extend.texi (Variable Attributes): Add menu and proper @nodes to subsections.
2015-05-01 Sandra Loosemore <sandra@codesourcery.com> gcc/ * doc/extend.texi (Variable Attributes): Add menu and proper @nodes to subsections. Move Microsoft Windows attributes to their own subsection. (Type Attributes): Reorganize introduction to remove duplicate list of attributes. Add menu and proper @nodes to subsections. Alphabetize the main table of common attributes. From-SVN: r222714
This commit is contained in:
Sandra Loosemore
Sandra Loosemore
parent
9c0717ed3f
commit
90eb63a3a0
2 changed files with 262 additions and 205 deletions
|
|
@ -1,3 +1,12 @@
|
|||
2015-05-01 Sandra Loosemore <sandra@codesourcery.com>
|
||||
|
||||
* doc/extend.texi (Variable Attributes): Add menu and proper
|
||||
@nodes to subsections. Move Microsoft Windows attributes to
|
||||
their own subsection.
|
||||
(Type Attributes): Reorganize introduction to remove duplicate
|
||||
list of attributes. Add menu and proper @nodes to subsections.
|
||||
Alphabetize the main table of common attributes.
|
||||
|
||||
2015-05-01 Rasmus Villemoes <rv@rasmusvillemoes.dk>
|
||||
|
||||
* match.pd: New simplification patterns.
|
||||
|
|
|
|||
|
|
@ -5400,6 +5400,26 @@ Other front ends might define more attributes
|
|||
@xref{Attribute Syntax}, for details of the exact syntax for using
|
||||
attributes.
|
||||
|
||||
@menu
|
||||
* Common Variable Attributes::
|
||||
* AVR Variable Attributes::
|
||||
* Blackfin Variable Attributes::
|
||||
* H8/300 Variable Attributes::
|
||||
* IA-64 Variable Attributes::
|
||||
* M32R/D Variable Attributes::
|
||||
* MeP Variable Attributes::
|
||||
* Microsoft Windows Variable Attributes::
|
||||
* PowerPC Variable Attributes::
|
||||
* SPU Variable Attributes::
|
||||
* x86 Variable Attributes::
|
||||
* Xstormy16 Variable Attributes::
|
||||
@end menu
|
||||
|
||||
@node Common Variable Attributes
|
||||
@subsection Common Variable Attributes
|
||||
|
||||
The following attributes are supported on most targets.
|
||||
|
||||
@table @code
|
||||
@cindex @code{aligned} variable attribute
|
||||
@item aligned (@var{alignment})
|
||||
|
|
@ -5522,7 +5542,8 @@ argument, which must be a string, is printed in the warning if
|
|||
present.
|
||||
|
||||
The @code{deprecated} attribute can also be used for functions and
|
||||
types (@pxref{Common Function Attributes}, @pxref{Type Attributes}).
|
||||
types (@pxref{Common Function Attributes},
|
||||
@pxref{Common Type Attributes}).
|
||||
|
||||
@item mode (@var{mode})
|
||||
@cindex @code{mode} variable attribute
|
||||
|
|
@ -5608,33 +5629,6 @@ attribute is not available on all platforms.
|
|||
If you need to map the entire contents of a module to a particular
|
||||
section, consider using the facilities of the linker instead.
|
||||
|
||||
@item shared
|
||||
@cindex @code{shared} variable attribute
|
||||
On Microsoft Windows, in addition to putting variable definitions in a named
|
||||
section, the section can also be shared among all running copies of an
|
||||
executable or DLL@. For example, this small program defines shared data
|
||||
by putting it in a named section @code{shared} and marking the section
|
||||
shareable:
|
||||
|
||||
@smallexample
|
||||
int foo __attribute__((section ("shared"), shared)) = 0;
|
||||
|
||||
int
|
||||
main()
|
||||
@{
|
||||
/* @r{Read and write foo. All running
|
||||
copies see the same value.} */
|
||||
return 0;
|
||||
@}
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
You may only use the @code{shared} attribute along with @code{section}
|
||||
attribute with a fully-initialized global definition because of the way
|
||||
linkers work. See @code{section} attribute for more information.
