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manual/memory.texi: Document aligned_alloc.

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ChangeLog:

2013-12-16  Will Newton  <will.newton@linaro.org>

	* manual/memory.texi (Malloc Examples): Mention aligned_alloc.
	(Aligned Memory Blocks): Add documentation for aligned_alloc
	and suggest it as an alternative to posix_memalign.
	(Hooks for Malloc): Document __memalign_hook is also called
	for aligned_alloc.  (Summary of Malloc): Add summary for
	aligned alloc.  Document __memalign_hook is also called
	for aligned_alloc.
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Will Newton 2013-11-06 16:07:25 +00:00
parent 0a096e4487
commit 5764c27f8b
2 changed files with 57 additions and 16 deletions
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ChangeLog
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@ -1,3 +1,13 @@
2013-12-16 Will Newton <will.newton@linaro.org>
* manual/memory.texi (Malloc Examples): Mention aligned_alloc.
(Aligned Memory Blocks): Add documentation for aligned_alloc
and suggest it as an alternative to posix_memalign.
(Hooks for Malloc): Document __memalign_hook is also called
for aligned_alloc. (Summary of Malloc): Add summary for
aligned alloc. Document __memalign_hook is also called
for aligned_alloc.
2013-12-16 Will Newton <will.newton@linaro.org>
* manual/memory.texi (Malloc Examples): Clarify default

63
manual/memory.texi
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@ -382,8 +382,8 @@ The block that @code{malloc} gives you is guaranteed to be aligned so
that it can hold any type of data. On @gnusystems{}, the address is
always a multiple of eight on 32-bit systems, and a multiple of 16 on
64-bit systems. Only rarely is any higher boundary (such as a page
boundary) necessary; for those cases, use @code{posix_memalign}
(@pxref{Aligned Memory Blocks}).
boundary) necessary; for those cases, use @code{aligned_alloc} or
@code{posix_memalign} (@pxref{Aligned Memory Blocks}).
Note that the memory located after the end of the block is likely to be
in use for something else; perhaps a block already allocated by another
@ -616,8 +616,31 @@ after calling @code{free} wastes memory. The size threshold for
The address of a block returned by @code{malloc} or @code{realloc} in
@gnusystems{} is always a multiple of eight (or sixteen on 64-bit
systems). If you need a block whose address is a multiple of a higher
power of two than that, use @code{posix_memalign}. @code{posix_memalign}
is declared in @file{stdlib.h}.
power of two than that, use @code{aligned_alloc} or @code{posix_memalign}.
@code{aligned_alloc} and @code{posix_memalign} are declared in
@file{stdlib.h}.
@comment stdlib.h
@deftypefun {void *} aligned_alloc (size_t @var{alignment}, size_t @var{size})
The @code{aligned_alloc} function allocates a block of @var{size} bytes whose
address is a multiple of @var{alignment}. The @var{alignment} must be a
power of two and @var{size} must be a multiple of @var{alignment}.
The @code{aligned_alloc} function returns a null pointer on error and sets
@code{errno} to one of the following values:
@table @code
@item ENOMEM
There was insufficient memory available to satisfy the request.
@item EINVAL
@var{alignment} is not a power of two.
This function was introduced in @w{ISO C11} and hence may have better
portability to modern non-POSIX systems than @code{posix_memalign}.
@end table
@end deftypefun
@comment malloc.h
@comment BSD
@ -640,8 +663,8 @@ There was insufficient memory available to satisfy the request.
@end table
The @code{memalign} function is obsolete and @code{posix_memalign} should
be used instead.
The @code{memalign} function is obsolete and @code{aligned_alloc} or
@code{posix_memalign} should be used instead.
@end deftypefun
@comment stdlib.h
@ -667,7 +690,9 @@ There was insufficient memory available to satisfy the request.
@end table
This function was introduced in POSIX 1003.1d.
This function was introduced in POSIX 1003.1d. Although this function is
superseded by @code{aligned_alloc}, it is more portable to older POSIX
systems that do not support @w{ISO C11}.
@end deftypefun
@comment malloc.h stdlib.h
@ -687,8 +712,8 @@ valloc (size_t size)
@ref{Query Memory Parameters} for more information about the memory
subsystem.
The @code{valloc} function is obsolete and @code{posix_memalign} should
be used instead.
The @code{valloc} function is obsolete and @code{aligned_alloc} or
@code{posix_memalign} should be used instead.
@end deftypefun
@node Malloc Tunable Parameters
@ -924,17 +949,19 @@ memory consumption of the program.
@comment malloc.h
@comment GNU
@defvar __memalign_hook
The value of this variable is a pointer to function that @code{memalign},
@code{posix_memalign} and @code{valloc} use whenever they are called.
You should define this function to look like @code{memalign}; that is, like:
The value of this variable is a pointer to function that @code{aligned_alloc},
@code{memalign}, @code{posix_memalign} and @code{valloc} use whenever they
are called. You should define this function to look like @code{aligned_alloc};
that is, like:
@smallexample
void *@var{function} (size_t @var{alignment}, size_t @var{size}, const void *@var{caller})
@end smallexample
The value of @var{caller} is the return address found on the stack when
the @code{memalign}, @code{posix_memalign} or @code{valloc} functions are
called. This value allows you to trace the memory consumption of the program.
the @code{aligned_alloc}, @code{memalign}, @code{posix_memalign} or
@code{valloc} functions are called. This value allows you to trace the
memory consumption of the program.
@end defvar
You must make sure that the function you install as a hook for one of
@ -1140,6 +1167,10 @@ Space}.
Allocate a block of @var{size} bytes, starting on a page boundary.
@xref{Aligned Memory Blocks}.
@item void *aligned_alloc (size_t @var{size}, size_t @var{alignment})
Allocate a block of @var{size} bytes, starting on an address that is a
multiple of @var{alignment}. @xref{Aligned Memory Blocks}.
@item int posix_memalign (void **@var{memptr}, size_t @var{alignment}, size_t @var{size})
Allocate a block of @var{size} bytes, starting on an address that is a
multiple of @var{alignment}. @xref{Aligned Memory Blocks}.
@ -1166,8 +1197,8 @@ A pointer to a function that @code{realloc} uses whenever it is called.
A pointer to a function that @code{free} uses whenever it is called.
@item void (*__memalign_hook) (size_t @var{size}, size_t @var{alignment}, const void *@var{caller})
A pointer to a function that @code{memalign}, @code{posix_memalign} and
@code{valloc} use whenever they are called.
A pointer to a function that @code{aligned_alloc}, @code{memalign},
@code{posix_memalign} and @code{valloc} use whenever they are called.
@item struct mallinfo mallinfo (void)
Return information about the current dynamic memory usage.