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@node Obstacks,Licenses,Functions,Top

@chapter Obstacks

@cindex obstacks

An @dfn{obstack} is a pool of memory containing a stack of objects.  You

can create any number of separate obstacks, and then allocate objects in

specified obstacks.  Within each obstack, the last object allocated must

always be the first one freed, but distinct obstacks are independent of

each other.

Aside from this one constraint of order of freeing, obstacks are totally

general: an obstack can contain any number of objects of any size.  They

are implemented with macros, so allocation is usually very fast as long as

the objects are usually small.  And the only space overhead per object is

the padding needed to start each object on a suitable boundary.

@menu

* Creating Obstacks::           How to declare an obstack in your program.

* Preparing for Obstacks::      Preparations needed before you can

                                 use obstacks.

* Allocation in an Obstack::    Allocating objects in an obstack.

* Freeing Obstack Objects::     Freeing objects in an obstack.

* Obstack Functions::           The obstack functions are both

                                 functions and macros.

* Growing Objects::             Making an object bigger by stages.

* Extra Fast Growing::          Extra-high-efficiency (though more

                                 complicated) growing objects.

* Status of an Obstack::        Inquiries about the status of an obstack.

* Obstacks Data Alignment::     Controlling alignment of objects in obstacks.

* Obstack Chunks::              How obstacks obtain and release chunks;

                                 efficiency considerations.

* Summary of Obstacks::

@end menu

@node Creating Obstacks

@section Creating Obstacks

The utilities for manipulating obstacks are declared in the header

file @file{obstack.h}.

@pindex obstack.h

@comment obstack.h

@comment GNU

@deftp {Data Type} {struct obstack}

An obstack is represented by a data structure of type @code{struct

obstack}.  This structure has a small fixed size; it records the status

of the obstack and how to find the space in which objects are allocated.

It does not contain any of the objects themselves.  You should not try

to access the contents of the structure directly; use only the functions

described in this chapter.

@end deftp

You can declare variables of type @code{struct obstack} and use them as

obstacks, or you can allocate obstacks dynamically like any other kind

of object.  Dynamic allocation of obstacks allows your program to have a

variable number of different stacks.  (You can even allocate an

obstack structure in another obstack, but this is rarely useful.)

All the functions that work with obstacks require you to specify which

obstack to use.  You do this with a pointer of type @code{struct obstack

*}.  In the following, we often say ``an obstack'' when strictly

speaking the object at hand is such a pointer.

The objects in the obstack are packed into large blocks called

@dfn{chunks}.  The @code{struct obstack} structure points to a chain of

the chunks currently in use.

The obstack library obtains a new chunk whenever you allocate an object

that won't fit in the previous chunk.  Since the obstack library manages

chunks automatically, you don't need to pay much attention to them, but

you do need to supply a function which the obstack library should use to

get a chunk.  Usually you supply a function which uses @code{malloc}

directly or indirectly.  You must also supply a function to free a chunk.

These matters are described in the following section.

@node Preparing for Obstacks

@section Preparing for Using Obstacks

Each source file in which you plan to use the obstack functions

must include the header file @file{obstack.h}, like this:

@smallexample

#include <obstack.h>

@end smallexample

@findex obstack_chunk_alloc

@findex obstack_chunk_free

Also, if the source file uses the macro @code{obstack_init}, it must

declare or define two functions or macros that will be called by the

obstack library.  One, @code{obstack_chunk_alloc}, is used to allocate

the chunks of memory into which objects are packed.  The other,

@code{obstack_chunk_free}, is used to return chunks when the objects in

them are freed.  These macros should appear before any use of obstacks

in the source file.

Usually these are defined to use @code{malloc} via the intermediary

@code{xmalloc} (@pxref{Unconstrained Allocation, , , libc, The GNU C Library Reference Manual}).  This is done with

the following pair of macro definitions:

@smallexample

#define obstack_chunk_alloc xmalloc

#define obstack_chunk_free free

@end smallexample

@noindent

Though the memory you get using obstacks really comes from @code{malloc},

using obstacks is faster because @code{malloc} is called less often, for

larger blocks of memory.  @xref{Obstack Chunks}, for full details.

At run time, before the program can use a @code{struct obstack} object

as an obstack, it must initialize the obstack by calling

@code{obstack_init}.