|
||||
|
||||
The @code{shared} attribute is only available on Microsoft Windows@.
|
||||
|
||||
@item tls_model ("@var{tls_model}")
|
||||
@cindex @code{tls_model} variable attribute
|
||||
The @code{tls_model} attribute sets thread-local storage model
|
||||
|
|
@ -5692,45 +5686,14 @@ struct S __attribute__ ((vector_size (16))) foo;
|
|||
is invalid even if the size of the structure is the same as the size of
|
||||
the @code{int}.
|
||||
|
||||
@item selectany
|
||||
@cindex @code{selectany} variable attribute
|
||||
The @code{selectany} attribute causes an initialized global variable to
|
||||
have link-once semantics. When multiple definitions of the variable are
|
||||
encountered by the linker, the first is selected and the remainder are
|
||||
discarded. Following usage by the Microsoft compiler, the linker is told
|
||||
@emph{not} to warn about size or content differences of the multiple
|
||||
definitions.
|
||||
|
||||
Although the primary usage of this attribute is for POD types, the
|
||||
attribute can also be applied to global C++ objects that are initialized
|
||||
by a constructor. In this case, the static initialization and destruction
|
||||
code for the object is emitted in each translation defining the object,
|
||||
but the calls to the constructor and destructor are protected by a
|
||||
link-once guard variable.
|
||||
|
||||
The @code{selectany} attribute is only available on Microsoft Windows
|
||||
targets. You can use @code{__declspec (selectany)} as a synonym for
|
||||
@code{__attribute__ ((selectany))} for compatibility with other
|
||||
compilers.
|
||||
|
||||
@item weak
|
||||
@cindex @code{weak} variable attribute
|
||||
The @code{weak} attribute is described in
|
||||
@ref{Common Function Attributes}.
|
||||
|
||||
@item dllimport
|
||||
@cindex @code{dllimport} variable attribute
|
||||
The @code{dllimport} attribute is described in
|
||||
@ref{Microsoft Windows Function Attributes}.
|
||||
|
||||
@item dllexport
|
||||
@cindex @code{dllexport} variable attribute
|
||||
The @code{dllexport} attribute is described in
|
||||
@ref{Microsoft Windows Function Attributes}.
|
||||
|
||||
@end table
|
||||
|
||||
@anchor{AVR Variable Attributes}
|
||||
@node AVR Variable Attributes
|
||||
@subsection AVR Variable Attributes
|
||||
|
||||
@table @code
|
||||
|
|
@ -5813,6 +5776,7 @@ volatile int porta __attribute__((address (0x600)));
|
|||
|
||||
@end table
|
||||
|
||||
@node Blackfin Variable Attributes
|
||||
@subsection Blackfin Variable Attributes
|
||||
|
||||
Three attributes are currently defined for the Blackfin.
|
||||
|
|
@ -5837,6 +5801,7 @@ Variables with @code{l2} attribute are put into the specific section
|
|||
named @code{.l2.data}.
|
||||
@end table
|
||||
|
||||
@node H8/300 Variable Attributes
|
||||
@subsection H8/300 Variable Attributes
|
||||
|
||||
These variable attributes are available for H8/300 targets:
|
||||
|
|
@ -5865,6 +5830,7 @@ slightly under 32KB of data.
|
|||
|
||||
@end table
|
||||
|
||||
@node IA-64 Variable Attributes
|
||||
@subsection IA-64 Variable Attributes
|
||||
|
||||
The IA-64 back end supports the following variable attribute:
|
||||
|
|
@ -5883,6 +5849,7 @@ defined by shared libraries.
|
|||
|
||||
@end table
|
||||
|
||||
@node M32R/D Variable Attributes
|
||||
@subsection M32R/D Variable Attributes
|
||||
|
||||
One attribute is currently defined for the M32R/D@.
|
||||
|
|
@ -5903,7 +5870,7 @@ Medium and large model objects may live anywhere in the 32-bit address space
|
|||
addresses).
