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* gdb.texinfo (whatis, ptype): Highlight their differences.  Describe
	typedefs unrolling.  Extend the sample code by an inner typedef and
	outer typedefs unrolling.
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Jan Kratochvil 2011-07-26 16:59:23 +00:00
parent 04aed65246
commit 177bc8396e
2 changed files with 66 additions and 15 deletions
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gdb/doc/ChangeLog
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@ -1,3 +1,10 @@
2011-07-26 Jan Kratochvil <jan.kratochvil@redhat.com>
Eli Zaretskii <eliz@gnu.org>
* gdb.texinfo (whatis, ptype): Highlight their differences. Describe
typedefs unrolling. Extend the sample code by an inner typedef and
outer typedefs unrolling.
2011-07-26 Paul Pluzhnikov <ppluzhnikov@google.com>
* gdb.texinfo (Caching Remote Data): Document {set,show} dcache

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gdb/doc/gdb.texinfo
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@ -13895,16 +13895,34 @@ __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
@kindex whatis
@item whatis [@var{arg}]
Print the data type of @var{arg}, which can be either an expression or
a data type. With no argument, print the data type of @code{$}, the
last value in the value history. If @var{arg} is an expression, it is
not actually evaluated, and any side-effecting operations (such as
assignments or function calls) inside it do not take place. If
@var{arg} is a type name, it may be the name of a type or typedef, or
for C code it may have the form @samp{class @var{class-name}},
@samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
@samp{enum @var{enum-tag}}.
@xref{Expressions, ,Expressions}.
Print the data type of @var{arg}, which can be either an expression
or a name of a data type. With no argument, print the data type of
@code{$}, the last value in the value history.
If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
is not actually evaluated, and any side-effecting operations (such as
assignments or function calls) inside it do not take place.
If @var{arg} is a variable or an expression, @code{whatis} prints its
literal type as it is used in the source code. If the type was
defined using a @code{typedef}, @code{whatis} will @emph{not} print
the data type underlying the @code{typedef}. If the type of the
variable or the expression is a compound data type, such as
@code{struct} or @code{class}, @code{whatis} never prints their
fields or methods. It just prints the @code{struct}/@code{class}
name (a.k.a.@: its @dfn{tag}). If you want to see the members of
such a compound data type, use @code{ptype}.
If @var{arg} is a type name that was defined using @code{typedef},
@code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
Unrolling means that @code{whatis} will show the underlying type used
in the @code{typedef} declaration of @var{arg}. However, if that
underlying type is also a @code{typedef}, @code{whatis} will not
unroll it.
For C code, the type names may also have the form @samp{class
@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
@var{union-tag}} or @samp{enum @var{enum-tag}}.
@kindex ptype
@item ptype [@var{arg}]
@ -13912,10 +13930,23 @@ for C code it may have the form @samp{class @var{class-name}},
detailed description of the type, instead of just the name of the type.
@xref{Expressions, ,Expressions}.
Contrary to @code{whatis}, @code{ptype} always unrolls any
@code{typedef}s in its argument declaration, whether the argument is
a variable, expression, or a data type. This means that @code{ptype}
of a variable or an expression will not print literally its type as
present in the source code---use @code{whatis} for that. @code{typedef}s at
the pointer or reference targets are also unrolled. Only @code{typedef}s of
fields, methods and inner @code{class typedef}s of @code{struct}s,
@code{class}es and @code{union}s are not unrolled even with @code{ptype}.
For example, for this variable declaration:
@smallexample
struct complex @{double real; double imag;@} v;
typedef double real_t;
struct complex @{ real_t real; double imag; @};
typedef struct complex complex_t;
complex_t var;
real_t *real_pointer_var;
@end smallexample
@noindent
@ -13923,13 +13954,26 @@ the two commands give this output:
@smallexample
@group
(@value{GDBP}) whatis v
type = struct complex
(@value{GDBP}) ptype v
(@value{GDBP}) whatis var
type = complex_t
(@value{GDBP}) ptype var
type = struct complex @{
double real;
real_t real;
double imag;
@}
(@value{GDBP}) whatis complex_t
type = struct complex
(@value{GDBP}) whatis struct complex
type = struct complex
(@value{GDBP}) ptype struct complex
type = struct complex @{
real_t real;
double imag;
@}
(@value{GDBP}) whatis real_pointer_var
type = real_t *
(@value{GDBP}) ptype real_pointer_var
type = double *
@end group
@end smallexample