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-_dnl__ Copyright (c) 1988 1989 1990 1991 Free Software Foundation, Inc.
-_dnl__ This file is part of the source for the GDB manual.
-@c M4 FRAGMENT: $Id$
-@node Data, Symbols, Source, Top
-@chapter Examining Data
-
-@cindex printing data
-@cindex examining data
-@kindex print
-@kindex inspect
-@c "inspect" isn't quite a synonym if you're using Epoch, which we don't
-@c document because it's nonstandard...  Under Epoch it displays in a
-@c different window or something like that.
-The usual way to examine data in your program is with the @code{print}
-command (abbreviated @code{p}), or its synonym @code{inspect}.  It
-evaluates and prints the value of any valid expression of the language
-the program is written in (for now, C or C++).  You type
-
-@example
-print @var{exp}
-@end example
-
-@noindent
-where @var{exp} is any valid expression (in the source language), and
-the value of @var{exp} is printed in a format appropriate to its data
-type.
-
-A more low-level way of examining data is with the @code{x} command.
-It examines data in memory at a specified address and prints it in a
-specified format.  @xref{Memory}.
-
-@menu
-* Expressions::			Expressions
-* Variables::			Program Variables
-* Arrays::			Artificial Arrays
-* Output formats::		Output formats
-* Memory::			Examining Memory
-* Auto Display::		Automatic Display
-* Print Settings::		Print Settings
-* Value History::		Value History
-* Convenience Vars::		Convenience Variables
-* Registers::			Registers
-* Floating Point Hardware::	Floating Point Hardware
-@end menu
-
-@node Expressions, Variables, Data, Data
-@section Expressions
-
-@cindex expressions
-@code{print} and many other _GDBN__ commands accept an expression and
-compute its value.  Any kind of constant, variable or operator defined
-by the programming language you are using is legal in an expression in
-_GDBN__.  This includes conditional expressions, function calls, casts
-and string constants.  It unfortunately does not include symbols defined
-by preprocessor @code{#define} commands, or C++ expressions involving
-@samp{::}, the name resolution operator.
-@c FIXME: actually C++ a::b works except in obscure circumstances where it
-@c FIXME...can conflict with GDB's own name scope resolution.
-
-Casts are supported in all languages, not just in C, because it is so
-useful to cast a number into a pointer so as to examine a structure
-at that address in memory.
-
-_GDBN__ supports three kinds of operator in addition to those of programming
-languages:
-
-@table @code
-@item @@
-@samp{@@} is a binary operator for treating parts of memory as arrays.
-@xref{Arrays}, for more information.
-
-@item ::
-@samp{::} allows you to specify a variable in terms of the file or
-function where it is defined.  @xref{Variables}.
-
-@item @{@var{type}@} @var{addr}
-Refers to an object of type @var{type} stored at address @var{addr} in
-memory.  @var{addr} may be any expression whose value is an integer or
-pointer (but parentheses are required around binary operators, just as in
-a cast).  This construct is allowed regardless of what kind of data is
-normally supposed to reside at @var{addr}.@refill
-@end table
-
-@node Variables, Arrays, Expressions, Data
-@section Program Variables
-
-The most common kind of expression to use is the name of a variable
-in your program.
-
-Variables in expressions are understood in the selected stack frame
-(@pxref{Selection}); they must either be global (or static) or be visible
-according to the scope rules of the programming language from the point of
-execution in that frame.  This means that in the function
-
-@example
-foo (a)
-     int a;
-@{
-  bar (a);
-  @{
-    int b = test ();
-    bar (b);
-  @}
-@}
-@end example
-
-@noindent
-the variable @code{a} is usable whenever the program is executing
-within the function @code{foo}, but the variable @code{b} is visible
-only while the program is executing inside the block in which @code{b}
-is declared.
-
-@cindex variable name conflict
-There is an exception: you can refer to a variable or function whose
-scope is a single source file even if the current execution point is not
-in this file.  But it is possible to have more than one such variable or
-function with the same name (in different source files).  If that happens,
-referring to that name has unpredictable effects.  If you wish, you can
-specify a variable in a particular file, using the colon-colon notation:
-
-@cindex colon-colon
-@kindex ::
-@example
-@var{file}::@var{variable}
-@end example
-
-@noindent
-Here @var{file} is the name of the source file whose variable you want.