|
||||
@end table
|
||||
|
||||
@anchor{MeP Variable Attributes}
|
||||
@node MeP Variable Attributes
|
||||
@subsection MeP Variable Attributes
|
||||
|
||||
The MeP target has a number of addressing modes and busses. The
|
||||
|
|
@ -5967,6 +5934,72 @@ int cpu_clock __attribute__((cb(0x123)));
|
|||
|
||||
@end table
|
||||
|
||||
@node Microsoft Windows Variable Attributes
|
||||
@subsection Microsoft Windows Variable Attributes
|
||||
|
||||
You can use these attributes on Microsoft Windows targets.
|
||||
@ref{x86 Variable Attributes} for additional Windows compatibility
|
||||
attributes available on all x86 targets.
|
||||
|
||||
@table @code
|
||||
@item dllimport
|
||||
@itemx dllexport
|
||||
@cindex @code{dllimport} variable attribute
|
||||
@cindex @code{dllexport} variable attribute
|
||||
The @code{dllimport} and @code{dllexport} attributes are described in
|
||||
@ref{Microsoft Windows Function Attributes}.
|
||||
|
||||
@item selectany
|
||||
@cindex @code{selectany} variable attribute
|
||||
The @code{selectany} attribute causes an initialized global variable to
|
||||
have link-once semantics. When multiple definitions of the variable are
|
||||
encountered by the linker, the first is selected and the remainder are
|
||||
discarded. Following usage by the Microsoft compiler, the linker is told
|
||||
@emph{not} to warn about size or content differences of the multiple
|
||||
definitions.
|
||||
|
||||
Although the primary usage of this attribute is for POD types, the
|
||||
attribute can also be applied to global C++ objects that are initialized
|
||||
by a constructor. In this case, the static initialization and destruction
|
||||
code for the object is emitted in each translation defining the object,
|
||||
but the calls to the constructor and destructor are protected by a
|
||||
link-once guard variable.
|
||||
|
||||
The @code{selectany} attribute is only available on Microsoft Windows
|
||||
targets. You can use @code{__declspec (selectany)} as a synonym for
|
||||
@code{__attribute__ ((selectany))} for compatibility with other
|
||||
compilers.
|
||||
|
||||
@item shared
|
||||
@cindex @code{shared} variable attribute
|
||||
On Microsoft Windows, in addition to putting variable definitions in a named
|
||||
section, the section can also be shared among all running copies of an
|
||||
executable or DLL@. For example, this small program defines shared data
|
||||
by putting it in a named section @code{shared} and marking the section
|
||||
shareable:
|
||||
|
||||
@smallexample
|
||||
int foo __attribute__((section ("shared"), shared)) = 0;
|
||||
|
||||
int
|
||||
main()
|
||||
@{
|
||||
/* @r{Read and write foo. All running
|
||||
copies see the same value.} */
|
||||
return 0;
|
||||
@}
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
You may only use the @code{shared} attribute along with @code{section}
|
||||
attribute with a fully-initialized global definition because of the way
|
||||
linkers work. See @code{section} attribute for more information.
|
||||
|
||||
The @code{shared} attribute is only available on Microsoft Windows@.
|
||||
|
||||
@end table
|
||||
|
||||
@node PowerPC Variable Attributes
|
||||
@subsection PowerPC Variable Attributes
|
||||
|
||||
Three attributes currently are defined for PowerPC configurations:
|
||||
|
|
@ -5981,6 +6014,7 @@ documentation in @ref{x86 Variable Attributes}.
|
|||
For documentation of @code{altivec} attribute please see the
|
||||
documentation in @ref{PowerPC Type Attributes}.
|
||||
|
||||
@node SPU Variable Attributes
|
||||
@subsection SPU Variable Attributes
|
||||
|
||||
@cindex @code{spu_vector} variable attribute, SPU
|
||||
|
|
@ -5988,7 +6022,7 @@ The SPU supports the @code{spu_vector} attribute for variables. For
|
|||
documentation of this attribute please see the documentation in
|
||||
@ref{SPU Type Attributes}.
|
||||
|
||||
@anchor{x86 Variable Attributes}
|
||||
@node x86 Variable Attributes
|
||||
@subsection x86 Variable Attributes
|
||||
|
||||
Two attributes are currently defined for x86 configurations:
|
||||
|
|
@ -6126,6 +6160,7 @@ Here, @code{t5} takes up 2 bytes.
