample"> .type _Z1fv, @function
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</pre></div>
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<dl compact="compact">
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<dt><code>-_</code></dt>
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<dt><code>--strip-underscore</code></dt>
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<dd><p>On some systems, both the C and C++ compilers put an underscore in front
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of every name. For example, the C name <code>foo</code> gets the low-level
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name <code>_foo</code>. This option removes the initial underscore. Whether
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<code>c++filt</code> removes the underscore by default is target dependent.
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</p>
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</dd>
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<dt><code>-n</code></dt>
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<dt><code>--no-strip-underscore</code></dt>
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<dd><p>Do not remove the initial underscore.
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</p>
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</dd>
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<dt><code>-p</code></dt>
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<dt><code>--no-params</code></dt>
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<dd><p>When demangling the name of a function, do not display the types of
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the function’s parameters.
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</p>
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</dd>
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<dt><code>-t</code></dt>
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<dt><code>--types</code></dt>
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<dd><p>Attempt to demangle types as well as function names. This is disabled
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by default since mangled types are normally only used internally in
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the compiler, and they can be confused with non-mangled names. For example,
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a function called “a” treated as a mangled type name would be
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demangled to “signed char”.
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</p>
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</dd>
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<dt><code>-i</code></dt>
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<dt><code>--no-verbose</code></dt>
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<dd><p>Do not include implementation details (if any) in the demangled
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output.
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</p>
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</dd>
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<dt><code>-r</code></dt>
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<dt><code>-R</code></dt>
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<dt><code>--recurse-limit</code></dt>
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<dt><code>--no-recurse-limit</code></dt>
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<dt><code>--recursion-limit</code></dt>
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<dt><code>--no-recursion-limit</code></dt>
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<dd><p>Enables or disables a limit on the amount of recursion performed
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whilst demangling strings. Since the name mangling formats allow for
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an inifinite level of recursion it is possible to create strings whose
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decoding will exhaust the amount of stack space available on the host
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machine, triggering a memory fault. The limit tries to prevent this
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from happening by restricting recursion to 2048 levels of nesting.
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</p>
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<p>The default is for this limit to be enabled, but disabling it may be
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necessary in order to demangle truly complicated names. Note however
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that if the recursion limit is disabled then stack exhaustion is
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possible and any bug reports about such an event will be rejected.
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</p>
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<p>The <samp>-r</samp> option is a synonym for the
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<samp>--no-recurse-limit</samp> option. The <samp>-R</samp> option is a
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synonym for the <samp>--recurse-limit</samp> option.
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</p>
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</dd>
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<dt><code>-s <var>format</var></code></dt>
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<dt><code>--format=<var>format</var></code></dt>
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<dd><p><code>c++filt</code> can decode various methods of mangling, used by
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different compilers. The argument to this option selects which
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method it uses:
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</p>
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<dl compact="compact">
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<dt><code>auto</code></dt>
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<dd><p>Automatic selection based on executable (the default method)
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</p></dd>
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<dt><code>gnu</code></dt>
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<dd><p>the one used by the <small>GNU</small> C++ compiler (g++)
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</p></dd>
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<dt><code>lucid</code></dt>
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<dd><p>the one used by the Lucid compiler (lcc)
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</p></dd>
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<dt><code>arm</code></dt>
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<dd><p>the one specified by the C++ Annotated Reference Manual
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</p></dd>
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<dt><code>hp</code></dt>
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<dd><p>the one used by the HP compiler (aCC)
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</p></dd>
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<dt><code>edg</code></dt>
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<dd><p>the one used by the EDG compiler
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</p></dd>
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<dt><code>gnu-v3</code></dt>
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<dd><p>the one used by the <small>GNU</small> C++ compiler (g++) with the V3 ABI.
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</p></dd>
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<dt><code>java</code></dt>
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<dd><p>the one used by the <small>GNU</small> Java compiler (gcj)
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</p></dd>
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<dt><code>gnat</code></dt>
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<dd><p>the one used by the <small>GNU</small> Ada compiler (GNAT).
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</p></dd>
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</dl>
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</dd>
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<dt><code>--help</code></dt>
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<dd><p>Print a summary of the options to <code>c++filt</code> and exit.
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</p>
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</dd>
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<dt><code>--version</code></dt>
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<dd><p>Print the version number of <code>c++filt</code> and exit.
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</p></dd>
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</dl>
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<blockquote>
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<p><em>Warning:</em> <code>c++filt</code> is a new utility, and the details of its
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user interface are subject to change in future releases. In particular,
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a command-line option may be required in the future to decode a name
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passed as an argument on the command line; in other words,
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</p>
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<div class="example">
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<pre class="example">c++filt <var>symbol</var>
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</pre></div>
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<p>may in a future release become
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</p>
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<div class="example">
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<pre class="example">c++filt <var>option</var> <var>symbol</var>
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</pre></div>
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</blockquote>
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<div class="footnote">
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<hr>
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<h4 class="footnotes-heading">Footnotes</h4>
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<h3><a name="FOOT1" href="#DOCF1">(1)</a></h3>
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<p>MS-DOS does not allow <kbd>+</kbd> characters in file names, so on
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MS-DOS this program is named <code>CXXFILT</code>.</p>
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</div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="addr2line.html#addr2line" accesskey="n" rel="next">addr2line</a>, Previous: <a href="strip.html#strip" accesskey="p" rel="prev">strip</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Binutils-Index.html#Binutils-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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