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1/* obstack.h - object stack macros
2 Copyright (C) 1988-2025 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/* Summary:
20
21 All the apparent functions defined here are macros. The idea
22 is that you would use these pre-tested macros to solve a
23 very specific set of problems, and they would run fast.
24 Caution: no side-effects in arguments please!! They may be
25 evaluated MANY times!!
26
27 These macros operate a stack of objects. Each object starts life
28 small, and may grow to maturity. (Consider building a word syllable
29 by syllable.) An object can move while it is growing. Once it has
30 been "finished" it never changes address again. So the "top of the
31 stack" is typically an immature growing object, while the rest of the
32 stack is of mature, fixed size and fixed address objects.
33
34 These routines grab large chunks of memory, using a function you
35 supply, called 'obstack_chunk_alloc'. On occasion, they free chunks,
36 by calling 'obstack_chunk_free'. You must define them and declare
37 them before using any obstack macros.
38
39 Each independent stack is represented by a 'struct obstack'.
40 Each of the obstack macros expects a pointer to such a structure
41 as the first argument.
42
43 One motivation for this package is the problem of growing char strings
44 in symbol tables. Unless you are "fascist pig with a read-only mind"
45 --Gosper's immortal quote from HAKMEM item 154, out of context--you
46 would not like to put any arbitrary upper limit on the length of your
47 symbols.
48
49 In practice this often means you will build many short symbols and a
50 few long symbols. At the time you are reading a symbol you don't know
51 how long it is. One traditional method is to read a symbol into a
52 buffer, realloc()ating the buffer every time you try to read a symbol
53 that is longer than the buffer. This is beaut, but you still will
54 want to copy the symbol from the buffer to a more permanent
55 symbol-table entry say about half the time.
56
57 With obstacks, you can work differently. Use one obstack for all symbol
58 names. As you read a symbol, grow the name in the obstack gradually.
59 When the name is complete, finalize it. Then, if the symbol exists already,
60 free the newly read name.
61
62 The way we do this is to take a large chunk, allocating memory from
63 low addresses. When you want to build a symbol in the chunk you just
64 add chars above the current "high water mark" in the chunk. When you
65 have finished adding chars, because you got to the end of the symbol,
66 you know how long the chars are, and you can create a new object.
67 Mostly the chars will not burst over the highest address of the chunk,
68 because you would typically expect a chunk to be (say) 100 times as
69 long as an average object.
70
71 In case that isn't clear, when we have enough chars to make up
72 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
73 so we just point to it where it lies. No moving of chars is
74 needed and this is the second win: potentially long strings need
75 never be explicitly shuffled. Once an object is formed, it does not
76 change its address during its lifetime.
77
78 When the chars burst over a chunk boundary, we allocate a larger
79 chunk, and then copy the partly formed object from the end of the old
80 chunk to the beginning of the new larger chunk. We then carry on
81 accreting characters to the end of the object as we normally would.
82
83 A special macro is provided to add a single char at a time to a
84 growing object. This allows the use of register variables, which
85 break the ordinary 'growth' macro.
86
87 Summary:
88 We allocate large chunks.
89 We carve out one object at a time from the current chunk.
90 Once carved, an object never moves.
91 We are free to append data of any size to the currently
92 growing object.
93 Exactly one object is growing in an obstack at any one time.
94 You can run one obstack per control block.
95 You may have as many control blocks as you dare.
96 Because of the way we do it, you can "unwind" an obstack
97 back to a previous state. (You may remove objects much
98 as you would with a stack.)
99 */
100
101
102/* Don't do the contents of this file more than once. */
103
104#ifndef _OBSTACK_H
105#define _OBSTACK_H 1
106
107/* We need the type of a pointer subtraction. If __PTRDIFF_TYPE__ is
108 defined, as with GNU C, use that; that way we don't pollute the
109 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h>
110 and use ptrdiff_t. */
111
112#ifdef __PTRDIFF_TYPE__
113# define PTR_INT_TYPE __PTRDIFF_TYPE__
114#else
115# include <stddef.h>
116# define PTR_INT_TYPE ptrdiff_t
117#endif
118
119/* If B is the base of an object addressed by P, return the result of
120 aligning P to the next multiple of A + 1. B and P must be of type
121 char *. A + 1 must be a power of 2. */
122
123#define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
124
125/* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case
126 where pointers can be converted to integers, aligned as integers,
127 and converted back again. If PTR_INT_TYPE is narrower than a
128 pointer (e.g., the AS/400), play it safe and compute the alignment
129 relative to B. Otherwise, use the faster strategy of computing the
130 alignment relative to 0. */
131
132#define __PTR_ALIGN(B, P, A) \
133 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
134 P, A)
135
136#include <string.h>
137
138#ifndef __attribute_pure__
139# define __attribute_pure__ _GL_ATTRIBUTE_PURE
140#endif
141
142#ifdef __cplusplus
143extern "C" {
144#endif
145
146struct _obstack_chunk /* Lives at front of each chunk. */
147{
148 char *limit; /* 1 past end of this chunk */
149 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
150 char contents[4]; /* objects begin here */
151};
152
153struct obstack /* control current object in current chunk */
154{
155 long chunk_size; /* preferred size to allocate chunks in */
156 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
157 char *object_base; /* address of object we are building */
158 char *next_free; /* where to add next char to current object */
159 char *chunk_limit; /* address of char after current chunk */
160 union
161 {
162 PTR_INT_TYPE tempint;
163 void *tempptr;
164 } temp; /* Temporary for some macros. */
165 int alignment_mask; /* Mask of alignment for each object. */
166 /* These prototypes vary based on 'use_extra_arg', and we use
167 casts to the prototypeless function type in all assignments,
168 but having prototypes here quiets -Wstrict-prototypes. */
169 struct _obstack_chunk *(*chunkfun) (void *, long);
170 void (*freefun) (void *, struct _obstack_chunk *);
171 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
172 unsigned use_extra_arg : 1; /* chunk alloc/dealloc funcs take extra arg */
173 unsigned maybe_empty_object : 1; /* There is a possibility that the current
174 chunk contains a zero-length object. This
175 prevents freeing the chunk if we allocate
176 a bigger chunk to replace it. */
177 unsigned alloc_failed : 1; /* No longer used, as we now call the failed
178 handler on error, but retained for binary
179 compatibility. */
180};
181
182/* Declare the external functions we use; they are in obstack.c. */
183
184extern void _obstack_newchunk (struct obstack *, int);
185extern int _obstack_begin (struct obstack *, int, int,
186 void *(*)(long), void (*)(void *));
187extern int _obstack_begin_1 (struct obstack *, int, int,
188 void *(*)(void *, long),
189 void (*)(void *, void *), void *);
190extern int _obstack_memory_used (struct obstack *) __attribute_pure__;
191
192/* The default name of the function for freeing a chunk is 'obstack_free',
193 but gnulib users can override this by defining '__obstack_free'. */
194#ifndef __obstack_free
195# define __obstack_free obstack_free
196#endif
197extern void __obstack_free (struct obstack *, void *);
198
199
200/* Error handler called when 'obstack_chunk_alloc' failed to allocate
201 more memory. This can be set to a user defined function which
202 should either abort gracefully or use longjump - but shouldn't
203 return. The default action is to print a message and abort. */
204extern void (*obstack_alloc_failed_handler) (void);
205
206/* Exit value used when 'print_and_abort' is used. */
207extern int obstack_exit_failure;
208
209/* Pointer to beginning of object being allocated or to be allocated next.
210 Note that this might not be the final address of the object
211 because a new chunk might be needed to hold the final size. */
212
213#define obstack_base(h) ((void *) (h)->object_base)
214
215/* Size for allocating ordinary chunks. */
216
217#define obstack_chunk_size(h) ((h)->chunk_size)
218
219/* Pointer to next byte not yet allocated in current chunk. */
220
221#define obstack_next_free(h) ((h)->next_free)
222
223/* Mask specifying low bits that should be clear in address of an object. */
224
225#define obstack_alignment_mask(h) ((h)->alignment_mask)
226
227/* To prevent prototype warnings provide complete argument list. */
228#define obstack_init(h) \
229 _obstack_begin ((h), 0, 0, \
230 (void *(*)(long))obstack_chunk_alloc, \
231 (void (*)(void *))obstack_chunk_free)
232
233#define obstack_begin(h, size) \
234 _obstack_begin ((h), (size), 0, \
235 (void *(*)(long))obstack_chunk_alloc, \
236 (void (*)(void *))obstack_chunk_free)
237
238#define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
239 _obstack_begin ((h), (size), (alignment), \
240 (void *(*)(long))(chunkfun), \
241 (void (*)(void *))(freefun))
242
243#define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
244 _obstack_begin_1 ((h), (size), (alignment), \
245 (void *(*)(void *, long))(chunkfun), \
246 (void (*)(void *, void *))(freefun), (arg))
247
248#define obstack_chunkfun(h, newchunkfun) \
249 ((h)->chunkfun = (struct _obstack_chunk *(*)(void *, long))(newchunkfun))
250
251#define obstack_freefun(h, newfreefun) \
252 ((h)->freefun = (void (*)(void *, struct _obstack_chunk *))(newfreefun))
253
254#define obstack_1grow_fast(h, achar) (*((h)->next_free)++ = (achar))
255
256#define obstack_blank_fast(h, n) ((h)->next_free += (n))
257
258#define obstack_memory_used(h) _obstack_memory_used (h)
259
260#if defined __GNUC__
261# if ! (2 < __GNUC__ + (8 <= __GNUC_MINOR__))
262# define __extension__
263# endif
264
265/* For GNU C, if not -traditional,
266 we can define these macros to compute all args only once
267 without using a global variable.