-
-@cindex C++ name resolution
-This use of @samp{::} is very rarely in conflict with the very similar
-use of the same notation in C++.  _GDBN__ also supports use of the C++
-name resolution operator in _GDBN__ expressions.
-
-@node Arrays, Output formats, Variables, Data
-@section Artificial Arrays
-
-@cindex artificial array
-@kindex @@
-It is often useful to print out several successive objects of the
-same type in memory; a section of an array, or an array of
-dynamically determined size for which only a pointer exists in the
-program.
-
-This can be done by constructing an @dfn{artificial array} with the
-binary operator @samp{@@}.  The left operand of @samp{@@} should be
-the first element of the desired array, as an individual object.
-The right operand should be the desired length of the array.  The result is
-an array value whose elements are all of the type of the left argument.
-The first element is actually the left argument; the second element
-comes from bytes of memory immediately following those that hold the
-first element, and so on.  Here is an example.  If a program says
-
-@example
-int *array = (int *) malloc (len * sizeof (int));
-@end example
-
-@noindent
-you can print the contents of @code{array} with
-
-@example
-p *array@@len
-@end example
-
-The left operand of @samp{@@} must reside in memory.  Array values made
-with @samp{@@} in this way behave just like other arrays in terms of
-subscripting, and are coerced to pointers when used in expressions.
-Artificial arrays most often appear in expressions via the value history
-(@pxref{Value History}), after printing one out.)
-
-@node Output formats, Memory, Arrays, Data
-@section Output formats
-
-@cindex formatted output
-@cindex output formats
-By default, _GDBN__ prints a value according to its data type.  Sometimes
-this is not what you want.  For example, you might want to print a number
-in hex, or a pointer in decimal.  Or you might want to view data in memory
-at a certain address as a character string or as an instruction.  To do
-these things, specify an @dfn{output format} when you print a value.
-
-The simplest use of output formats is to say how to print a value
-already computed.  This is done by starting the arguments of the
-@code{print} command with a slash and a format letter.  The format
-letters supported are:
-
-@table @code
-@item x
-Regard the bits of the value as an integer, and print the integer in
-hexadecimal.
-
-@item d
-Print as integer in signed decimal.
-
-@item u
-Print as integer in unsigned decimal.
-
-@item o
-Print as integer in octal.
-
-@item t
-Print as integer in binary.  The letter @samp{t} stands for ``two''.
-
-@item a
-Print as an address, both absolute in hex and as an offset from the
-nearest preceding symbol.  This format can be used to discover where (in
-what function) an unknown address is located:
-@example
-(_GDBP__) p/a 0x54320
-_0__$3 = 0x54320 <_initialize_vx+396>_1__
-@end example
-
-
-@item c
-Regard as an integer and print it as a character constant.
-
-@item f
-Regard the bits of the value as a floating point number and print
-using typical floating point syntax.
-@end table
-
-For example, to print the program counter in hex (@pxref{Registers}), type
-
-@example
-p/x $pc
-@end example
-
-@noindent
-Note that no space is required before the slash; this is because command
-names in _GDBN__ cannot contain a slash.
-
-To reprint the last value in the value history with a different format,
-you can use the @code{print} command with just a format and no
-expression.  For example, @samp{p/x} reprints the last value in hex.
-
-@node Memory, Auto Display, Output formats, Data
-@section Examining Memory
-
-@cindex examining memory
-@table @code
-@kindex x
-@item x/@var{nfu} @var{expr}
-The command @code{x} (for `examine') can be used to examine memory
-without being constrained by your program's data types.  You can specify
-the unit size @var{u} of memory to inspect, and a repeat count @var{n} of how
-many of those units to display.  @code{x} understands the formats
-@var{f} used by @code{print}; two additional formats, @samp{s} (string)
-and @samp{i} (machine instruction) can be used without specifying a unit
-size.
-@end table
-
-For example, @samp{x/3uh 0x54320} is a request to display three halfwords
-(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
-starting at address @code{0x54320}.  @samp{x/4xw $sp} prints the four
-words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
-@pxref{Registers}) in hexadecimal (@samp{x}).
-
-Since the letters indicating unit sizes are all distinct from the
-letters specifying output formats, you don't have to remember whether
-unit size or format comes first; either order will work.  The output
-specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
-
-After the format specification, you supply an expression for the address
-where _GDBN__ is to begin reading from memory.  The expression need not
-have a pointer value (though it may); it is always interpreted as an
-integer address of a byte of memory.  @xref{Expressions} for more
-information on expressions.
