1 /* obstack.h - object stack macros
2 Copyright (C) 1988-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation, either version 3 of the
8 License, or (at your option) any later version.
9
10 This file 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
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 /* Summary:
19
20 All the apparent functions defined here are macros. The idea
21 is that you would use these pre-tested macros to solve a
22 very specific set of problems, and they would run fast.
23 Caution: no side-effects in arguments please!! They may be
24 evaluated MANY times!!
25
26 These macros operate a stack of objects. Each object starts life
27 small, and may grow to maturity. (Consider building a word syllable
28 by syllable.) An object can move while it is growing. Once it has
29 been "finished" it never changes address again. So the "top of the
30 stack" is typically an immature growing object, while the rest of the
31 stack is of mature, fixed size and fixed address objects.
32
33 These routines grab large chunks of memory, using a function you
34 supply, called 'obstack_chunk_alloc'. On occasion, they free chunks,
35 by calling 'obstack_chunk_free'. You must define them and declare
36 them before using any obstack macros.
37
38 Each independent stack is represented by a 'struct obstack'.
39 Each of the obstack macros expects a pointer to such a structure
40 as the first argument.
41
42 One motivation for this package is the problem of growing char strings
43 in symbol tables. Unless you are "fascist pig with a read-only mind"
44 --Gosper's immortal quote from HAKMEM item 154, out of context--you
45 would not like to put any arbitrary upper limit on the length of your
46 symbols.
47
48 In practice this often means you will build many short symbols and a
49 few long symbols. At the time you are reading a symbol you don't know
50 how long it is. One traditional method is to read a symbol into a
51 buffer, realloc()ating the buffer every time you try to read a symbol
52 that is longer than the buffer. This is beaut, but you still will
53 want to copy the symbol from the buffer to a more permanent
54 symbol-table entry say about half the time.
55
56 With obstacks, you can work differently. Use one obstack for all symbol
57 names. As you read a symbol, grow the name in the obstack gradually.
58 When the name is complete, finalize it. Then, if the symbol exists already,
59 free the newly read name.
60
61 The way we do this is to take a large chunk, allocating memory from
62 low addresses. When you want to build a symbol in the chunk you just
63 add chars above the current "high water mark" in the chunk. When you
64 have finished adding chars, because you got to the end of the symbol,
65 you know how long the chars are, and you can create a new object.
66 Mostly the chars will not burst over the highest address of the chunk,
67 because you would typically expect a chunk to be (say) 100 times as
68 long as an average object.
69
70 In case that isn't clear, when we have enough chars to make up
71 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
72 so we just point to it where it lies. No moving of chars is
73 needed and this is the second win: potentially long strings need
74 never be explicitly shuffled. Once an object is formed, it does not
75 change its address during its lifetime.
76
77 When the chars burst over a chunk boundary, we allocate a larger
78 chunk, and then copy the partly formed object from the end of the old
79 chunk to the beginning of the new larger chunk. We then carry on
80 accreting characters to the end of the object as we normally would.
81
82 A special macro is provided to add a single char at a time to a
83 growing object. This allows the use of register variables, which
84 break the ordinary 'growth' macro.
85
86 Summary:
87 We allocate large chunks.
88 We carve out one object at a time from the current chunk.
89 Once carved, an object never moves.
90 We are free to append data of any size to the currently
91 growing object.
92 Exactly one object is growing in an obstack at any one time.
93 You can run one obstack per control block.
94 You may have as many control blocks as you dare.
95 Because of the way we do it, you can "unwind" an obstack
96 back to a previous state. (You may remove objects much
97 as you would with a stack.)
98 */
99
100
101 /* Don't do the contents of this file more than once. */
102
103 #ifndef _OBSTACK_H
104 #define _OBSTACK_H 1
105
106 /* This file uses _Noreturn, _GL_ATTRIBUTE_PURE. */
107 #if !_GL_CONFIG_H_INCLUDED
108 #error "Please include config.h first."