|
|||
@end enumerate
|
||||
@end table
|
||||
|
||||
@node Xstormy16 Variable Attributes
|
||||
@subsection Xstormy16 Variable Attributes
|
||||
|
||||
One attribute is currently defined for xstormy16 configurations:
|
||||
|
|
@ -6149,27 +6184,39 @@ placed in either the @code{.bss_below100} section or the
|
|||
@cindex type attributes
|
||||
|
||||
The keyword @code{__attribute__} allows you to specify special
|
||||
attributes of @code{struct} and @code{union} types when you define
|
||||
such types. This keyword is followed by an attribute specification
|
||||
inside double parentheses. Eight attributes are currently defined for
|
||||
types: @code{aligned}, @code{packed}, @code{transparent_union},
|
||||
@code{unused}, @code{deprecated}, @code{visibility}, @code{may_alias}
|
||||
and @code{bnd_variable_size}. Other attributes are defined for
|
||||
attributes of types. Some type attributes apply only to @code{struct}
|
||||
and @code{union} types, while others can apply to any type defined
|
||||
via a @code{typedef} declaration. Other attributes are defined for
|
||||
functions (@pxref{Function Attributes}), labels (@pxref{Label
|
||||
Attributes}) and for variables (@pxref{Variable Attributes}).
|
||||
|
||||
The @code{__attribute__} keyword is followed by an attribute specification
|
||||
inside double parentheses.
|
||||
|
||||
You may specify type attributes in an enum, struct or union type
|
||||
declaration or definition, or for other types in a @code{typedef}
|
||||
declaration.
|
||||
|
||||
For an enum, struct or union type, you may specify attributes either
|
||||
between the enum, struct or union tag and the name of the type, or
|
||||
just past the closing curly brace of the @emph{definition}. The
|
||||
former syntax is preferred.
|
||||
declaration or definition by placing them immediately after the
|
||||
@code{struct}, @code{union} or @code{enum} keyword. A less preferred
|
||||
syntax is to place them just past the closing curly brace of the
|
||||
definition.
|
||||
|
||||
You can also include type attributes in a @code{typedef} declaration.
|
||||
@xref{Attribute Syntax}, for details of the exact syntax for using
|
||||
attributes.
|
||||
|
||||
@menu
|
||||
* Common Type Attributes::
|
||||
* ARM Type Attributes::
|
||||
* MeP Type Attributes::
|
||||
* PowerPC Type Attributes::
|
||||
* SPU Type Attributes::
|
||||
* x86 Type Attributes::
|
||||
@end menu
|
||||
|
||||
@node Common Type Attributes
|
||||
@subsection Common Type Attributes
|
||||
|
||||
The following type attributes are supported on most targets.
|
||||
|
||||
@table @code
|
||||
@cindex @code{aligned} type attribute
|
||||
@item aligned (@var{alignment})
|
||||
|
|
@ -6250,14 +6297,6 @@ up to a maximum of 8-byte alignment, then specifying @code{aligned(16)}
|
|||
in an @code{__attribute__} still only provides you with 8-byte
|
||||
alignment. See your linker documentation for further information.
|
||||
|
||||
@item packed
|
||||
@cindex @code{packed} type attribute
|
||||
This attribute, attached to @code{struct} or @code{union} type
|
||||
definition, specifies that each member (other than zero-width bit-fields)
|
||||
of the structure or union is placed to minimize the memory required. When
|
||||
attached to an @code{enum} definition, it indicates that the smallest
|
||||
integral type should be used.
|
||||
|
||||
@opindex fshort-enums
|
||||
Specifying this attribute for @code{struct} and @code{union} types is
|
||||
equivalent to specifying the @code{packed} attribute on each of the
|
||||
|
|
@ -6289,6 +6328,132 @@ You may only specify this attribute on the definition of an @code{enum},
|
|||
@code{struct} or @code{union}, not on a @code{typedef} that does not
|
||||
also define the enumerated type, structure or union.