-
-These are the memory units @var{u} you can specify with the @code{x}
-command:
-
-@table @code
-@item b
-Examine individual bytes.
-
-@item h
-Examine halfwords (two bytes each).
-
-@item w
-Examine words (four bytes each).
-
-@cindex word
-Many assemblers and cpu designers still use `word' for a 16-bit quantity,
-as a holdover from specific predecessor machines of the 1970's that really
-did use two-byte words.  But more generally the term `word' has always
-referred to the size of quantity that a machine normally operates on and
-stores in its registers.  This is 32 bits for all the machines that _GDBN__
-runs on.
-
-@item g
-Examine giant words (8 bytes).
-@end table
-
-You can combine these unit specifications with any of the formats
-described for @code{print}.  @xref{Output formats}.
-
-@code{x} has two additional output specifications which derive the unit
-size from the data inspected:
-
-@table @code
-@item s
-Print a null-terminated string of characters.  Any explicitly specified
-unit size is ignored; instead, the unit is however many bytes it takes
-to reach a null character (including the null character).
-
-@item i
-Print a machine instruction in assembler syntax (or nearly).  Any
-specified unit size is ignored; the number of bytes in an instruction
-varies depending on the type of machine, the opcode and the addressing
-modes used.  The command @code{disassemble} gives an alternative way of
-inspecting machine instructions.  @xref{Machine Code}.
-@end table
-
-If you omit either the format @var{f} or the unit size @var{u}, @code{x}
-will use the same one that was used last.  If you don't use any letters
-or digits after the slash, you can omit the slash as well.
-
-You can also omit the address to examine.  Then the address used is just
-after the last unit examined.  This is why string and instruction
-formats actually compute a unit-size based on the data: so that the next
-string or instruction examined will start in the right place.  
-
-When the @code{print} command shows a value that resides in memory,
-@code{print} also sets the default address for the @code{x} command.
-@code{info line} also sets the default for @code{x}, to the address of
-the start of the machine code for the specified line (@pxref{Machine
-Code}), and @code{info breakpoints} sets it to the address of the last
-breakpoint listed (@pxref{Set Breaks}).
-
-When you use @key{RET} to repeat an @code{x} command, the address
-specified previously (if any) is ignored, so that the repeated command
-examines the successive locations in memory rather than the same ones.
-
-You can examine several consecutive units of memory with one command by
-writing a repeat-count after the slash (before the format letters, if
-any).  Omitting the repeat count @var{n} displays one unit of the
-appropriate size.  The repeat count must be a decimal integer.  It has
-the same effect as repeating the @code{x} command @var{n} times except
-that the output may be more compact, with several units per line.  For
-example,
-
-@example
-x/10i $pc
-@end example
-
-@noindent
-prints ten instructions starting with the one to be executed next in the
-selected frame.  After doing this, you could print a further seven
-instructions with
-
-@example
-x/7
-@end example
-
-@noindent
----where the format and address are allowed to default.
-
-@kindex $_
-@kindex $__
-The addresses and contents printed by the @code{x} command are not put
-in the value history because there is often too much of them and they
-would get in the way.  Instead, _GDBN__ makes these values available for
-subsequent use in expressions as values of the convenience variables
-@code{$_} and @code{$__}.  After an @code{x} command, the last address
-examined is available for use in expressions in the convenience variable
-@code{$_}.  The contents of that address, as examined, are available in
-the convenience variable @code{$__}.
-
-If the @code{x} command has a repeat count, the address and contents saved
-are from the last memory unit printed; this is not the same as the last
-address printed if several units were printed on the last line of output.
-
-@node Auto Display, Print Settings, Memory, Data
-@section Automatic Display
-@cindex automatic display
-@cindex display of expressions
-
-If you find that you want to print the value of an expression frequently
-(to see how it changes), you might want to add it to the @dfn{automatic
-display list} so that _GDBN__ will print its value each time the program stops.
-Each expression added to the list is given a number to identify it;
-to remove an expression from the list, you specify that number.