@comment obstack.h

@comment GNU

@deftypefun int obstack_init (struct obstack *@var{obstack-ptr})

Initialize obstack @var{obstack-ptr} for allocation of objects.  This

function calls the obstack's @code{obstack_chunk_alloc} function.  If

allocation of memory fails, the function pointed to by

@code{obstack_alloc_failed_handler} is called.  The @code{obstack_init}

function always returns 1 (Compatibility notice: Former versions of

obstack returned 0 if allocation failed).

@end deftypefun

Here are two examples of how to allocate the space for an obstack and

initialize it.  First, an obstack that is a static variable:

@smallexample

static struct obstack myobstack;

@dots{}

obstack_init (&myobstack);

@end smallexample

@noindent

Second, an obstack that is itself dynamically allocated:

@smallexample

struct obstack *myobstack_ptr

  = (struct obstack *) xmalloc (sizeof (struct obstack));

obstack_init (myobstack_ptr);

@end smallexample

@comment obstack.h

@comment GNU

@defvar obstack_alloc_failed_handler

The value of this variable is a pointer to a function that

@code{obstack} uses when @code{obstack_chunk_alloc} fails to allocate

memory.  The default action is to print a message and abort.

You should supply a function that either calls @code{exit}

(@pxref{Program Termination, , , libc, The GNU C Library Reference Manual}) or @code{longjmp} (@pxref{Non-Local

Exits, , , libc, The GNU C Library Reference Manual}) and doesn't return.

@smallexample

void my_obstack_alloc_failed (void)

@dots{}

obstack_alloc_failed_handler = &my_obstack_alloc_failed;

@end smallexample

@end defvar

@node Allocation in an Obstack

@section Allocation in an Obstack

@cindex allocation (obstacks)

The most direct way to allocate an object in an obstack is with

@code{obstack_alloc}, which is invoked almost like @code{malloc}.

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_alloc (struct obstack *@var{obstack-ptr}, int @var{size})

This allocates an uninitialized block of @var{size} bytes in an obstack

and returns its address.  Here @var{obstack-ptr} specifies which obstack

to allocate the block in; it is the address of the @code{struct obstack}

object which represents the obstack.  Each obstack function or macro

requires you to specify an @var{obstack-ptr} as the first argument.

This function calls the obstack's @code{obstack_chunk_alloc} function if

it needs to allocate a new chunk of memory; it calls

@code{obstack_alloc_failed_handler} if allocation of memory by

@code{obstack_chunk_alloc} failed.

@end deftypefun

For example, here is a function that allocates a copy of a string @var{str}

in a specific obstack, which is in the variable @code{string_obstack}:

@smallexample

struct obstack string_obstack;

char *

copystring (char *string)

@{

  size_t len = strlen (string) + 1;

  char *s = (char *) obstack_alloc (&string_obstack, len);

  memcpy (s, string, len);

  return s;

@}

@end smallexample

To allocate a block with specified contents, use the function

@code{obstack_copy}, declared like this:

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

This allocates a block and initializes it by copying @var{size}

bytes of data starting at @var{address}.  It calls

@code{obstack_alloc_failed_handler} if allocation of memory by

@code{obstack_chunk_alloc} failed.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

Like @code{obstack_copy}, but appends an extra byte containing a null

character.  This extra byte is not counted in the argument @var{size}.

@end deftypefun

The @code{obstack_copy0} function is convenient for copying a sequence

of characters into an obstack as a null-terminated string.  Here is an

example of its use:

@smallexample

char *

obstack_savestring (char *addr, int size)

@{

  return obstack_copy0 (&myobstack, addr, size);

@}

@end smallexample

@noindent

Contrast this with the previous example of @code{savestring} using

@code{malloc} (@pxref{Basic Allocation, , , libc, The GNU C Library Reference Manual}).

@node Freeing Obstack Objects

@section Freeing Objects in an Obstack

@cindex freeing (obstacks)

To free an object allocated in an obstack, use the function

@code{obstack_free}.  Since the obstack is a stack of objects, freeing

one object automatically frees all other objects allocated more recently

in the same obstack.

@comment obstack.h

@comment GNU

@deftypefun void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})

If @var{object} is a null pointer, everything allocated in the obstack

is freed.  Otherwise, @var{object} must be the address of an object

allocated in the obstack.  Then @var{object} is freed, along with

everything allocated in @var{obstack} since @var{object}.