|
||||
|
||||
@item bnd_variable_size
|
||||
@cindex @code{bnd_variable_size} type attribute
|
||||
@cindex Pointer Bounds Checker attributes
|
||||
When applied to a structure field, this attribute tells Pointer
|
||||
Bounds Checker that the size of this field should not be computed
|
||||
using static type information. It may be used to mark variably-sized
|
||||
static array fields placed at the end of a structure.
|
||||
|
||||
@smallexample
|
||||
struct S
|
||||
@{
|
||||
int size;
|
||||
char data[1];
|
||||
@}
|
||||
S *p = (S *)malloc (sizeof(S) + 100);
|
||||
p->data[10] = 0; //Bounds violation
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
By using an attribute for the field we may avoid unwanted bound
|
||||
violation checks:
|
||||
|
||||
@smallexample
|
||||
struct S
|
||||
@{
|
||||
int size;
|
||||
char data[1] __attribute__((bnd_variable_size));
|
||||
@}
|
||||
S *p = (S *)malloc (sizeof(S) + 100);
|
||||
p->data[10] = 0; //OK
|
||||
@end smallexample
|
||||
|
||||
@item deprecated
|
||||
@itemx deprecated (@var{msg})
|
||||
@cindex @code{deprecated} type attribute
|
||||
The @code{deprecated} attribute results in a warning if the type
|
||||
is used anywhere in the source file. This is useful when identifying
|
||||
types that are expected to be removed in a future version of a program.
|
||||
If possible, the warning also includes the location of the declaration
|
||||
of the deprecated type, to enable users to easily find further
|
||||
information about why the type is deprecated, or what they should do
|
||||
instead. Note that the warnings only occur for uses and then only
|
||||
if the type is being applied to an identifier that itself is not being
|
||||
declared as deprecated.
|
||||
|
||||
@smallexample
|
||||
typedef int T1 __attribute__ ((deprecated));
|
||||
T1 x;
|
||||
typedef T1 T2;
|
||||
T2 y;
|
||||
typedef T1 T3 __attribute__ ((deprecated));
|
||||
T3 z __attribute__ ((deprecated));
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
results in a warning on line 2 and 3 but not lines 4, 5, or 6. No
|
||||
warning is issued for line 4 because T2 is not explicitly
|
||||
deprecated. Line 5 has no warning because T3 is explicitly
|
||||
deprecated. Similarly for line 6. The optional @var{msg}
|
||||
argument, which must be a string, is printed in the warning if
|
||||
present.
|
||||
|
||||
The @code{deprecated} attribute can also be used for functions and
|
||||
variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
|
||||
|
||||
@item designated_init
|
||||
@cindex @code{designated_init} type attribute
|
||||
This attribute may only be applied to structure types. It indicates
|
||||
that any initialization of an object of this type must use designated
|
||||
initializers rather than positional initializers. The intent of this
|
||||
attribute is to allow the programmer to indicate that a structure's
|
||||
layout may change, and that therefore relying on positional
|
||||
initialization will result in future breakage.
|
||||
|
||||
GCC emits warnings based on this attribute by default; use
|
||||
@option{-Wno-designated-init} to suppress them.
|
||||
|
||||
@item may_alias
|
||||
@cindex @code{may_alias} type attribute
|
||||
Accesses through pointers to types with this attribute are not subject
|
||||
to type-based alias analysis, but are instead assumed to be able to alias
|
||||
any other type of objects.
|
||||
In the context of section 6.5 paragraph 7 of the C99 standard,
|
||||
an lvalue expression
|
||||
dereferencing such a pointer is treated like having a character type.
|
||||
See @option{-fstrict-aliasing} for more information on aliasing issues.
|
||||
This extension exists to support some vector APIs, in which pointers to
|
||||
one vector type are permitted to alias pointers to a different vector type.
|
||||
|
||||
Note that an object of a type with this attribute does not have any
|
||||
special semantics.
|
||||
|
||||
Example of use:
|
||||
|
||||
@smallexample
|
||||
typedef short __attribute__((__may_alias__)) short_a;
|
||||
|
||||
int
|
||||
main (void)
|
||||
@{
|
||||
int a = 0x12345678;
|
||||
short_a *b = (short_a *) &a;
|
||||
|
||||
b[1] = 0;
|
||||
|
||||
if (a == 0x12345678)
|
||||
abort();
|
||||
|
||||
exit(0);
|
||||
@}
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
If you replaced @code{short_a} with @code{short} in the variable
|
||||
declaration, the above program would abort when compiled with
|
||||
@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
|
||||
above.