-The automatic display looks like this:
-
-@example
-2: foo = 38
-3: bar[5] = (struct hack *) 0x3804
-@end example
-
-@noindent
-showing item numbers, expressions and their current values.  As with
-displays you request manually using @code{x} or @code{print}, you can
-specify the output format you prefer; in fact, @code{display} decides
-whether to use @code{print} or @code{x} depending on how elaborate your
-format specification is---it uses @code{x} if you specify a unit size,
-or one of the two formats (@samp{i} and @samp{s}) that are only
-supported by @code{x}; otherwise it uses @code{print}.
-
-@table @code
-@item display @var{exp}
-@kindex display
-Add the expression @var{exp} to the list of expressions to display
-each time the program stops.  @xref{Expressions}.
-
-@code{display} will not repeat if you press @key{RET} again after using it.
-
-@item display/@var{fmt} @var{exp}
-For @var{fmt} specifying only a display format and not a size or
-count, add the expression @var{exp} to the auto-display list but
-arranges to display it each time in the specified format @var{fmt}.
-@xref{Output formats}.
-
-@item display/@var{fmt} @var{addr}
-For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
-number of units, add the expression @var{addr} as a memory address to
-be examined each time the program stops.  Examining means in effect
-doing @samp{x/@var{fmt} @var{addr}}.  @xref{Memory}.
-@end table
-
-For example, @samp{display/i $pc} can be helpful, to see the machine
-instruction about to be executed each time execution stops (@samp{$pc}
-is a common name for the program counter; @pxref{Registers}).
-
-@table @code
-@item undisplay @var{dnums}@dots{}
-@itemx delete display @var{dnums}@dots{}
-@kindex delete display
-@kindex undisplay
-Remove item numbers @var{dnums} from the list of expressions to display.
-
-@code{undisplay} will not repeat if you press @key{RET} after using it.
-(Otherwise you would just get the error @samp{No display number @dots{}}.)
-
-@item disable display @var{dnums}@dots{}
-@kindex disable display
-Disable the display of item numbers @var{dnums}.  A disabled display
-item is not printed automatically, but is not forgotten.  It may be
-enabled again later.
-
-@item enable display @var{dnums}@dots{}
-@kindex enable display
-Enable display of item numbers @var{dnums}.  It becomes effective once
-again in auto display of its expression, until you specify otherwise.
-
-@item display
-Display the current values of the expressions on the list, just as is
-done when the program stops.
-
-@item info display
-@kindex info display
-Print the list of expressions previously set up to display
-automatically, each one with its item number, but without showing the
-values.  This includes disabled expressions, which are marked as such.
-It also includes expressions which would not be displayed right now
-because they refer to automatic variables not currently available.
-@end table
-
-If a display expression refers to local variables, then it does not make
-sense outside the lexical context for which it was set up.  Such an
-expression is disabled when execution enters a context where one of its
-variables is not defined.  For example, if you give the command
-@code{display last_char} while inside a function with an argument
-@code{last_char}, then this argument will be displayed while the program
-continues to stop inside that function.  When it stops elsewhere---where
-there is no variable @code{last_char}---display is disabled.  The next time
-your program stops where @code{last_char} is meaningful, you can enable the
-display expression once again.
-
-@node Print Settings, Value History, Auto Display, Data
-@section Print Settings
-
-@cindex format options
-@cindex print settings
-_GDBN__ provides the following ways to control how arrays, structures,
-and symbols are printed.  
-
-@noindent
-These settings are useful for debugging programs in any language:
-
-@table @code
-@item set print address
-@item set print address on
-@kindex set print address
-_GDBN__ will print memory addresses showing the location of stack
-traces, structure values, pointer values, breakpoints, and so forth,
-even when it also displays the contents of those addresses.  The default
-is on.  For example, this is what a stack frame display looks like, with
-@code{set print address on}:
-@smallexample
-(_GDBP__) f
-#0  set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") 
-    at input.c:530
-530	    if (lquote != def_lquote)
-@end smallexample
-
-@item set print address off
-Do not print addresses when displaying their contents.  For example,
-this is the same stack frame displayed with @code{set print address off}:
-@example
-(_GDBP__) set print addr off
-(_GDBP__) f
-#0  set_quotes (lq="<<", rq=">>") at input.c:530
-530	    if (lquote != def_lquote)
-@end example
-
-@item show print address
-@kindex show print address
-Show whether or not addresses are to be printed.