@end deftypefun

Note that if @var{object} is a null pointer, the result is an

uninitialized obstack.  To free all memory in an obstack but leave it

valid for further allocation, call @code{obstack_free} with the address

of the first object allocated on the obstack:

@smallexample

obstack_free (obstack_ptr, first_object_allocated_ptr);

@end smallexample

Recall that the objects in an obstack are grouped into chunks.  When all

the objects in a chunk become free, the obstack library automatically

frees the chunk (@pxref{Preparing for Obstacks}).  Then other

obstacks, or non-obstack allocation, can reuse the space of the chunk.

@node Obstack Functions

@section Obstack Functions and Macros

@cindex macros

The interfaces for using obstacks may be defined either as functions or

as macros, depending on the compiler.  The obstack facility works with

all C compilers, including both @w{ISO C} and traditional C, but there are

precautions you must take if you plan to use compilers other than GNU C.

If you are using an old-fashioned @w{non-ISO C} compiler, all the obstack

``functions'' are actually defined only as macros.  You can call these

macros like functions, but you cannot use them in any other way (for

example, you cannot take their address).

Calling the macros requires a special precaution: namely, the first

operand (the obstack pointer) may not contain any side effects, because

it may be computed more than once.  For example, if you write this:

@smallexample

obstack_alloc (get_obstack (), 4);

@end smallexample

@noindent

you will find that @code{get_obstack} may be called several times.

If you use @code{*obstack_list_ptr++} as the obstack pointer argument,

you will get very strange results since the incrementation may occur

several times.

In @w{ISO C}, each function has both a macro definition and a function

definition.  The function definition is used if you take the address of the

function without calling it.  An ordinary call uses the macro definition by

default, but you can request the function definition instead by writing the

function name in parentheses, as shown here:

@smallexample

char *x;

void *(*funcp) ();

/* @r{Use the macro}.  */

x = (char *) obstack_alloc (obptr, size);

/* @r{Call the function}.  */

x = (char *) (obstack_alloc) (obptr, size);

/* @r{Take the address of the function}.  */

funcp = obstack_alloc;

@end smallexample

@noindent

This is the same situation that exists in @w{ISO C} for the standard library

functions.  @xref{Macro Definitions, , , libc, The GNU C Library Reference Manual}.

@strong{Warning:} When you do use the macros, you must observe the

precaution of avoiding side effects in the first operand, even in @w{ISO C}.

If you use the GNU C compiler, this precaution is not necessary, because

various language extensions in GNU C permit defining the macros so as to

compute each argument only once.

@node Growing Objects

@section Growing Objects

@cindex growing objects (in obstacks)

@cindex changing the size of a block (obstacks)

Because memory in obstack chunks is used sequentially, it is possible to

build up an object step by step, adding one or more bytes at a time to the

end of the object.  With this technique, you do not need to know how much

data you will put in the object until you come to the end of it.  We call

this the technique of @dfn{growing objects}.  The special functions

for adding data to the growing object are described in this section.

You don't need to do anything special when you start to grow an object.

Using one of the functions to add data to the object automatically

starts it.  However, it is necessary to say explicitly when the object is

finished.  This is done with the function @code{obstack_finish}.

The actual address of the object thus built up is not known until the

object is finished.  Until then, it always remains possible that you will

add so much data that the object must be copied into a new chunk.

While the obstack is in use for a growing object, you cannot use it for

ordinary allocation of another object.  If you try to do so, the space

already added to the growing object will become part of the other object.

@comment obstack.h

@comment GNU

@deftypefun void obstack_blank (struct obstack *@var{obstack-ptr}, int @var{size})

The most basic function for adding to a growing object is

@code{obstack_blank}, which adds space without initializing it.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})

To add a block of initialized space, use @code{obstack_grow}, which is

the growing-object analogue of @code{obstack_copy}.  It adds @var{size}

bytes of data to the growing object, copying the contents from

@var{data}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})

This is the growing-object analogue of @code{obstack_copy0}.  It adds

@var{size} bytes copied from @var{data}, followed by an additional null

character.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{c})

To add one character at a time, use the function @code{obstack_1grow}.