|
||||
|
||||
@item packed
|
||||
@cindex @code{packed} type attribute
|
||||
This attribute, attached to @code{struct} or @code{union} type
|
||||
definition, specifies that each member (other than zero-width bit-fields)
|
||||
of the structure or union is placed to minimize the memory required. When
|
||||
attached to an @code{enum} definition, it indicates that the smallest
|
||||
integral type should be used.
|
||||
|
||||
@item transparent_union
|
||||
@cindex @code{transparent_union} type attribute
|
||||
|
||||
|
|
@ -6361,80 +6526,6 @@ the case with lock or thread classes, which are usually defined and then
|
|||
not referenced, but contain constructors and destructors that have
|
||||
nontrivial bookkeeping functions.
|
||||
|
||||
@item deprecated
|
||||
@itemx deprecated (@var{msg})
|
||||
@cindex @code{deprecated} type attribute
|
||||
The @code{deprecated} attribute results in a warning if the type
|
||||
is used anywhere in the source file. This is useful when identifying
|
||||
types that are expected to be removed in a future version of a program.
|
||||
If possible, the warning also includes the location of the declaration
|
||||
of the deprecated type, to enable users to easily find further
|
||||
information about why the type is deprecated, or what they should do
|
||||
instead. Note that the warnings only occur for uses and then only
|
||||
if the type is being applied to an identifier that itself is not being
|
||||
declared as deprecated.
|
||||
|
||||
@smallexample
|
||||
typedef int T1 __attribute__ ((deprecated));
|
||||
T1 x;
|
||||
typedef T1 T2;
|
||||
T2 y;
|
||||
typedef T1 T3 __attribute__ ((deprecated));
|
||||
T3 z __attribute__ ((deprecated));
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
results in a warning on line 2 and 3 but not lines 4, 5, or 6. No
|
||||
warning is issued for line 4 because T2 is not explicitly
|
||||
deprecated. Line 5 has no warning because T3 is explicitly
|
||||
deprecated. Similarly for line 6. The optional @var{msg}
|
||||
argument, which must be a string, is printed in the warning if
|
||||
present.
|
||||
|
||||
The @code{deprecated} attribute can also be used for functions and
|
||||
variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
|
||||
|
||||
@item may_alias
|
||||
@cindex @code{may_alias} type attribute
|
||||
Accesses through pointers to types with this attribute are not subject
|
||||
to type-based alias analysis, but are instead assumed to be able to alias
|
||||
any other type of objects.
|
||||
In the context of section 6.5 paragraph 7 of the C99 standard,
|
||||
an lvalue expression
|
||||
dereferencing such a pointer is treated like having a character type.
|
||||
See @option{-fstrict-aliasing} for more information on aliasing issues.
|
||||
This extension exists to support some vector APIs, in which pointers to
|
||||
one vector type are permitted to alias pointers to a different vector type.
|
||||
|
||||
Note that an object of a type with this attribute does not have any
|
||||
special semantics.
|
||||
|
||||
Example of use:
|
||||
|
||||
@smallexample
|
||||
typedef short __attribute__((__may_alias__)) short_a;
|
||||
|
||||
int
|
||||
main (void)
|
||||
@{
|
||||
int a = 0x12345678;
|
||||
short_a *b = (short_a *) &a;
|
||||
|
||||
b[1] = 0;
|
||||
|
||||
if (a == 0x12345678)
|
||||
abort();
|
||||
|
||||
exit(0);
|
||||
@}
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
If you replaced @code{short_a} with @code{short} in the variable
|
||||
declaration, the above program would abort when compiled with
|
||||
@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
|
||||
above.
|
||||
|
||||
@item visibility
|
||||
@cindex @code{visibility} type attribute
|
||||
In C++, attribute visibility (@pxref{Function Attributes}) can also be
|
||||
|
|
@ -6449,56 +6540,13 @@ and caught in another, the class must have default visibility.