-
-@item set print array
-@itemx set print array on
-@kindex set print array
-_GDBN__ will pretty print arrays.  This format is more convenient to read,
-but uses more space.  The default is off.
-
-@item set print array off.
-Return to compressed format for arrays.
-
-@item show print array
-@kindex show print array
-Show whether compressed or pretty format is selected for displaying
-arrays. 
-
-@item set print elements @var{number-of-elements}
-@kindex set print elements
-If _GDBN__ is printing a large array, it will stop printing after it has
-printed the number of elements set by the @code{set print elements} command.
-This limit also applies to the display of strings.
-
-@item show print elements
-@kindex show print elements
-Display the number of elements of a large array that _GDBN__ will print
-before losing patience.
-
-@item set print pretty on
-@kindex set print pretty
-Cause _GDBN__ to print structures in an indented format with one member per
-line, like this:
-
-@example
-$1 = @{
-  next = 0x0,
-  flags = @{
-    sweet = 1,
-    sour = 1
-  @},
-  meat = 0x54 "Pork"
-@}
-@end example
-
-@item set print pretty off
-Cause _GDBN__ to print structures in a compact format, like this:
-
-@smallexample
-$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, meat \
-= 0x54 "Pork"@}
-@end smallexample
-
-@noindent
-This is the default format.
-
-@item show print pretty
-@kindex show print pretty
-Show which format _GDBN__ will use to print structures.
-
-@item set print sevenbit-strings on
-Print using only seven-bit characters; if this option is set, 
-_GDBN__ will display any eight-bit characters (in strings or character
-values) using the notation @code{\}@var{nnn}.  For example, @kbd{M-a} is
-displayed as @code{\341}.
-
-@item set print sevenbit-strings off
-Print using either seven-bit or eight-bit characters, as required.  This
-is the default.
-
-@item show print sevenbit-strings
-Show whether or not _GDBN__ will print only seven-bit characters.
-
-@item set print union on
-@kindex set print union
-Tell _GDBN__ to print unions which are contained in structures.  This is the
-default setting.
-
-@item set print union off
-Tell _GDBN__ not to print unions which are contained in structures.
-
-@item show print union
-@kindex show print union
-Ask _GDBN__ whether or not it will print unions which are contained in
-structures. 
-
-For example, given the declarations
-
-@smallexample
-typedef enum @{Tree, Bug@} Species;
-typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
-typedef enum @{Caterpillar, Cocoon, Butterfly@} Bug_forms;
-
-struct thing @{
-  Species it;
-  union @{
-    Tree_forms tree;
-    Bug_forms bug;
-  @} form;
-@};
-
-struct thing foo = @{Tree, @{Acorn@}@};
-@end smallexample
-
-@noindent
-with @code{set print union on} in effect @samp{p foo} would print
-
-@smallexample
-$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
-@end smallexample
-
-@noindent
-and with @code{set print union off} in effect it would print
-
-@smallexample
-$1 = @{it = Tree, form = @{...@}@}
-@end smallexample
-@end table
-
-@noindent
-These settings are of interest when debugging C++ programs:
-
-@table @code
-@item set print demangle 
-@itemx set print demangle on 
-@kindex set print demangle
-Print C++ names in their source form rather than in the mangled form
-in which they are passed to the assembler and linker for type-safe linkage.
-The default is on.
-
-@item show print demangle
-@kindex show print demangle
-Show whether C++ names will be printed in mangled or demangled form.
-
-@item set print asm-demangle 
-@itemx set print asm-demangle on 
-@kindex set print asm-demangle
-Print C++ names in their source form rather than their mangled form, even
-in assembler code printouts such as instruction disassemblies.
-The default is off.
-
-@item show print asm-demangle
-@kindex show print asm-demangle
-Show whether C++ names in assembly listings will be printed in mangled
-or demangled form.
-
-@item set print object
-@itemx set print object on
-@kindex set print object
-When displaying a pointer to an object, identify the @emph{actual}
-(derived) type of the object rather than the @emph{declared} type, using
-the virtual function table.
-
-@item set print object off
-Display only the declared type of objects, without reference to the
-virtual function table.  This is the default setting.
-
-@item show print object
-@kindex show print object
-Show whether actual, or declared, object types will be displayed.
-
-@item set print vtbl 
-@itemx set print vtbl on 
-@kindex set print vtbl
-Pretty print C++ virtual function tables.  The default is off.
