Originální popis anglicky:
alloca - memory allocator
Návod, kniha: Linux Programmer's Manual
#include <alloca.h>
void *alloca(size_t size);
The
alloca function allocates
size bytes of space in the stack
frame of the caller. This temporary space is automatically freed when the
function that called
alloca returns to its caller.
The
alloca function returns a pointer to the beginning of the allocated
space. If the allocation causes stack overflow, program behaviour is
undefined.
There is evidence that the
alloca function appeared in 32v, pwb, pwb.2,
3bsd, and 4bsd. There is a man page for it in BSD 4.3. Linux uses the GNU
version. This function is not in POSIX or SUSv3.
Normally,
gcc translates calls to
alloca by inlined code. This is
not done when either the -ansi or the -fno-builtin option is given. But
beware! By default the glibc version of
<stdlib.h> includes
<alloca.h> and that contains the line
# define alloca(size) __builtin_alloca
(size)
with messy consequences if one has a private version of this function.
The fact that the code is inlined, means that it is impossible to take the
address of this function, or to change its behaviour by linking with a
different library.
The inlined code often consists of a single instruction adjusting the stack
pointer, and does not check for stack overflow. Thus, there is no NULL error
return.
The
alloca function is machine and compiler dependent. On many systems
its implementation is buggy. Its use is discouraged.
On many systems
alloca cannot be used inside the list of arguments of a
function call, because the stack space reserved by
alloca would appear
on the stack in the middle of the space for the function arguments.
brk(2),
pagesize(2),
calloc(3),
malloc(3),
realloc(3)
