diff options
| -rw-r--r-- | ChangeLog | 14 | ||||
| -rw-r--r-- | manual/memory.texi | 61 |
2 files changed, 58 insertions, 17 deletions
@@ -1,3 +1,17 @@ +2013-12-16 Will Newton <will.newton@linaro.org> + + * manual/memory.texi (Malloc Examples): Clarify default + alignment documentation. Suggest posix_memalign rather + than memalign or valloc. + (Aligned Memory Blocks): Remove suggestion to use memalign + or valloc. Remove obsolete comment about BSD. + Document memalign errno values and mark the function obsolete. + Document posix_memalign returned error codes. Mark valloc + as obsolete. (Hooks for Malloc): __memalign_hook is also + called for posix_memalign and valloc. + (Summary of Malloc): Add posix_memalign to function summary. + __memalign_hook is also called for posix_memalign and valloc. + 2013-12-16 Siddhesh Poyarekar <siddhesh@redhat.com> * sysdeps/ieee754/dbl-64/s_sin.c (TAYLOR_SINCOS): Rename to diff --git a/manual/memory.texi b/manual/memory.texi index a80f87c..3d96f35 100644 --- a/manual/memory.texi +++ b/manual/memory.texi @@ -380,10 +380,10 @@ savestring (const char *ptr, size_t len) 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 most systems, and a multiple of 16 on +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{memalign}, -@code{posix_memalign} or @code{valloc} (@pxref{Aligned Memory Blocks}). +boundary) necessary; for those cases, use @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 @@ -616,14 +616,8 @@ 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{memalign}, @code{posix_memalign}, or -@code{valloc}. @code{memalign} is declared in @file{malloc.h} and -@code{posix_memalign} is declared in @file{stdlib.h}. - -With @theglibc{}, you can use @code{free} to free the blocks that -@code{memalign}, @code{posix_memalign}, and @code{valloc} return. That -does not work in BSD, however---BSD does not provide any way to free -such blocks. +power of two than that, use @code{posix_memalign}. @code{posix_memalign} +is declared in @file{stdlib.h}. @comment malloc.h @comment BSD @@ -633,6 +627,21 @@ address is a multiple of @var{boundary}. The @var{boundary} must be a power of two! The function @code{memalign} works by allocating a somewhat larger block, and then returning an address within the block that is on the specified boundary. + +The @code{memalign} 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. + +@end table + +The @code{memalign} function is obsolete and @code{posix_memalign} should +be used instead. @end deftypefun @comment stdlib.h @@ -647,6 +656,16 @@ parameter @var{alignment}: the value must be a power of two multiple of If the function succeeds in allocation memory a pointer to the allocated memory is returned in @code{*@var{memptr}} and the return value is zero. Otherwise the function returns an error value indicating the problem. +The possible error values returned are: + +@table @code +@item ENOMEM +There was insufficient memory available to satisfy the request. + +@item EINVAL +@var{alignment} is not a power of two multiple of @code{sizeof (void *)}. + +@end table This function was introduced in POSIX 1003.1d. @end deftypefun @@ -667,6 +686,9 @@ 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. @end deftypefun @node Malloc Tunable Parameters @@ -902,17 +924,17 @@ 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} -uses whenever it is 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{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: @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} function was called. This value allows you to trace the -memory consumption of the program. +the @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 @@ -1118,6 +1140,10 @@ Space}. Allocate a block of @var{size} bytes, starting on a page boundary. @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}. + @item void *memalign (size_t @var{size}, size_t @var{boundary}) Allocate a block of @var{size} bytes, starting on an address that is a multiple of @var{boundary}. @xref{Aligned Memory Blocks}. @@ -1140,7 +1166,8 @@ 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} uses whenever it is called. +A pointer to a function that @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. |