Not all ELF targets support this attribute.
-@item tls_model ("@var{tls_model}")
-@cindex @code{tls_model} attribute
-The @code{tls_model} attribute sets thread-local storage model
-(@pxref{Thread-Local}) of a particular @code{__thread} variable,
-overriding @code{-ftls-model=} command line switch on a per-variable
-basis.
-The @var{tls_model} argument should be one of @code{global-dynamic},
-@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
-
@item regparm (@var{number})
@cindex functions that are passed arguments in registers on the 386
On the Intel 386, the @code{regparm} attribute causes the compiler to
The keyword @code{__attribute__} allows you to specify special
attributes of variables or structure fields. This keyword is followed
-by an attribute specification inside double parentheses. Ten
-attributes are currently defined for variables: @code{aligned},
-@code{mode}, @code{nocommon}, @code{packed}, @code{section},
-@code{transparent_union}, @code{unused}, @code{deprecated},
-@code{vector_size}, and @code{weak}. Some other attributes are defined
-for variables on particular target systems. Other attributes are
-available for functions (@pxref{Function Attributes}) and for types
-(@pxref{Type Attributes}). Other front ends might define more
-attributes (@pxref{C++ Extensions,,Extensions to the C++ Language}).
+by an attribute specification inside double parentheses. Some
+attributes are currently defined generically for variables.
+Other attributes are defined for variables on particular target
+systems. Other attributes are available for functions
+(@pxref{Function Attributes}) and for types (@pxref{Type Attributes}).
+Other front ends might define more attributes
+(@pxref{C++ Extensions,,Extensions to the C++ Language}).
You may also specify attributes with @samp{__} preceding and following
each keyword. This allows you to use them in header files without
in an @code{__attribute__} will still only provide you with 8 byte
alignment. See your linker documentation for further information.
+@item common
+@itemx nocommon
+@cindex @code{common} attribute
+@cindex @code{nocommon} attribute
+@opindex fcommon
+@opindex fno-common
+The @code{common} attribute requests GCC to place a variable in
+``common'' storage. The @code{nocommon} attribute requests the
+opposite -- to allocate space for it directly.
+
+These attributes override the default chosen by the
+@option{-fno-common} and @option{-fcommon} flags respectively.
+
+@item deprecated
+@cindex @code{deprecated} attribute
+The @code{deprecated} attribute results in a warning if the variable
+is used anywhere in the source file. This is useful when identifying
+variables that are expected to be removed in a future version of a
+program. The warning also includes the location of the declaration
+of the deprecated variable, to enable users to easily find further
+information about why the variable is deprecated, or what they should
+do instead. Note that the warnings only occurs for uses:
+
+@smallexample
+extern int old_var __attribute__ ((deprecated));
+extern int old_var;
+int new_fn () @{ return old_var; @}
+@end smallexample
+
+results in a warning on line 3 but not line 2.
+
+The @code{deprecated} attribute can also be used for functions and
+types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
+
@item mode (@var{mode})
@cindex @code{mode} attribute
This attribute specifies the data type for the declaration---whichever
@samp{__word__} for the mode of a one-word integer, and @samp{pointer}
or @samp{__pointer__} for the mode used to represent pointers.
-@item nocommon
-@cindex @code{nocommon} attribute
-@opindex fno-common
-This attribute specifies requests GCC not to place a variable
-``common'' but instead to allocate space for it directly. If you
-specify the @option{-fno-common} flag, GCC will do this for all
-variables.
-
-Specifying the @code{nocommon} attribute for a variable provides an
-initialization of zeros. A variable may only be initialized in one
-source file.
-
@item packed
@cindex @code{packed} attribute
The @code{packed} attribute specifies that a variable or structure field
The @code{shared} attribute is only available on Windows NT@.
+@item tls_model ("@var{tls_model}")
+@cindex @code{tls_model} attribute
+The @code{tls_model} attribute sets thread-local storage model
+(@pxref{Thread-Local}) of a particular @code{__thread} variable,
+overriding @code{-ftls-model=} command line switch on a per-variable
+basis.
+The @var{tls_model} argument should be one of @code{global-dynamic},
+@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
+
+Not all targets support this attribute.
+
@item transparent_union
This attribute, attached to a function parameter which is a union, means
that the corresponding argument may have the type of any union member,
to be possibly unused. GCC will not produce a warning for this
variable.
-@item deprecated
-The @code{deprecated} attribute results in a warning if the variable
-is used anywhere in the source file. This is useful when identifying
-variables that are expected to be removed in a future version of a
-program. The warning also includes the location of the declaration
-of the deprecated variable, to enable users to easily find further
-information about why the variable is deprecated, or what they should
-do instead. Note that the warnings only occurs for uses:
-
-@smallexample
-extern int old_var __attribute__ ((deprecated));
-extern int old_var;
-int new_fn () @{ return old_var; @}
-@end smallexample
-
-results in a warning on line 3 but not line 2.
-
-The @code{deprecated} attribute can also be used for functions and
-types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
-
@item vector_size (@var{bytes})
This attribute specifies the vector size for the variable, measured in
bytes. For example, the declaration:
@item weak
The @code{weak} attribute is described in @xref{Function Attributes}.
+@end table
+
+@subsection M32R/D Variable Attributes
+
+One attribute is currently defined for the M32R/D.
+@table @code
@item model (@var{model-name})
@cindex variable addressability on the M32R/D
Use this attribute on the M32R/D to set the addressability of an object.
Medium and large model objects may live anywhere in the 32-bit address space
(the compiler will generate @code{seth/add3} instructions to load their
addresses).
+@end table
@subsection i386 Variable Attributes
Two attributes are currently defined for i386 configurations:
@code{ms_struct} and @code{gcc_struct}
+@table @code
@item ms_struct
@itemx gcc_struct
-@cindex @code{ms_struct}
-@cindex @code{gcc_struct}
+@cindex @code{ms_struct} attribute
+@cindex @code{gcc_struct} attribute
If @code{packed} is used on a structure, or if bit-fields are used
it may be that the Microsoft ABI packs them differently
Currently @option{-m[no-]ms-bitfields} is provided for the Windows X86
compilers to match the native Microsoft compiler.
-
@end table
-To specify multiple attributes, separate them by commas within the
-double parentheses: for example, @samp{__attribute__ ((aligned (16),
-packed))}.
-
@node Type Attributes
@section Specifying Attributes of Types
@cindex attribute of types
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