|
|||
Otherwise the two shared objects are unable to use the same
|
||||
typeinfo node and exception handling will break.
|
||||
|
||||
@item designated_init
|
||||
@cindex @code{designated_init} type attribute
|
||||
This attribute may only be applied to structure types. It indicates
|
||||
that any initialization of an object of this type must use designated
|
||||
initializers rather than positional initializers. The intent of this
|
||||
attribute is to allow the programmer to indicate that a structure's
|
||||
layout may change, and that therefore relying on positional
|
||||
initialization will result in future breakage.
|
||||
|
||||
GCC emits warnings based on this attribute by default; use
|
||||
@option{-Wno-designated-init} to suppress them.
|
||||
|
||||
@item bnd_variable_size
|
||||
@cindex @code{bnd_variable_size} type attribute
|
||||
@cindex Pointer Bounds Checker attributes
|
||||
When applied to a structure field, this attribute tells Pointer
|
||||
Bounds Checker that the size of this field should not be computed
|
||||
using static type information. It may be used to mark variably-sized
|
||||
static array fields placed at the end of a structure.
|
||||
|
||||
@smallexample
|
||||
struct S
|
||||
@{
|
||||
int size;
|
||||
char data[1];
|
||||
@}
|
||||
S *p = (S *)malloc (sizeof(S) + 100);
|
||||
p->data[10] = 0; //Bounds violation
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
By using an attribute for the field we may avoid unwanted bound
|
||||
violation checks:
|
||||
|
||||
@smallexample
|
||||
struct S
|
||||
@{
|
||||
int size;
|
||||
char data[1] __attribute__((bnd_variable_size));
|
||||
@}
|
||||
S *p = (S *)malloc (sizeof(S) + 100);
|
||||
p->data[10] = 0; //OK
|
||||
@end smallexample
|
||||
|
||||
@end table
|
||||
|
||||
To specify multiple attributes, separate them by commas within the
|
||||
double parentheses: for example, @samp{__attribute__ ((aligned (16),
|
||||
packed))}.
|
||||
|
||||
@node ARM Type Attributes
|
||||
@subsection ARM Type Attributes
|
||||
|
||||
@cindex @code{notshared} type attribute, ARM
|
||||
|
|
@ -6524,7 +6572,7 @@ virtual table for @code{C} is not exported. (You can use
|
|||
@code{__attribute__} instead of @code{__declspec} if you prefer, but
|
||||
most Symbian OS code uses @code{__declspec}.)
|
||||
|
||||
@anchor{MeP Type Attributes}
|
||||
@node MeP Type Attributes
|
||||
@subsection MeP Type Attributes
|
||||
|
||||
@cindex @code{based} type attribute, MeP
|
||||
|
|
@ -6536,7 +6584,7 @@ Specifically, the @code{based}, @code{tiny}, @code{near}, and
|
|||
@code{far} attributes may be applied to either. The @code{io} and
|
||||
@code{cb} attributes may not be applied to types.
|
||||
|
||||
@anchor{PowerPC Type Attributes}
|
||||
@node PowerPC Type Attributes
|
||||
@subsection PowerPC Type Attributes
|
||||
|
||||
Three attributes currently are defined for PowerPC configurations:
|
||||
|
|
@ -6563,7 +6611,7 @@ __attribute__((altivec(bool__))) unsigned
|
|||
These attributes mainly are intended to support the @code{__vector},
|
||||
@code{__pixel}, and @code{__bool} AltiVec keywords.
|
||||
|
||||
@anchor{SPU Type Attributes}
|
||||
@node SPU Type Attributes
|
||||
@subsection SPU Type Attributes
|
||||
|
||||
@cindex @code{spu_vector} type attribute, SPU
|
||||
|
|
@ -6572,7 +6620,7 @@ allows one to declare vector data types supported by the Sony/Toshiba/IBM SPU
|
|||
Language Extensions Specification. It is intended to support the
|
||||
@code{__vector} keyword.
|
||||
|
||||
@anchor{x86 Type Attributes}
|
||||
@node x86 Type Attributes
|
||||
@subsection x86 Type Attributes
|
||||
|
||||
Two attributes are currently defined for x86 configurations:
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue