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---
DIR commit c8661ffad4c2bbf1dd9138c4e8de7d86396cd070
DIR parent 140c21e2f1fee2016af107b87f42a591f300f56a
HTML Author: rsc <devnull@localhost>
Date: Tue, 29 Nov 2005 04:05:50 +0000
demangling docs
Diffstat:
A src/libmach/gpcompare.texi | 236 +++++++++++++++++++++++++++++++
A src/libmach/gxxint_15.html | 375 +++++++++++++++++++++++++++++++
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DIR diff --git a/src/libmach/gpcompare.texi b/src/libmach/gpcompare.texi
t@@ -0,0 +1,236 @@
+@node ANSI
+@chapter @sc{gnu} C++ Conformance to @sc{ansi} C++
+
+These changes in the @sc{gnu} C++ compiler were made to comply more
+closely with the @sc{ansi} base document, @cite{The Annotated C++
+Reference Manual} (the @sc{arm}). Further reducing the divergences from
+@sc{ansi} C++ is a continued goal of the @sc{gnu} C++ Renovation
+Project.
+
+@b{Section 3.4}, @i{Start and Termination}. It is now invalid to take
+the address of the function @samp{main()}.
+
+@b{Section 4.8}, @i{Pointers to Members}. The compiler produces
+an error for trying to convert between a pointer to a member and the type
+@samp{void *}.
+
+@b{Section 5.2.5}, @i{Increment and Decrement}. It is an error to use
+the increment and decrement operators on an enumerated type.
+
+@b{Section 5.3.2}, @i{Sizeof}. Doing @code{sizeof} on a function is now
+an error.
+
+@b{Section 5.3.4}, @i{Delete}. The syntax of a @i{cast-expression} is
+now more strictly controlled.
+
+@b{Section 7.1.1}, @i{Storage Class Specifiers}. Using the
+@code{static} and @code{extern} specifiers can now only be applied to
+names of objects, functions, and anonymous unions.
+
+@b{Section 7.1.1}, @i{Storage Class Specifiers}. The compiler no longer complains
+about taking the address of a variable which has been declared to have @code{register}
+storage.
+
+@b{Section 7.1.2}, @i{Function Specifiers}. The compiler produces an
+error when the @code{inline} or @code{virtual} specifiers are
+used on anything other than a function.
+
+@b{Section 8.3}, @i{Function Definitions}. It is now an error to shadow
+a parameter name with a local variable; in the past, the compiler only
+gave a warning in such a situation.
+
+@b{Section 8.4.1}, @i{Aggregates}. The rules concerning declaration of
+an aggregate are now all checked in the @sc{gnu} C++ compiler; they
+include having no private or protected members and no base classes.
+
+@b{Section 8.4.3}, @i{References}. Declaring an array of references is
+now forbidden. Initializing a reference with an initializer list is
+also considered an error.
+
+@b{Section 9.5}, @i{Unions}. Global anonymous unions must be declared
+@code{static}.
+
+@b{Section 11.4}, @i{Friends}. Declaring a member to be a friend of a
+type that has not yet been defined is an error.
+
+@b{Section 12.1}, @i{Constructors}. The compiler generates a
+default copy constructor for a class if no constructor has been declared.
+
+@ignore
+@b{Section 12.4}, @i{Destructors}. In accordance with the @sc{ansi} C++
+draft standard working paper, a pure virtual destructor must now be
+defined.
+@end ignore
+
+@b{Section 12.6.2}, @i{Special Member Functions}. When using a
+@i{mem-initializer} list, the compiler will now initialize class members
+in declaration order, not in the order in which you specify them.
+Also, the compiler enforces the rule that non-static @code{const}
+and reference members must be initialized with a @i{mem-initializer}
+list when their class does not have a constructor.
+
+@b{Section 12.8}, @i{Copying Class Objects}. The compiler generates
+default copy constructors correctly, and supplies default assignment
+operators compatible with user-defined ones.
+
+@b{Section 13.4}, @i{Overloaded Operators}. An overloaded operator may
+no longer have default arguments.
+
+@b{Section 13.4.4}, @i{Function Call}. An overloaded @samp{operator ()}
+must be a non-static member function.
+
+@b{Section 13.4.5}, @i{Subscripting}. An overloaded @samp{operator []}
+must be a non-static member function.
+
+@b{Section 13.4.6}, @i{Class Member Access}. An overloaded @samp{operator ->}
+must be a non-static member function.
+
+@b{Section 13.4.7}, @i{Increment and Decrement}. The compiler will now
+make sure a postfix @samp{@w{operator ++}} or @samp{@w{operator --}} has an
+@code{int} as its second argument.
+
+
+@node Encoding
+@chapter Name Encoding in @sc{gnu} C++
+
+@c FIXME!! rewrite name encoding section
+@c ...to give complete rules rather than diffs from ARM.
+@c To avoid plagiarism, invent some different way of structuring the
+@c description of the rules than what ARM uses.
+
+@cindex mangling
+@cindex name encoding
+@cindex encoding information in names
+In order to support its strong typing rules and the ability to provide
+function overloading, the C++ programming language @dfn{encodes}
+information about functions and objects, so that conflicts across object
+files can be detected during linking. @footnote{This encoding is also
+sometimes called, whimsically enough, @dfn{mangling}; the corresponding
+decoding is sometimes called @dfn{demangling}.} These rules tend to be
+unique to each individual implementation of C++.
+
+The scheme detailed in the commentary for 7.2.1 of @cite{The Annotated
+Reference Manual} offers a description of a possible implementation
+which happens to closely resemble the @code{cfront} compiler. The
+design used in @sc{gnu} C++ differs from this model in a number of ways:
+
+@itemize @bullet
+@item
+In addition to the basic types @code{void}, @code{char}, @code{short},
+@code{int}, @code{long}, @code{float}, @code{double}, and @code{long
+double}, @sc{gnu} C++ supports two additional types: @code{wchar_t}, the wide
+character type, and @code{long long} (if the host supports it). The
+encodings for these are @samp{w} and @samp{x} respectively.
+
+@item
+According to the @sc{arm}, qualified names (e.g., @samp{foo::bar::baz}) are
+encoded with a leading @samp{Q}. Followed by the number of
+qualifications (in this case, three) and the respective names, this
+might be encoded as @samp{Q33foo3bar3baz}. @sc{gnu} C++ adds a leading
+underscore to the list, producing @samp{_Q33foo3bar3baz}.
+
+@item
+The operator @samp{*=} is encoded as @samp{__aml}, not @samp{__amu}, to
+match the normal @samp{*} operator, which is encoded as @samp{__ml}.
+
+@c XXX left out ->(), __wr
+@item
+In addition to the normal operators, @sc{gnu} C++ also offers the minimum and
+maximum operators @samp{>?} and @samp{<?}, encoded as @samp{__mx} and
+@samp{__mn}, and the conditional operator @samp{?:}, encoded as @samp{__cn}.
+
+@cindex destructors, encoding of
+@cindex constructors, encoding of
+@item
+Constructors are encoded as simply @samp{__@var{name}}, where @var{name}
+is the encoded name (e.g., @code{3foo} for the @code{foo} class
+constructor). Destructors are encoded as two leading underscores
+separated by either a period or a dollar sign, depending on the
+capabilities of the local host, followed by the encoded name. For
+example, the destructor @samp{foo::~foo} is encoded as @samp{_$_3foo}.
+
+@item
+Virtual tables are encoded with a prefix of @samp{_vt}, rather than
+@samp{__vtbl}. The names of their classes are separated by dollar signs
+(or periods), and not encoded as normal: the virtual table for
+@code{foo} is @samp{__vt$foo}, and the table for @code{foo::bar} is
+named @samp{__vt$foo$bar}.
+
+@item
+Static members are encoded as a leading underscore, followed by the
+encoded name of the class in which they appear, a separating dollar sign
+or period, and finally the unencoded name of the variable. For example,
+if the class @code{foo} contains a static member @samp{bar}, its
+encoding would be @samp{_3foo$bar}.
+
+@item
+@sc{gnu} C++ is not as aggressive as other compilers when it comes to always
+generating @samp{Fv} for functions with no arguments. In particular,
+the compiler does not add the sequence to conversion operators. The
+function @samp{foo::bar()} is encoded as @samp{bar__3foo}, not
+@samp{bar__3fooFv}.
+
+@item
+The argument list for methods is not prefixed by a leading @samp{F}; it
+is considered implied.
+
+@item
+@sc{gnu} C++ approaches the task of saving space in encodings
+differently from that noted in the @sc{arm}. It does use the
+@samp{T@var{n}} and @samp{N@var{x}@var{y}} codes to signify copying the
+@var{n}th argument's type, and making the next @var{x} arguments be the
+type of the @var{y}th argument, respectively. However, the values for
+@var{n} and @var{y} begin at zero with @sc{gnu} C++, whereas the
+@sc{arm} describes them as starting at one. For the function @samp{foo
+(bartype, bartype)}, @sc{gnu} C++ uses @samp{foo__7bartypeT0}, while
+compilers following the @sc{arm} example generate @samp{foo__7bartypeT1}.
+
+@c Note it loses on `foo (int, int, int, int, int)'.
+@item
+@sc{gnu} C++ does not bother using the space-saving methods for types whose
+encoding is a single character (like an integer, encoded as @samp{i}).
+This is useful in the most common cases (two @code{int}s would result in
+using three letters, instead of just @samp{ii}).
+@end itemize
+
+@c @node Cfront
+@c @chapter @code{cfront} Compared to @sc{gnu} C++
+@c
+@c
+@c FIXME!! Fill in. Consider points in the following:
+@c
+@c @display
+@c Date: Thu, 2 Jan 92 21:35:20 EST
+@c From: raeburn@@cygnus.com
+@c Message-Id: <9201030235.AA10999@@cambridge.cygnus.com>
+@c To: mrs@@charlie.secs.csun.edu
+@c Cc: g++@@cygnus.com
+@c Subject: Re: ARM and GNU C++ incompatabilities
+@c
+@c Along with that, we should probably describe how g++ differs from
+@c cfront, in ways that the users will notice. (E.g., cfront supposedly
+@c allows "free (new char[10])"; does g++? How do the template
+@c implementations differ? "New" placement syntax?)
+@c @end display
+@c
+@c XXX For next revision.
+@c
+@c GNU C++:
+@c * supports expanding inline functions in many situations,
+@c including those which have static objects, use `for' statements,
+@c and other situations. Part of this versatility is due to is
+@c ability to not always generate temporaries for assignments.
+@c * deliberately allows divide by 0 and mod 0, since [according
+@c to Wilson] there are actually situations where you'd like to allow
+@c such things. Note on most systems it will cause some sort of trap
+@c or bus error. Cfront considers it an error.
+@c * does [appear to] support nested classes within templates.
+@c * conversion functions among baseclasses are all usable by
+@c a class that's derived from all of those bases.
+@c * sizeof works even when the class is defined within its ()'s
+@c * conditional expressions work with member fns and pointers to
+@c members.
+@c * can handle non-trivial declarations of variables within switch
+@c statements.
+@c
+@c Cfront:
DIR diff --git a/src/libmach/gxxint_15.html b/src/libmach/gxxint_15.html
t@@ -0,0 +1,375 @@
+<HTML>
+<HEAD>
+<!-- This HTML file has been created by texi2html 1.52
+ from gxxint.texi on 27 August 1999 -->
+
+<TITLE>G++ internals - Mangling</TITLE>
+</HEAD>
+<BODY>
+Go to the <A HREF="gxxint_1.html">first</A>, <A HREF="gxxint_14.html">previous</A>, <A HREF="gxxint_16.html">next</A>, <A HREF="gxxint_16.html">last</A> section, <A HREF="gxxint_toc.html">table of contents</A>.
+<P><HR><P>
+
+
+<H2><A NAME="SEC20" HREF="gxxint_toc.html#TOC20">Function name mangling for C++ and Java</A></H2>
+
+<P>
+Both C++ and Jave provide overloaded function and methods,
+which are methods with the same types but different parameter lists.
+Selecting the correct version is done at compile time.
+Though the overloaded functions have the same name in the source code,
+they need to be translated into different assembler-level names,
+since typical assemblers and linkers cannot handle overloading.
+This process of encoding the parameter types with the method name
+into a unique name is called <EM>name mangling</EM>. The inverse
+process is called <EM>demangling</EM>.
+
+</P>
+<P>
+It is convenient that C++ and Java use compatible mangling schemes,
+since the makes life easier for tools such as gdb, and it eases
+integration between C++ and Java.