-
-@item set print vtbl off
-Do not pretty print C++ virtual function tables.
-
-@item show print vtbl
-@kindex show print vtbl
-Show whether C++ virtual function tables are pretty printed, or not.
-
-@end table
-
-@node Value History, Convenience Vars, Print Settings, Data
-@section Value History
-
-@cindex value history
-Values printed by the @code{print} command are saved in _GDBN__'s @dfn{value
-history} so that you can refer to them in other expressions.  Values are
-kept until the symbol table is re-read or discarded (for example with
-the @code{file} or @code{symbol-file} commands).  When the symbol table
-changes, the value history is discarded, since the values may contain
-pointers back to the types defined in the symbol table.
-
-@cindex @code{$}
-@cindex @code{$$}
-@cindex history number
-The values printed are given @dfn{history numbers} for you to refer to them
-by.  These are successive integers starting with one.  @code{print} shows you
-the history number assigned to a value by printing @samp{$@var{num} = }
-before the value; here @var{num} is the history number.
-
-To refer to any previous value, use @samp{$} followed by the value's
-history number.  The way @code{print} labels its output is designed to
-remind you of this.  Just @code{$} refers to the most recent value in
-the history, and @code{$$} refers to the value before that.
-@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
-is the value just prior to @code{$$}, @code{$$1} is equivalent to
-@code{$$}, and @code{$$0} is equivalent to @code{$}.
-
-For example, suppose you have just printed a pointer to a structure and
-want to see the contents of the structure.  It suffices to type
-
-@example
-p *$
-@end example
-
-If you have a chain of structures where the component @code{next} points
-to the next one, you can print the contents of the next one with this:
-
-@example
-p *$.next
-@end example
-
-@noindent
-You can print successive links in the chain by repeating this
-command---which you can do by just typing @key{RET}.
-
-Note that the history records values, not expressions.  If the value of
-@code{x} is 4 and you type these commands:
-
-@example
-print x
-set x=5
-@end example
-
-@noindent
-then the value recorded in the value history by the @code{print} command
-remains 4 even though the value of @code{x} has changed.
-
-@table @code
-@kindex show values
-@item show values
-Print the last ten values in the value history, with their item numbers.
-This is like @samp{p@ $$9} repeated ten times, except that @code{show
-values} does not change the history.
-
-@item show values @var{n}
-Print ten history values centered on history item number @var{n}.
-
-@item show values +
-Print ten history values just after the values last printed.  If no more
-values are available, produces no display.
-@end table
-
-Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
-same effect as @samp{show values +}.  
-
-@node Convenience Vars, Registers, Value History, Data
-@section Convenience Variables
-
-@cindex convenience variables
-_GDBN__ provides @dfn{convenience variables} that you can use within
-_GDBN__ to hold on to a value and refer to it later.  These variables
-exist entirely within _GDBN__; they are not part of your program, and
-setting a convenience variable has no direct effect on further execution
-of your program.  That's why you can use them freely.
-
-Convenience variables are prefixed with @samp{$}.  Any name preceded by
-@samp{$} can be used for a convenience variable, unless it is one of
-the predefined machine-specific register names (@pxref{Registers}).
-(Value history references, in contrast, are @emph{numbers} preceded
-by @samp{$}.  @xref{Value History}.)
-
-You can save a value in a convenience variable with an assignment
-expression, just as you would set a variable in your program.  Example:
-
-@example
-set $foo = *object_ptr
-@end example
-
-@noindent
-would save in @code{$foo} the value contained in the object pointed to by
-@code{object_ptr}.
-
-Using a convenience variable for the first time creates it; but its value
-is @code{void} until you assign a new value.  You can alter the value with
-another assignment at any time.
-
-Convenience variables have no fixed types.  You can assign a convenience
-variable any type of value, including structures and arrays, even if
-that variable already has a value of a different type.  The convenience
-variable, when used as an expression, has the type of its current value.
-
-@table @code
-@item show convenience
-@kindex show convenience
-Print a list of convenience variables used so far, and their values.
-Abbreviated @code{show con}.
-@end table
-
-One of the ways to use a convenience variable is as a counter to be
-incremented or a pointer to be advanced.  For example, to print
-a field from successive elements of an array of structures:
-
-_0__@example
-set $i = 0
-print bar[$i++]->contents
-@i{@dots{} repeat that command by typing @key{RET}.}
-_1__@end example
-
-Some convenience variables are created automatically by _GDBN__ and given
-values likely to be useful.