109 #endif
110
111 #ifndef _OBSTACK_INTERFACE_VERSION
112 # define _OBSTACK_INTERFACE_VERSION 2
113 #endif
114
115 #include <stddef.h> /* For size_t and ptrdiff_t. */
116 #include <string.h> /* For __GNU_LIBRARY__, and memcpy. */
117
118 #if __STDC_VERSION__ < 199901L || defined __HP_cc
119 # define __FLEXIBLE_ARRAY_MEMBER 1
120 #else
121 # define __FLEXIBLE_ARRAY_MEMBER
122 #endif
123
124 #if _OBSTACK_INTERFACE_VERSION == 1
125 /* For binary compatibility with obstack version 1, which used "int"
126 and "long" for these two types. */
127 # define _OBSTACK_SIZE_T unsigned int
128 # define _CHUNK_SIZE_T unsigned long
129 # define _OBSTACK_CAST(type, expr) ((type) (expr))
130 #else
131 /* Version 2 with sane types, especially for 64-bit hosts. */
132 # define _OBSTACK_SIZE_T size_t
133 # define _CHUNK_SIZE_T size_t
134 # define _OBSTACK_CAST(type, expr) (expr)
135 #endif
136
137 /* If B is the base of an object addressed by P, return the result of
138 aligning P to the next multiple of A + 1. B and P must be of type
139 char *. A + 1 must be a power of 2. */
140
141 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
142
143 /* Similar to __BPTR_ALIGN (B, P, A), except optimize the common case
144 where pointers can be converted to integers, aligned as integers,
145 and converted back again. If ptrdiff_t is narrower than a
146 pointer (e.g., the AS/400), play it safe and compute the alignment
147 relative to B. Otherwise, use the faster strategy of computing the
148 alignment relative to 0. */
149
150 #define __PTR_ALIGN(B, P, A) \
151 __BPTR_ALIGN (sizeof (ptrdiff_t) < sizeof (void *) ? (B) : (char *) 0, \
152 P, A)
153
154 #ifndef __attribute_pure__
155 # define __attribute_pure__ _GL_ATTRIBUTE_PURE
156 #endif
157
158 /* Not the same as _Noreturn, since it also works with function pointers. */
159 #ifndef __attribute_noreturn__
160 # if 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || defined __clang__ || 0x5110 <= __SUNPRO_C
161 # define __attribute_noreturn__ __attribute__ ((__noreturn__))
162 # else
163 # define __attribute_noreturn__
164 # endif
165 #endif
166
167 #ifdef __cplusplus
168 extern "C" {
169 #endif
170
171 struct _obstack_chunk /* Lives at front of each chunk. */
172 {
173 char *limit; /* 1 past end of this chunk */
174 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
175 char contents[__FLEXIBLE_ARRAY_MEMBER]; /* objects begin here */
176 };
177
178 struct obstack /* control current object in current chunk */
179 {
180 _CHUNK_SIZE_T chunk_size; /* preferred size to allocate chunks in */
181 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
182 char *object_base; /* address of object we are building */
183 char *next_free; /* where to add next char to current object */
184 char *chunk_limit; /* address of char after current chunk */
185 union
186 {
187 _OBSTACK_SIZE_T i;
188 void *p;
189 } temp; /* Temporary for some macros. */
190 _OBSTACK_SIZE_T alignment_mask; /* Mask of alignment for each object. */
191
192 /* These prototypes vary based on 'use_extra_arg'. */
193 union
194 {
195 void *(*plain) (size_t);
196 void *(*extra) (void *, size_t);
197 } chunkfun;
198 union
199 {
200 void (*plain) (void *);
201 void (*extra) (void *, void *);
202 } freefun;
203
204 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
205 unsigned use_extra_arg : 1; /* chunk alloc/dealloc funcs take extra arg */
206 unsigned maybe_empty_object : 1; /* There is a possibility that the current
207 chunk contains a zero-length object. This
208 prevents freeing the chunk if we allocate
209 a bigger chunk to replace it. */
210 unsigned alloc_failed : 1; /* No longer used, as we now call the failed
211 handler on error, but retained for binary
212 compatibility. */
213 };
214
215 /* Declare the external functions we use; they are in obstack.c. */
216
217 extern void _obstack_newchunk (struct obstack *, _OBSTACK_SIZE_T);
218 extern void _obstack_free (struct obstack *, void *);
219 extern int _obstack_begin (struct obstack *,
220 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T,
221 void *(*) (size_t), void (*) (void *));
222 extern int _obstack_begin_1 (struct obstack *,
223 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T,
224 void *(*) (void *, size_t),
225 void (*) (void *, void *), void *);
226 extern _OBSTACK_SIZE_T _obstack_memory_used (struct obstack *)
227 __attribute_pure__;
228
229
230 /* Error handler called when 'obstack_chunk_alloc' failed to allocate
231 more memory. This can be set to a user defined function which
232 should either abort gracefully or use longjump - but shouldn't
233 return. The default action is to print a message and abort. */
234 extern __attribute_noreturn__ void (*obstack_alloc_failed_handler) (void);
235
236 /* Exit value used when 'print_and_abort' is used. */
237 extern int obstack_exit_failure;
238
239 /* Pointer to beginning of object being allocated or to be allocated next.
