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re PR c/3504 (__alignof__ not working correctly)

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PR c/3504
	* doc/extend.texi: Correct documentation of __alignof__.

From-SVN: r49126
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Neil Booth 2002-01-23 07:51:16 +00:00 committed by Neil Booth
parent 9b6e0e57a1
commit 5372b3fbe8
2 changed files with 12 additions and 12 deletions
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gcc/ChangeLog
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@ -1,3 +1,8 @@
2002-01-23 Neil Booth <neil@daikokuya.demon.co.uk>
PR c/3504
* doc/extend.texi: Correct documentation of __alignof__.
2002-01-22 Zack Weinberg <zack@codesourcery.com>
* params.h: Rename arguments of DEFPARAM so that it will be

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gcc/doc/extend.texi
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@ -2754,27 +2754,22 @@ Some machines never actually require alignment; they allow reference to any
data type even at an odd addresses. For these machines, @code{__alignof__}
reports the @emph{recommended} alignment of a type.
When the operand of @code{__alignof__} is an lvalue rather than a type, the
value is the largest alignment that the lvalue is known to have. It may
have this alignment as a result of its data type, or because it is part of
a structure and inherits alignment from that structure. For example, after
this declaration:
If the operand of @code{__alignof__} is an lvalue rather than a type,
its value is the required alignment for its type, taking into account
any minimum alignment specified with GCC's @code{__attribute__}
extension (@pxref{Variable Attributes}). For example, after this
declaration:
@example
struct foo @{ int x; char y; @} foo1;
@end example
@noindent
the value of @code{__alignof__ (foo1.y)} is probably 2 or 4, the same as
@code{__alignof__ (int)}, even though the data type of @code{foo1.y}
does not itself demand any alignment.
the value of @code{__alignof__ (foo1.y)} is 1, even though its actual
alignment is probably 2 or 4, the same as @code{__alignof__ (int)}.
It is an error to ask for the alignment of an incomplete type.
A related feature which lets you specify the alignment of an object is
@code{__attribute__ ((aligned (@var{alignment})))}; see the following
section.
@node Variable Attributes
@section Specifying Attributes of Variables
@cindex attribute of variables