-
-@table @code
-@item $_
-The variable @code{$_} is automatically set by the @code{x} command to
-the last address examined (@pxref{Memory}).  Other commands which
-provide a default address for @code{x} to examine also set @code{$_}
-to that address; these commands include @code{info line} and @code{info
-breakpoint}.
-
-@item $__
-The variable @code{$__} is automatically set by the @code{x} command
-to the value found in the last address examined.
-@end table
-
-@node Registers, Floating Point Hardware, Convenience Vars, Data
-@section Registers
-
-@cindex registers
-Machine register contents can be referred to in expressions as variables
-with names starting with @samp{$}.  The names of registers are different
-for each machine; use @code{info registers} to see the names used on
-your machine.  
-
-@table @code
-@item info registers
-@kindex info registers
-Print the names and values of all registers (in the selected stack frame).
-
-@item info registers @var{regname}
-Print the relativized value of register @var{regname}.  @var{regname}
-may be any register name valid on the machine you are using, with
-or without the initial @samp{$}.
-@end table
-
-The register names @code{$pc} and @code{$sp} are used on most machines
-for the program counter register and the stack pointer.  For example,
-you could print the program counter in hex with
-@example
-p/x $pc
-@end example
-
-@noindent
-or print the instruction to be executed next with
-@example
-x/i $pc
-@end example
-
-@noindent
-or add four to the stack pointer with
-@example
-set $sp += 4
-@end example
-
-@noindent
-The last is a way of removing one word from the stack, on machines where
-stacks grow downward in memory (most machines, nowadays).  This assumes
-that the innermost stack frame is selected; setting @code{$sp} is
-not allowed when other stack frames are selected.  (To pop entire frames
-off the stack, regardless of machine architecture, use @code{return};
-@pxref{Returning}.)
-
-Often @code{$fp} is used for a register that contains a pointer to the
-current stack frame, and @code{$ps} is sometimes used for a register
-that contains the processor status.  These standard register names may
-be available on your machine even though the @code{info registers}
-command shows other names.  For example, on the SPARC, @code{info
-registers} displays the processor status register as @code{$psr} but you
-can also refer to it as @code{$ps}.
-
-_GDBN__ always considers the contents of an ordinary register as an
-integer when the register is examined in this way.  Some machines have
-special registers which can hold nothing but floating point; these
-registers are considered to have floating point values.  There is no way
-to refer to the contents of an ordinary register as floating point value
-(although you can @emph{print} it as a floating point value with
-@samp{print/f $@var{regname}}).
-
-Some registers have distinct ``raw'' and ``virtual'' data formats.  This
-means that the data format in which the register contents are saved by
-the operating system is not the same one that your program normally
-sees.  For example, the registers of the 68881 floating point
-coprocessor are always saved in ``extended'' (raw) format, but all C
-programs expect to work with ``double'' (virtual) format.  In such
-cases, _GDBN__ normally works with the virtual format only (the format that
-makes sense for your program), but the @code{info registers} command
-prints the data in both formats.
-
-Normally, register values are relative to the selected stack frame
-(@pxref{Selection}).  This means that you get the value that the
-register would contain if all stack frames farther in were exited and
-their saved registers restored.  In order to see the true contents of
-hardware registers, you must select the innermost frame (with
-@samp{frame 0}).
-
-However, _GDBN__ must deduce where registers are saved, from the machine
-code generated by your compiler.  If some registers are not saved, or if
-_GDBN__ is unable to locate the saved registers, the selected stack
-frame will make no difference.
-
-@node Floating Point Hardware,  , Registers, Data
-@section Floating Point Hardware
-@cindex floating point
-Depending on the host machine architecture, _GDBN__ may be able to give
-you more information about the status of the floating point hardware.
-
-@table @code
-@item info float
-@kindex info float
-If available, provides hardware-dependent information about the floating
-point unit.  The exact contents and layout vary depending on the
-floating point chip.
-@end table
-@c FIXME: this is a cop-out.  Try to get examples, explanations.  Only
-@c FIXME...supported currently on arm's and 386's.  Mark properly with 
-@c FIXME... m4 macros to isolate general statements from hardware-dep, 
-@c FIXME... at that point.