268 Also, we can avoid using the 'temp' slot, to make faster code. */
269
270# define obstack_object_size(OBSTACK) \
271 __extension__ \
272 ({ struct obstack const *__o = (OBSTACK); \
273 (unsigned) (__o->next_free - __o->object_base); })
274
275# define obstack_room(OBSTACK) \
276 __extension__ \
277 ({ struct obstack const *__o = (OBSTACK); \
278 (unsigned) (__o->chunk_limit - __o->next_free); })
279
280# define obstack_make_room(OBSTACK, length) \
281 __extension__ \
282 ({ struct obstack *__o = (OBSTACK); \
283 int __len = (length); \
284 if (__o->chunk_limit - __o->next_free < __len) \
285 _obstack_newchunk (__o, __len); \
286 (void) 0; })
287
288# define obstack_empty_p(OBSTACK) \
289 __extension__ \
290 ({ struct obstack const *__o = (OBSTACK); \
291 (__o->chunk->prev == 0 \
292 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
293 __o->chunk->contents, \
294 __o->alignment_mask)); })
295
296# define obstack_grow(OBSTACK, where, length) \
297 __extension__ \
298 ({ struct obstack *__o = (OBSTACK); \
299 int __len = (length); \
300 if (__o->next_free + __len > __o->chunk_limit) \
301 _obstack_newchunk (__o, __len); \
302 memcpy (__o->next_free, where, __len); \
303 __o->next_free += __len; \
304 (void) 0; })
305
306# define obstack_grow0(OBSTACK, where, length) \
307 __extension__ \
308 ({ struct obstack *__o = (OBSTACK); \
309 int __len = (length); \
310 if (__o->next_free + __len + 1 > __o->chunk_limit) \
311 _obstack_newchunk (__o, __len + 1); \
312 memcpy (__o->next_free, where, __len); \
313 __o->next_free += __len; \
314 *(__o->next_free)++ = 0; \
315 (void) 0; })
316
317# define obstack_1grow(OBSTACK, datum) \
318 __extension__ \
319 ({ struct obstack *__o = (OBSTACK); \
320 if (__o->next_free + 1 > __o->chunk_limit) \
321 _obstack_newchunk (__o, 1); \
322 obstack_1grow_fast (__o, datum); \
323 (void) 0; })
324
325/* These assume that the obstack alignment is good enough for pointers
326 or ints, and that the data added so far to the current object
327 shares that much alignment. */
328
329# define obstack_ptr_grow(OBSTACK, datum) \
330 __extension__ \
331 ({ struct obstack *__o = (OBSTACK); \
332 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \
333 _obstack_newchunk (__o, sizeof (void *)); \
334 obstack_ptr_grow_fast (__o, datum); }) \
335
336# define obstack_int_grow(OBSTACK, datum) \
337 __extension__ \
338 ({ struct obstack *__o = (OBSTACK); \
339 if (__o->next_free + sizeof (int) > __o->chunk_limit) \
340 _obstack_newchunk (__o, sizeof (int)); \
341 obstack_int_grow_fast (__o, datum); })
342
343# define obstack_ptr_grow_fast(OBSTACK, aptr) \
344 __extension__ \
345 ({ struct obstack *__o1 = (OBSTACK); \
346 void *__p1 = __o1->next_free; \
347 *(const void **) __p1 = (aptr); \
348 __o1->next_free += sizeof (const void *); \
349 (void) 0; })
350
351# define obstack_int_grow_fast(OBSTACK, aint) \
352 __extension__ \
353 ({ struct obstack *__o1 = (OBSTACK); \
354 void *__p1 = __o1->next_free; \
355 *(int *) __p1 = (aint); \
356 __o1->next_free += sizeof (int); \
357 (void) 0; })
358
359# define obstack_blank(OBSTACK, length) \
360 __extension__ \
361 ({ struct obstack *__o = (OBSTACK); \
362 int __len = (length); \
363 if (__o->chunk_limit - __o->next_free < __len) \
364 _obstack_newchunk (__o, __len); \
365 obstack_blank_fast (__o, __len); \
366 (void) 0; })
367
368# define obstack_alloc(OBSTACK, length) \
369 __extension__ \
370 ({ struct obstack *__h = (OBSTACK); \
371 obstack_blank (__h, (length)); \
372 obstack_finish (__h); })
373
374# define obstack_copy(OBSTACK, where, length) \
375 __extension__ \
376 ({ struct obstack *__h = (OBSTACK); \
377 obstack_grow (__h, (where), (length)); \
378 obstack_finish (__h); })
379
380# define obstack_copy0(OBSTACK, where, length) \
381 __extension__ \
382 ({ struct obstack *__h = (OBSTACK); \
383 obstack_grow0 (__h, (where), (length)); \
384 obstack_finish (__h); })
385
386/* The local variable is named __o1 to avoid a name conflict
387 when obstack_blank is called. */
388# define obstack_finish(OBSTACK) \
389 __extension__ \
390 ({ struct obstack *__o1 = (OBSTACK); \
391 void *__value = (void *) __o1->object_base; \
392 if (__o1->next_free == __value) \
393 __o1->maybe_empty_object = 1; \
394 __o1->next_free \
395 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
