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Reduce discussion of types to which size_t may be equivalent.

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Joseph Myers 2012-03-05 15:03:57 +00:00
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commit ed58a00f9b
2 changed files with 8 additions and 16 deletions
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ChangeLog
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@ -1,3 +1,9 @@
2012-03-05 Joseph Myers <joseph@codesourcery.com>
* manual/lang.texi (size_t): Note types to which size_t may be
equivalent with the GNU C Library, but do not describe when
differences between them are significant.
2012-03-05 Andreas Jaeger <aj@suse.de>
* sysdeps/i386/fpu/libm-test-ulps: Update.

18
manual/lang.texi
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@ -629,27 +629,13 @@ This is an unsigned integer type used to represent the sizes of objects.
The result of the @code{sizeof} operator is of this type, and functions
such as @code{malloc} (@pxref{Unconstrained Allocation}) and
@code{memcpy} (@pxref{Copying and Concatenation}) accept arguments of
this type to specify object sizes.
this type to specify object sizes. On systems using @theglibc{}, this
will be @w{@code{unsigned int}} or @w{@code{unsigned long int}}.
@strong{Usage Note:} @code{size_t} is the preferred way to declare any
arguments or variables that hold the size of an object.
@end deftp
In the GNU system @code{size_t} is equivalent to either
@w{@code{unsigned int}} or @w{@code{unsigned long int}}. These types
have identical properties on the GNU system and, for most purposes, you
can use them interchangeably. However, they are distinct as data types,
which makes a difference in certain contexts.
For example, when you specify the type of a function argument in a
function prototype, it makes a difference which one you use. If the
system header files declare @code{malloc} with an argument of type
@code{size_t} and you declare @code{malloc} with an argument of type
@code{unsigned int}, you will get a compilation error if @code{size_t}
happens to be @code{unsigned long int} on your system. To avoid any
possibility of error, when a function argument or value is supposed to
have type @code{size_t}, never declare its type in any other way.
@strong{Compatibility Note:} Implementations of C before the advent of
@w{ISO C} generally used @code{unsigned int} for representing object sizes
and @code{int} for pointer subtraction results. They did not