It adds a single byte containing @var{c} to the growing object.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_ptr_grow (struct obstack *@var{obstack-ptr}, void *@var{data})

Adding the value of a pointer one can use the function

@code{obstack_ptr_grow}.  It adds @code{sizeof (void *)} bytes

containing the value of @var{data}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_int_grow (struct obstack *@var{obstack-ptr}, int @var{data})

A single value of type @code{int} can be added by using the

@code{obstack_int_grow} function.  It adds @code{sizeof (int)} bytes to

the growing object and initializes them with the value of @var{data}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_finish (struct obstack *@var{obstack-ptr})

When you are finished growing the object, use the function

@code{obstack_finish} to close it off and return its final address.

Once you have finished the object, the obstack is available for ordinary

allocation or for growing another object.

This function can return a null pointer under the same conditions as

@code{obstack_alloc} (@pxref{Allocation in an Obstack}).

@end deftypefun

When you build an object by growing it, you will probably need to know

afterward how long it became.  You need not keep track of this as you grow

the object, because you can find out the length from the obstack just

before finishing the object with the function @code{obstack_object_size},

declared as follows:

@comment obstack.h

@comment GNU

@deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})

This function returns the current size of the growing object, in bytes.

Remember to call this function @emph{before} finishing the object.

After it is finished, @code{obstack_object_size} will return zero.

@end deftypefun

If you have started growing an object and wish to cancel it, you should

finish it and then free it, like this:

@smallexample

obstack_free (obstack_ptr, obstack_finish (obstack_ptr));

@end smallexample

@noindent

This has no effect if no object was growing.

@cindex shrinking objects

You can use @code{obstack_blank} with a negative size argument to make

the current object smaller.  Just don't try to shrink it beyond zero

length---there's no telling what will happen if you do that.

@node Extra Fast Growing

@section Extra Fast Growing Objects

@cindex efficiency and obstacks

The usual functions for growing objects incur overhead for checking

whether there is room for the new growth in the current chunk.  If you

are frequently constructing objects in small steps of growth, this

overhead can be significant.

You can reduce the overhead by using special ``fast growth''

functions that grow the object without checking.  In order to have a

robust program, you must do the checking yourself.  If you do this checking

in the simplest way each time you are about to add data to the object, you

have not saved anything, because that is what the ordinary growth

functions do.  But if you can arrange to check less often, or check

more efficiently, then you make the program faster.

The function @code{obstack_room} returns the amount of room available

in the current chunk.  It is declared as follows:

@comment obstack.h

@comment GNU

@deftypefun int obstack_room (struct obstack *@var{obstack-ptr})

This returns the number of bytes that can be added safely to the current

growing object (or to an object about to be started) in obstack

@var{obstack} using the fast growth functions.

@end deftypefun

While you know there is room, you can use these fast growth functions

for adding data to a growing object:

@comment obstack.h

@comment GNU

@deftypefun void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{c})

The function @code{obstack_1grow_fast} adds one byte containing the

character @var{c} to the growing object in obstack @var{obstack-ptr}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_ptr_grow_fast (struct obstack *@var{obstack-ptr}, void *@var{data})

The function @code{obstack_ptr_grow_fast} adds @code{sizeof (void *)}

bytes containing the value of @var{data} to the growing object in

obstack @var{obstack-ptr}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_int_grow_fast (struct obstack *@var{obstack-ptr}, int @var{data})

The function @code{obstack_int_grow_fast} adds @code{sizeof (int)} bytes

containing the value of @var{data} to the growing object in obstack

@var{obstack-ptr}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun void obstack_blank_fast (struct obstack *@var{obstack-ptr}, int @var{size})

The function @code{obstack_blank_fast} adds @var{size} bytes to the

growing object in obstack @var{obstack-ptr} without initializing them.

@end deftypefun

When you check for space using @code{obstack_room} and there is not

enough room for what you want to add, the fast growth functions

are not safe.  In this case, simply use the corresponding ordinary

growth function instead.  Very soon this will copy the object to a

new chunk; then there will be lots of room available again.

So, each time you use an ordinary growth function, check afterward for

sufficient space using @code{obstack_room}.  Once the object is copied

to a new chunk, there will be plenty of space again, so the program will

start using the fast growth functions again.