396 __o1->alignment_mask); \
397 if (__o1->next_free - (char *) __o1->chunk \
398 > __o1->chunk_limit - (char *) __o1->chunk) \
399 __o1->next_free = __o1->chunk_limit; \
400 __o1->object_base = __o1->next_free; \
401 __value; })
402
403# define obstack_free(OBSTACK, OBJ) \
404 __extension__ \
405 ({ struct obstack *__o = (OBSTACK); \
406 void *__obj = (OBJ); \
407 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \
408 __o->next_free = __o->object_base = (char *) __obj; \
409 else (__obstack_free) (__o, __obj); })
410
411#else /* not __GNUC__ */
412
413# define obstack_object_size(h) \
414 (unsigned) ((h)->next_free - (h)->object_base)
415
416# define obstack_room(h) \
417 (unsigned) ((h)->chunk_limit - (h)->next_free)
418
419# define obstack_empty_p(h) \
420 ((h)->chunk->prev == 0 \
421 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
422 (h)->chunk->contents, \
423 (h)->alignment_mask))
424
425/* Note that the call to _obstack_newchunk is enclosed in (..., 0)
426 so that we can avoid having void expressions
427 in the arms of the conditional expression.
428 Casting the third operand to void was tried before,
429 but some compilers won't accept it. */
430
431# define obstack_make_room(h, length) \
432 ((h)->temp.tempint = (length), \
433 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
434 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
435
436# define obstack_grow(h, where, length) \
437 ((h)->temp.tempint = (length), \
438 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
439 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
440 memcpy ((h)->next_free, where, (h)->temp.tempint), \
441 (h)->next_free += (h)->temp.tempint)
442
443# define obstack_grow0(h, where, length) \
444 ((h)->temp.tempint = (length), \
445 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \
446 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \
447 memcpy ((h)->next_free, where, (h)->temp.tempint), \
448 (h)->next_free += (h)->temp.tempint, \
449 *((h)->next_free)++ = 0)
450
451# define obstack_1grow(h, datum) \
452 ((((h)->next_free + 1 > (h)->chunk_limit) \
453 ? (_obstack_newchunk ((h), 1), 0) : 0), \
454 obstack_1grow_fast (h, datum))
455
456# define obstack_ptr_grow(h, datum) \
457 ((((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
458 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
459 obstack_ptr_grow_fast (h, datum))
460
461# define obstack_int_grow(h, datum) \
462 ((((h)->next_free + sizeof (int) > (h)->chunk_limit) \
463 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
464 obstack_int_grow_fast (h, datum))
465
466# define obstack_ptr_grow_fast(h, aptr) \
467 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
468
469# define obstack_int_grow_fast(h, aint) \
470 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
471
472# define obstack_blank(h, length) \
473 ((h)->temp.tempint = (length), \
474 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \
475 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
476 obstack_blank_fast (h, (h)->temp.tempint))
477
478# define obstack_alloc(h, length) \
479 (obstack_blank ((h), (length)), obstack_finish ((h)))
480
481# define obstack_copy(h, where, length) \
482 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
483
484# define obstack_copy0(h, where, length) \
485 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
486
487# define obstack_finish(h) \
488 (((h)->next_free == (h)->object_base \
489 ? (((h)->maybe_empty_object = 1), 0) \
490 : 0), \
491 (h)->temp.tempptr = (h)->object_base, \
492 (h)->next_free \
493 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
494 (h)->alignment_mask), \
495 (((h)->next_free - (char *) (h)->chunk \
496 > (h)->chunk_limit - (char *) (h)->chunk) \
497 ? ((h)->next_free = (h)->chunk_limit) : 0), \
498 (h)->object_base = (h)->next_free, \
499 (h)->temp.tempptr)
500
501# define obstack_free(h, obj) \
502 ((h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \
503 ((((h)->temp.tempint > 0 \
504 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \
505 ? (void) ((h)->next_free = (h)->object_base \
506 = (h)->temp.tempint + (char *) (h)->chunk) \
507 : (__obstack_free) (h, (h)->temp.tempint + (char *) (h)->chunk)))
508
509#endif /* not __GNUC__ */
510
511#ifdef __cplusplus
512} /* C++ */
513#endif
514
515#endif /* obstack.h */