+
+</P>
+<P>
+Note there is also a standard "Jave Native Interface" (JNI) which
+implements a different calling convention, and uses a different
+mangling scheme. The JNI is a rather abstract ABI so Java can call methods
+written in C or C++;
+we are concerned here about a lower-level interface primarily
+intended for methods written in Java, but that can also be used for C++
+(and less easily C).
+
+</P>
+
+
+<H3><A NAME="SEC21" HREF="gxxint_toc.html#TOC21">Method name mangling</A></H3>
+
+<P>
+C++ mangles a method by emitting the function name, followed by <CODE>__</CODE>,
+followed by encodings of any method qualifiers (such as <CODE>const</CODE>),
+followed by the mangling of the method's class,
+followed by the mangling of the parameters, in order.
+
+</P>
+<P>
+For example <CODE>Foo::bar(int, long) const</CODE> is mangled
+as <SAMP>`bar__C3Fooil'</SAMP>.
+
+</P>
+<P>
+For a constructor, the method name is left out.
+That is <CODE>Foo::Foo(int, long) const</CODE> is mangled
+as <SAMP>`__C3Fooil'</SAMP>.
+
+</P>
+<P>
+GNU Java does the same.
+
+</P>
+
+
+<H3><A NAME="SEC22" HREF="gxxint_toc.html#TOC22">Primitive types</A></H3>
+
+<P>
+The C++ types <CODE>int</CODE>, <CODE>long</CODE>, <CODE>short</CODE>, <CODE>char</CODE>,
+and <CODE>long long</CODE> are mangled as <SAMP>`i'</SAMP>, <SAMP>`l'</SAMP>,
+<SAMP>`s'</SAMP>, <SAMP>`c'</SAMP>, and <SAMP>`x'</SAMP>, respectively.
+The corresponding unsigned types have <SAMP>`U'</SAMP> prefixed
+to the mangling. The type <CODE>signed char</CODE> is mangled <SAMP>`Sc'</SAMP>.
+
+</P>
+<P>
+The C++ and Java floating-point types <CODE>float</CODE> and <CODE>double</CODE>
+are mangled as <SAMP>`f'</SAMP> and <SAMP>`d'</SAMP> respectively.
+
+</P>
+<P>
+The C++ <CODE>bool</CODE> type and the Java <CODE>boolean</CODE> type are
+mangled as <SAMP>`b'</SAMP>.
+
+</P>
+<P>
+The C++ <CODE>wchar_t</CODE> and the Java <CODE>char</CODE> types are
+mangled as <SAMP>`w'</SAMP>.
+
+</P>
+<P>
+The Java integral types <CODE>byte</CODE>, <CODE>short</CODE>, <CODE>int</CODE>
+and <CODE>long</CODE> are mangled as <SAMP>`c'</SAMP>, <SAMP>`s'</SAMP>, <SAMP>`i'</SAMP>,
+and <SAMP>`x'</SAMP>, respectively.
+
+</P>
+<P>
+C++ code that has included <CODE>javatypes.h</CODE> will mangle
+the typedefs <CODE>jbyte</CODE>, <CODE>jshort</CODE>, <CODE>jint</CODE>
+and <CODE>jlong</CODE> as respectively <SAMP>`c'</SAMP>, <SAMP>`s'</SAMP>, <SAMP>`i'</SAMP>,
+and <SAMP>`x'</SAMP>. (This has not been implemented yet.)
+
+</P>
+
+
+<H3><A NAME="SEC23" HREF="gxxint_toc.html#TOC23">Mangling of simple names</A></H3>
+
+<P>
+A simple class, package, template, or namespace name is
+encoded as the number of characters in the name, followed by
+the actual characters. Thus the class <CODE>Foo</CODE>
+is encoded as <SAMP>`3Foo'</SAMP>.
+
+</P>
+<P>
+If any of the characters in the name are not alphanumeric
+(i.e not one of the standard ASCII letters, digits, or '_'),
+or the initial character is a digit, then the name is
+mangled as a sequence of encoded Unicode letters.
+A Unicode encoding starts with a <SAMP>`U'</SAMP> to indicate
+that Unicode escapes are used, followed by the number of
+bytes used by the Unicode encoding, followed by the bytes
+representing the encoding. ASSCI letters and
+non-initial digits are encoded without change. However, all
+other characters (including underscore and initial digits) are
+translated into a sequence starting with an underscore,
+followed by the big-endian 4-hex-digit lower-case encoding of the character.
+
+</P>
+<P>
+If a method name contains Unicode-escaped characters, the
+entire mangled method name is followed by a <SAMP>`U'</SAMP>.
+
+</P>
+<P>
+For example, the method <CODE>X\u0319::M\u002B(int)</CODE> is encoded as
+<SAMP>`M_002b__U6X_0319iU'</SAMP>.
+
+</P>
+
+
+<H3><A NAME="SEC24" HREF="gxxint_toc.html#TOC24">Pointer and reference types</A></H3>
+
+<P>
+A C++ pointer type is mangled as <SAMP>`P'</SAMP> followed by the
+mangling of the type pointed to.
+
+</P>
+<P>
+A C++ reference type as mangled as <SAMP>`R'</SAMP> followed by the
+mangling of the type referenced.
+
+</P>
+<P>
+A Java object reference type is equivalent
+to a C++ pointer parameter, so we mangle such an parameter type
+as <SAMP>`P'</SAMP> followed by the mangling of the class name.
+
+</P>
+
+
+<H3><A NAME="SEC25" HREF="gxxint_toc.html#TOC25">Qualified names</A></H3>
+
+<P>
+Both C++ and Java allow a class to be lexically nested inside another
+class. C++ also supports namespaces (not yet implemented by G++).
+Java also supports packages.
+
+</P>
+<P>
+These are all mangled the same way: First the letter <SAMP>`Q'</SAMP>
+indicates that we are emitting a qualified name.
+That is followed by the number of parts in the qualified name.
+If that number is 9 or less, it is emitted with no delimiters.
+Otherwise, an underscore is written before and after the count.
+Then follows each part of the qualified name, as described above.
+
+</P>
+<P>
+For example <CODE>Foo::\u0319::Bar</CODE> is encoded as
+<SAMP>`Q33FooU5_03193Bar'</SAMP>.
+
+</P>
+
+
+<H3><A NAME="SEC26" HREF="gxxint_toc.html#TOC26">Templates</A></H3>
+
+<P>
+A class template instantiation is encoded as the letter <SAMP>`t'</SAMP>,
+followed by the encoding of the template name, followed
+the number of template parameters, followed by encoding of the template
+parameters. If a template parameter is a type, it is written
+as a <SAMP>`Z'</SAMP> followed by the encoding of the type.
+
+</P>
+<P>
+A function template specialization (either an instantiation or an
+explicit specialization) is encoded by an <SAMP>`H'</SAMP> followed by the
+encoding of the template parameters, as described above, followed by
+an <SAMP>`_'</SAMP>, the encoding of the argument types template function (not the
+specialization), another <SAMP>`_'</SAMP>, and the return type. (Like the
+argument types, the return type is the return type of the function
+template, not the specialization.) Template parameters in the argument
+and return types are encoded by an <SAMP>`X'</SAMP> for type parameters, or a
+<SAMP>`Y'</SAMP> for constant parameters, and an index indicating their position
+in the template parameter list declaration.
+
+</P>
+
+
+<H3><A NAME="SEC27" HREF="gxxint_toc.html#TOC27">Arrays</A></H3>
+
+<P>
+C++ array types are mangled by emitting <SAMP>`A'</SAMP>, followed by
+the length of the array, followed by an <SAMP>`_'</SAMP>, followed by
+the mangling of the element type. Of course, normally
+array parameter types decay into a pointer types, so you
+don't see this.
+
+</P>
+<P>
+Java arrays are objects. A Java type <CODE>T[]</CODE> is mangled
+as if it were the C++ type <CODE>JArray<T></CODE>.
+For example <CODE>java.lang.String[]</CODE> is encoded as
+<SAMP>`Pt6JArray1ZPQ34java4lang6String'</SAMP>.
+
+</P>
+
+
+<H3><A NAME="SEC28" HREF="gxxint_toc.html#TOC28">Table of demangling code characters</A></H3>
+
+<P>
+The following special characters are used in mangling:
+
+</P>
+<DL COMPACT>
+
+<DT><SAMP>`A'</SAMP>
+<DD>
+Indicates a C++ array type.
+
+<DT><SAMP>`b'</SAMP>
+<DD>
+Encodes the C++ <CODE>bool</CODE> type,
+and the Java <CODE>boolean</CODE> type.
+
+<DT><SAMP>`c'</SAMP>
+<DD>
+Encodes the C++ <CODE>char</CODE> type, and the Java <CODE>byte</CODE> type.
+
+<DT><SAMP>`C'</SAMP>
+<DD>
+A modifier to indicate a <CODE>const</CODE> type.
+Also used to indicate a <CODE>const</CODE> member function
+(in which cases it precedes the encoding of the method's class).
+
+<DT><SAMP>`d'</SAMP>
+<DD>
+Encodes the C++ and Java <CODE>double</CODE> types.
+
+<DT><SAMP>`e'</SAMP>
+<DD>
+Indicates extra unknown arguments <CODE>...</CODE>.
+
+<DT><SAMP>`f'</SAMP>
+<DD>
+Encodes the C++ and Java <CODE>float</CODE> types.
+
+<DT><SAMP>`F'</SAMP>
+<DD>
+Used to indicate a function type.
+
+<DT><SAMP>`H'</SAMP>
+<DD>
+Used to indicate a template function.
+
+<DT><SAMP>`i'</SAMP>
+<DD>
+Encodes the C++ and Java <CODE>int</CODE> types.
+
+<DT><SAMP>`J'</SAMP>
+<DD>
+Indicates a complex type.
+
+<DT><SAMP>`l'</SAMP>
+<DD>
+Encodes the C++ <CODE>long</CODE> type.
+
+<DT><SAMP>`P'</SAMP>
+<DD>
+Indicates a pointer type. Followed by the type pointed to.
+
+<DT><SAMP>`Q'</SAMP>
+<DD>
+Used to mangle qualified names, which arise from nested classes.
+Should also be used for namespaces (?).
+In Java used to mangle package-qualified names, and inner classes.
+
+<DT><SAMP>`r'</SAMP>
+<DD>
+Encodes the GNU C++ <CODE>long double</CODE> type.
+
+<DT><SAMP>`R'</SAMP>
+<DD>
+Indicates a reference type. Followed by the referenced type.
+
+<DT><SAMP>`s'</SAMP>
+<DD>
+Encodes the C++ and java <CODE>short</CODE> types.
+
+<DT><SAMP>`S'</SAMP>
+<DD>
+A modifier that indicates that the following integer type is signed.
+Only used with <CODE>char</CODE>.
+
+Also used as a modifier to indicate a static member function.
+
+<DT><SAMP>`t'</SAMP>
+<DD>
+Indicates a template instantiation.
+
+<DT><SAMP>`T'</SAMP>
+<DD>
+A back reference to a previously seen type.
+
+<DT><SAMP>`U'</SAMP>
+<DD>
+A modifier that indicates that the following integer type is unsigned.
+Also used to indicate that the following class or namespace name
+is encoded using Unicode-mangling.
+
+<DT><SAMP>`v'</SAMP>
+<DD>
+Encodes the C++ and Java <CODE>void</CODE> types.
+
+<DT><SAMP>`V'</SAMP>
+<DD>
+A modified for a <CODE>const</CODE> type or method.
+
+<DT><SAMP>`w'</SAMP>
+<DD>
+Encodes the C++ <CODE>wchar_t</CODE> type, and the Java <CODE>char</CODE> types.
+
+<DT><SAMP>`x'</SAMP>
+<DD>
+Encodes the GNU C++ <CODE>long long</CODE> type, and the Java <CODE>long</CODE> type.
+
+<DT><SAMP>`X'</SAMP>
+<DD>
+Encodes a template type parameter, when part of a function type.
+
+<DT><SAMP>`Y'</SAMP>
+<DD>
+Encodes a template constant parameter, when part of a function type.
+
+<DT><SAMP>`Z'</SAMP>
+<DD>
+Used for template type parameters.
+
+</DL>
+
+<P>
+The letters <SAMP>`G'</SAMP>, <SAMP>`M'</SAMP>, <SAMP>`O'</SAMP>, and <SAMP>`p'</SAMP>
+also seem to be used for obscure purposes ...
+
+</P>
+<P><HR><P>
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