240 Note that this might not be the final address of the object
241 because a new chunk might be needed to hold the final size. */
242
243 #define obstack_base(h) ((void *) (h)->object_base)
244
245 /* Size for allocating ordinary chunks. */
246
247 #define obstack_chunk_size(h) ((h)->chunk_size)
248
249 /* Pointer to next byte not yet allocated in current chunk. */
250
251 #define obstack_next_free(h) ((void *) (h)->next_free)
252
253 /* Mask specifying low bits that should be clear in address of an object. */
254
255 #define obstack_alignment_mask(h) ((h)->alignment_mask)
256
257 /* To prevent prototype warnings provide complete argument list. */
258 #define obstack_init(h) \
259 _obstack_begin ((h), 0, 0, \
260 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \
261 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free))
262
263 #define obstack_begin(h, size) \
264 _obstack_begin ((h), (size), 0, \
265 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \
266 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free))
267
268 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
269 _obstack_begin ((h), (size), (alignment), \
270 _OBSTACK_CAST (void *(*) (size_t), chunkfun), \
271 _OBSTACK_CAST (void (*) (void *), freefun))
272
273 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
274 _obstack_begin_1 ((h), (size), (alignment), \
275 _OBSTACK_CAST (void *(*) (void *, size_t), chunkfun), \
276 _OBSTACK_CAST (void (*) (void *, void *), freefun), arg)
277
278 #define obstack_chunkfun(h, newchunkfun) \
279 ((void) ((h)->chunkfun.extra = (void *(*) (void *, size_t)) (newchunkfun)))
280
281 #define obstack_freefun(h, newfreefun) \
282 ((void) ((h)->freefun.extra = (void *(*) (void *, void *)) (newfreefun)))
283
284 #define obstack_1grow_fast(h, achar) ((void) (*((h)->next_free)++ = (achar)))
285
286 #define obstack_blank_fast(h, n) ((void) ((h)->next_free += (n)))
287
288 #define obstack_memory_used(h) _obstack_memory_used (h)
289
290 #if defined __GNUC__ || defined __clang__
291 # if !(defined __GNUC_MINOR__ && __GNUC__ * 1000 + __GNUC_MINOR__ >= 2008 \
292 || defined __clang__)
293 # define __extension__
294 # endif
295
296 /* For GNU C, if not -traditional,
297 we can define these macros to compute all args only once
298 without using a global variable.
299 Also, we can avoid using the 'temp' slot, to make faster code. */
300
301 # define obstack_object_size(OBSTACK) \
302 __extension__ \
303 ({ struct obstack const *__o = (OBSTACK); \
304 (_OBSTACK_SIZE_T) (__o->next_free - __o->object_base); })
305
306 /* The local variable is named __o1 to avoid a shadowed variable
307 warning when invoked from other obstack macros. */
308 # define obstack_room(OBSTACK) \
309 __extension__ \
310 ({ struct obstack const *__o1 = (OBSTACK); \
311 (_OBSTACK_SIZE_T) (__o1->chunk_limit - __o1->next_free); })
312
313 # define obstack_make_room(OBSTACK, length) \
314 __extension__ \
315 ({ struct obstack *__o = (OBSTACK); \
316 _OBSTACK_SIZE_T __len = (length); \
317 if (obstack_room (__o) < __len) \
318 _obstack_newchunk (__o, __len); \
319 (void) 0; })
320
321 # define obstack_empty_p(OBSTACK) \
322 __extension__ \
323 ({ struct obstack const *__o = (OBSTACK); \
324 (__o->chunk->prev == 0 \
325 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
326 __o->chunk->contents, \
327 __o->alignment_mask)); })
328
329 # define obstack_grow(OBSTACK, where, length) \
330 __extension__ \
331 ({ struct obstack *__o = (OBSTACK); \
332 _OBSTACK_SIZE_T __len = (length); \
333 if (obstack_room (__o) < __len) \
334 _obstack_newchunk (__o, __len); \
335 memcpy (__o->next_free, where, __len); \
336 __o->next_free += __len; \
337 (void) 0; })
338
339 # define obstack_grow0(OBSTACK, where, length) \
340 __extension__ \
341 ({ struct obstack *__o = (OBSTACK); \
342 _OBSTACK_SIZE_T __len = (length); \
343 if (obstack_room (__o) < __len + 1) \
344 _obstack_newchunk (__o, __len + 1); \