Here is an example:

@smallexample

@group

void

add_string (struct obstack *obstack, const char *ptr, int len)

@{

  while (len > 0)

    @{

      int room = obstack_room (obstack);

      if (room == 0)

        @{

          /* @r{Not enough room. Add one character slowly,}

             @r{which may copy to a new chunk and make room.}  */

          obstack_1grow (obstack, *ptr++);

          len--;

        @}

      else

        @{

          if (room > len)

            room = len;

          /* @r{Add fast as much as we have room for.} */

          len -= room;

          while (room-- > 0)

            obstack_1grow_fast (obstack, *ptr++);

        @}

    @}

@}

@end group

@end smallexample

@node Status of an Obstack

@section Status of an Obstack

@cindex obstack status

@cindex status of obstack

Here are functions that provide information on the current status of

allocation in an obstack.  You can use them to learn about an object while

still growing it.

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_base (struct obstack *@var{obstack-ptr})

This function returns the tentative address of the beginning of the

currently growing object in @var{obstack-ptr}.  If you finish the object

immediately, it will have that address.  If you make it larger first, it

may outgrow the current chunk---then its address will change!

If no object is growing, this value says where the next object you

allocate will start (once again assuming it fits in the current

chunk).

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun {void *} obstack_next_free (struct obstack *@var{obstack-ptr})

This function returns the address of the first free byte in the current

chunk of obstack @var{obstack-ptr}.  This is the end of the currently

growing object.  If no object is growing, @code{obstack_next_free}

returns the same value as @code{obstack_base}.

@end deftypefun

@comment obstack.h

@comment GNU

@deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})

This function returns the size in bytes of the currently growing object.

This is equivalent to

@smallexample

obstack_next_free (@var{obstack-ptr}) - obstack_base (@var{obstack-ptr})

@end smallexample

@end deftypefun

@node Obstacks Data Alignment

@section Alignment of Data in Obstacks

@cindex alignment (in obstacks)

Each obstack has an @dfn{alignment boundary}; each object allocated in

the obstack automatically starts on an address that is a multiple of the

specified boundary.  By default, this boundary is 4 bytes.

To access an obstack's alignment boundary, use the macro

@code{obstack_alignment_mask}, whose function prototype looks like

this:

@comment obstack.h

@comment GNU

@deftypefn Macro int obstack_alignment_mask (struct obstack *@var{obstack-ptr})

The value is a bit mask; a bit that is 1 indicates that the corresponding

bit in the address of an object should be 0.  The mask value should be one

less than a power of 2; the effect is that all object addresses are

multiples of that power of 2.  The default value of the mask is 3, so that

addresses are multiples of 4.  A mask value of 0 means an object can start

on any multiple of 1 (that is, no alignment is required).

The expansion of the macro @code{obstack_alignment_mask} is an lvalue,

so you can alter the mask by assignment.  For example, this statement:

@smallexample

obstack_alignment_mask (obstack_ptr) = 0;

@end smallexample

@noindent

has the effect of turning off alignment processing in the specified obstack.

@end deftypefn

Note that a change in alignment mask does not take effect until

@emph{after} the next time an object is allocated or finished in the

obstack.  If you are not growing an object, you can make the new

alignment mask take effect immediately by calling @code{obstack_finish}.

This will finish a zero-length object and then do proper alignment for

the next object.

@node Obstack Chunks

@section Obstack Chunks

@cindex efficiency of chunks

@cindex chunks

Obstacks work by allocating space for themselves in large chunks, and

then parceling out space in the chunks to satisfy your requests.  Chunks

are normally 4096 bytes long unless you specify a different chunk size.

The chunk size includes 8 bytes of overhead that are not actually used

for storing objects.  Regardless of the specified size, longer chunks

will be allocated when necessary for long objects.

The obstack library allocates chunks by calling the function

@code{obstack_chunk_alloc}, which you must define.  When a chunk is no

longer needed because you have freed all the objects in it, the obstack

library frees the chunk by calling @code{obstack_chunk_free}, which you

must also define.

These two must be defined (as macros) or declared (as functions) in each

source file that uses @code{obstack_init} (@pxref{Creating Obstacks}).