345 memcpy (__o->next_free, where, __len); \
346 __o->next_free += __len; \
347 *(__o->next_free)++ = 0; \
348 (void) 0; })
349
350 # define obstack_1grow(OBSTACK, datum) \
351 __extension__ \
352 ({ struct obstack *__o = (OBSTACK); \
353 if (obstack_room (__o) < 1) \
354 _obstack_newchunk (__o, 1); \
355 obstack_1grow_fast (__o, datum); })
356
357 /* These assume that the obstack alignment is good enough for pointers
358 or ints, and that the data added so far to the current object
359 shares that much alignment. */
360
361 # define obstack_ptr_grow(OBSTACK, datum) \
362 __extension__ \
363 ({ struct obstack *__o = (OBSTACK); \
364 if (obstack_room (__o) < sizeof (void *)) \
365 _obstack_newchunk (__o, sizeof (void *)); \
366 obstack_ptr_grow_fast (__o, datum); })
367
368 # define obstack_int_grow(OBSTACK, datum) \
369 __extension__ \
370 ({ struct obstack *__o = (OBSTACK); \
371 if (obstack_room (__o) < sizeof (int)) \
372 _obstack_newchunk (__o, sizeof (int)); \
373 obstack_int_grow_fast (__o, datum); })
374
375 # define obstack_ptr_grow_fast(OBSTACK, aptr) \
376 __extension__ \
377 ({ struct obstack *__o1 = (OBSTACK); \
378 void *__p1 = __o1->next_free; \
379 *(const void **) __p1 = (aptr); \
380 __o1->next_free += sizeof (const void *); \
381 (void) 0; })
382
383 # define obstack_int_grow_fast(OBSTACK, aint) \
384 __extension__ \
385 ({ struct obstack *__o1 = (OBSTACK); \
386 void *__p1 = __o1->next_free; \
387 *(int *) __p1 = (aint); \
388 __o1->next_free += sizeof (int); \
389 (void) 0; })
390
391 # define obstack_blank(OBSTACK, length) \
392 __extension__ \
393 ({ struct obstack *__o = (OBSTACK); \
394 _OBSTACK_SIZE_T __len = (length); \
395 if (obstack_room (__o) < __len) \
396 _obstack_newchunk (__o, __len); \
397 obstack_blank_fast (__o, __len); })
398
399 # define obstack_alloc(OBSTACK, length) \
400 __extension__ \
401 ({ struct obstack *__h = (OBSTACK); \
402 obstack_blank (__h, (length)); \
403 obstack_finish (__h); })
404
405 # define obstack_copy(OBSTACK, where, length) \
406 __extension__ \
407 ({ struct obstack *__h = (OBSTACK); \
408 obstack_grow (__h, (where), (length)); \
409 obstack_finish (__h); })
410
411 # define obstack_copy0(OBSTACK, where, length) \
412 __extension__ \
413 ({ struct obstack *__h = (OBSTACK); \
414 obstack_grow0 (__h, (where), (length)); \
415 obstack_finish (__h); })
416
417 /* The local variable is named __o1 to avoid a shadowed variable
418 warning when invoked from other obstack macros, typically obstack_free. */
419 # define obstack_finish(OBSTACK) \
420 __extension__ \
421 ({ struct obstack *__o1 = (OBSTACK); \
422 void *__value = (void *) __o1->object_base; \
423 if (__o1->next_free == __value) \
424 __o1->maybe_empty_object = 1; \
425 __o1->next_free \
426 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
427 __o1->alignment_mask); \
428 if ((size_t) (__o1->next_free - (char *) __o1->chunk) \
429 > (size_t) (__o1->chunk_limit - (char *) __o1->chunk)) \
430 __o1->next_free = __o1->chunk_limit; \
431 __o1->object_base = __o1->next_free; \
432 __value; })
433
434 # define obstack_free(OBSTACK, OBJ) \
435 __extension__ \
436 ({ struct obstack *__o = (OBSTACK); \
437 void *__obj = (void *) (OBJ); \
438 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \
439 __o->next_free = __o->object_base = (char *) __obj; \
440 else \
441 _obstack_free (__o, __obj); })
442
443 #else /* not __GNUC__ */
444
445 # define obstack_object_size(h) \
446 ((_OBSTACK_SIZE_T) ((h)->next_free - (h)->object_base))
447
448 # define obstack_room(h) \
449 ((_OBSTACK_SIZE_T) ((h)->chunk_limit - (h)->next_free))
450
451 # define obstack_empty_p(h) \
452 ((h)->chunk->prev == 0 \
453 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
454 (h)->chunk->contents, \
455 (h)->alignment_mask))
456
457 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
458 so that we can avoid having void expressions
459 in the arms of the conditional expression.
460 Casting the third operand to void was tried before,
461 but some compilers won't accept it. */
462
463 # define obstack_make_room(h, length) \
464 ((h)->temp.i = (length), \
465 ((obstack_room (h) < (h)->temp.i) \
466 ? (_obstack_newchunk (h, (h)->temp.i), 0) : 0), \
467 (void) 0)
468
469 # define obstack_grow(h, where, length) \
470 ((h)->temp.i = (length), \
471 ((obstack_room (h) < (h)->temp.i) \
472 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \
473 memcpy ((h)->next_free, where, (h)->temp.i), \
474 (h)->next_free += (h)->temp.i, \
475 (void) 0)
476
477 # define obstack_grow0(h, where, length) \
478 ((h)->temp.i = (length), \
479 ((obstack_room (h) < (h)->temp.i + 1) \
480 ? (_obstack_newchunk ((h), (h)->temp.i + 1), 0) : 0), \
481 memcpy ((h)->next_free, where, (h)->temp.i), \
482 (h)->next_free += (h)->temp.i, \
483 *((h)->next_free)++ = 0, \
484 (void) 0)
485
486 # define obstack_1grow(h, datum) \
487 (((obstack_room (h) < 1) \
488 ? (_obstack_newchunk ((h), 1), 0) : 0), \
489 obstack_1grow_fast (h, datum))
490
491 # define obstack_ptr_grow(h, datum) \
492 (((obstack_room (h) < sizeof (char *)) \
493 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
494 obstack_ptr_grow_fast (h, datum))
495
496 # define obstack_int_grow(h, datum) \
497 (((obstack_room (h) < sizeof (int)) \
498 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
499 obstack_int_grow_fast (h, datum))
500
501 # define obstack_ptr_grow_fast(h, aptr) \
502 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr), \
503 (void) 0)
504
505 # define obstack_int_grow_fast(h, aint) \
506 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint), \
507 (void) 0)
508
509 # define obstack_blank(h, length) \
510 ((h)->temp.i = (length), \
511 ((obstack_room (h) < (h)->temp.i) \
512 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \
513 obstack_blank_fast (h, (h)->temp.i))
514
515 # define obstack_alloc(h, length) \
516 (obstack_blank ((h), (length)), obstack_finish ((h)))
517
518 # define obstack_copy(h, where, length) \
519 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
520
521 # define obstack_copy0(h, where, length) \
522 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
523
524 # define obstack_finish(h) \
525 (((h)->next_free == (h)->object_base \
526 ? (((h)->maybe_empty_object = 1), 0) \
527 : 0), \
528 (h)->temp.p = (h)->object_base, \
529 (h)->next_free \
530 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
531 (h)->alignment_mask), \
532 (((size_t) ((h)->next_free - (char *) (h)->chunk) \
533 > (size_t) ((h)->chunk_limit - (char *) (h)->chunk)) \
534 ? ((h)->next_free = (h)->chunk_limit) : 0), \
535 (h)->object_base = (h)->next_free, \
536 (h)->temp.p)
537
538 # define obstack_free(h, obj) \
539 ((h)->temp.p = (void *) (obj), \
540 (((h)->temp.p > (void *) (h)->chunk \
541 && (h)->temp.p < (void *) (h)->chunk_limit) \
542 ? (void) ((h)->next_free = (h)->object_base = (char *) (h)->temp.p) \
543 : _obstack_free ((h), (h)->temp.p)))
544
545 #endif /* not __GNUC__ */
546
547 #ifdef __cplusplus
548 } /* C++ */
549 #endif
550
551 #endif /* _OBSTACK_H */