Most often they are defined as macros like this:

@smallexample

#define obstack_chunk_alloc malloc

#define obstack_chunk_free free

@end smallexample

Note that these are simple macros (no arguments).  Macro definitions with

arguments will not work!  It is necessary that @code{obstack_chunk_alloc}

or @code{obstack_chunk_free}, alone, expand into a function name if it is

not itself a function name.

If you allocate chunks with @code{malloc}, the chunk size should be a

power of 2.  The default chunk size, 4096, was chosen because it is long

enough to satisfy many typical requests on the obstack yet short enough

not to waste too much memory in the portion of the last chunk not yet used.

@comment obstack.h

@comment GNU

@deftypefn Macro int obstack_chunk_size (struct obstack *@var{obstack-ptr})

This returns the chunk size of the given obstack.

@end deftypefn

Since this macro expands to an lvalue, you can specify a new chunk size by

assigning it a new value.  Doing so does not affect the chunks already

allocated, but will change the size of chunks allocated for that particular

obstack in the future.  It is unlikely to be useful to make the chunk size

smaller, but making it larger might improve efficiency if you are

allocating many objects whose size is comparable to the chunk size.  Here

is how to do so cleanly:

@smallexample

if (obstack_chunk_size (obstack_ptr) < @var{new-chunk-size})

  obstack_chunk_size (obstack_ptr) = @var{new-chunk-size};

@end smallexample

@node Summary of Obstacks

@section Summary of Obstack Functions

Here is a summary of all the functions associated with obstacks.  Each

takes the address of an obstack (@code{struct obstack *}) as its first

argument.

@table @code

@item void obstack_init (struct obstack *@var{obstack-ptr})

Initialize use of an obstack.  @xref{Creating Obstacks}.

@item void *obstack_alloc (struct obstack *@var{obstack-ptr}, int @var{size})

Allocate an object of @var{size} uninitialized bytes.

@xref{Allocation in an Obstack}.

@item void *obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

Allocate an object of @var{size} bytes, with contents copied from

@var{address}.  @xref{Allocation in an Obstack}.

@item void *obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

Allocate an object of @var{size}+1 bytes, with @var{size} of them copied

from @var{address}, followed by a null character at the end.

@xref{Allocation in an Obstack}.

@item void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})

Free @var{object} (and everything allocated in the specified obstack

more recently than @var{object}).  @xref{Freeing Obstack Objects}.

@item void obstack_blank (struct obstack *@var{obstack-ptr}, int @var{size})

Add @var{size} uninitialized bytes to a growing object.

@xref{Growing Objects}.

@item void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

Add @var{size} bytes, copied from @var{address}, to a growing object.

@xref{Growing Objects}.

@item void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})

Add @var{size} bytes, copied from @var{address}, to a growing object,

and then add another byte containing a null character.  @xref{Growing

Objects}.

@item void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{data-char})

Add one byte containing @var{data-char} to a growing object.

@xref{Growing Objects}.

@item void *obstack_finish (struct obstack *@var{obstack-ptr})

Finalize the object that is growing and return its permanent address.

@xref{Growing Objects}.

@item int obstack_object_size (struct obstack *@var{obstack-ptr})

Get the current size of the currently growing object.  @xref{Growing

Objects}.

@item void obstack_blank_fast (struct obstack *@var{obstack-ptr}, int @var{size})

Add @var{size} uninitialized bytes to a growing object without checking

that there is enough room.  @xref{Extra Fast Growing}.

@item void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{data-char})

Add one byte containing @var{data-char} to a growing object without

checking that there is enough room.  @xref{Extra Fast Growing}.

@item int obstack_room (struct obstack *@var{obstack-ptr})

Get the amount of room now available for growing the current object.

@xref{Extra Fast Growing}.

@item int obstack_alignment_mask (struct obstack *@var{obstack-ptr})

The mask used for aligning the beginning of an object.  This is an

lvalue.  @xref{Obstacks Data Alignment}.

@item int obstack_chunk_size (struct obstack *@var{obstack-ptr})

The size for allocating chunks.  This is an lvalue.  @xref{Obstack Chunks}.

@item void *obstack_base (struct obstack *@var{obstack-ptr})

Tentative starting address of the currently growing object.

@xref{Status of an Obstack}.

@item void *obstack_next_free (struct obstack *@var{obstack-ptr})

Address just after the end of the currently growing object.

@xref{Status of an Obstack}.

@end table