Change to the linux kernel coding style
[wmaker-crm.git] / wrlib / alloca.c
1 /* alloca.c -- allocate automatically reclaimed memory
2 (Mostly) portable public-domain implementation -- D A Gwyn
3
4 This implementation of the PWB library alloca function,
5 which is used to allocate space off the run-time stack so
6 that it is automatically reclaimed upon procedure exit,
7 was inspired by discussions with J. Q. Johnson of Cornell.
8 J.Otto Tennant <jot@cray.com> contributed the Cray support.
9
10 There are some preprocessor constants that can
11 be defined when compiling for your specific system, for
12 improved efficiency; however, the defaults should be okay.
13
14 The general concept of this implementation is to keep
15 track of all alloca-allocated blocks, and reclaim any
16 that are found to be deeper in the stack than the current
17 invocation. This heuristic does not reclaim storage as
18 soon as it becomes invalid, but it will do so eventually.
19
20 As a special case, alloca(0) reclaims storage without
21 allocating any. It is a good idea to use alloca(0) in
22 your main control loop, etc. to force garbage collection. */
23
24 #ifdef HAVE_CONFIG_H
25 #include <config.h>
26 #endif
27
28 #ifdef HAVE_STRING_H
29 #include <string.h>
30 #endif
31 #ifdef HAVE_STDLIB_H
32 #include <stdlib.h>
33 #endif
34
35 #ifdef emacs
36 #include "blockinput.h"
37 #endif
38
39 /* If compiling with GCC 2, this file's not needed. */
40 #if !defined (__GNUC__) || __GNUC__ < 2
41
42 /* If someone has defined alloca as a macro,
43 there must be some other way alloca is supposed to work. */
44 #ifndef alloca
45
46 #ifdef emacs
47 #ifdef static
48 /* actually, only want this if static is defined as ""
49 -- this is for usg, in which emacs must undefine static
50 in order to make unexec workable
51 */
52 #ifndef STACK_DIRECTION
53 you lose-- must know STACK_DIRECTION at compile - time
54 #endif /* STACK_DIRECTION undefined */
55 #endif /* static */
56 #endif /* emacs */
57 /* If your stack is a linked list of frames, you have to
58 provide an "address metric" ADDRESS_FUNCTION macro. */
59 #if defined (CRAY) && defined (CRAY_STACKSEG_END)
60 long i00afunc();
61 #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg))
62 #else
63 #define ADDRESS_FUNCTION(arg) &(arg)
64 #endif
65 #if __STDC__
66 typedef void *pointer;
67 #else
68 typedef char *pointer;
69 #endif
70
71 #ifndef NULL
72 #define NULL 0
73 #endif
74
75 /* Different portions of Emacs need to call different versions of
76 malloc. The Emacs executable needs alloca to call xmalloc, because
77 ordinary malloc isn't protected from input signals. On the other
78 hand, the utilities in lib-src need alloca to call malloc; some of
79 them are very simple, and don't have an xmalloc routine.
80
81 Non-Emacs programs expect this to call use xmalloc.
82
83 Callers below should use malloc. */
84
85 #ifndef emacs
86 #define malloc xmalloc
87 #endif
88 extern pointer malloc();
89
90 /* Define STACK_DIRECTION if you know the direction of stack
91 growth for your system; otherwise it will be automatically
92 deduced at run-time.
93
94 STACK_DIRECTION > 0 => grows toward higher addresses
95 STACK_DIRECTION < 0 => grows toward lower addresses
96 STACK_DIRECTION = 0 => direction of growth unknown */
97
98 #ifndef STACK_DIRECTION
99 #define STACK_DIRECTION 0 /* Direction unknown. */
100 #endif
101
102 #if STACK_DIRECTION != 0
103
104 #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */
105
106 #else /* STACK_DIRECTION == 0; need run-time code. */
107
108 static int stack_dir; /* 1 or -1 once known. */
109 #define STACK_DIR stack_dir
110
111 static void find_stack_direction()
112 {
113 static char *addr = NULL; /* Address of first `dummy', once known. */
114 auto char dummy; /* To get stack address. */
115
116 if (addr == NULL) { /* Initial entry. */
117 addr = ADDRESS_FUNCTION(dummy);
118
119 find_stack_direction(); /* Recurse once. */
120 } else {
121 /* Second entry. */
122 if (ADDRESS_FUNCTION(dummy) > addr)
123 stack_dir = 1; /* Stack grew upward. */
124 else
125 stack_dir = -1; /* Stack grew downward. */
126 }
127 }
128
129 #endif /* STACK_DIRECTION == 0 */
130
131 /* An "alloca header" is used to:
132 (a) chain together all alloca'ed blocks;
133 (b) keep track of stack depth.
134
135 It is very important that sizeof(header) agree with malloc
136 alignment chunk size. The following default should work okay. */
137
138 #ifndef ALIGN_SIZE
139 #define ALIGN_SIZE sizeof(double)
140 #endif
141
142 typedef union hdr {
143 char align[ALIGN_SIZE]; /* To force sizeof(header). */
144 struct {
145 union hdr *next; /* For chaining headers. */
146 char *deep; /* For stack depth measure. */
147 } h;
148 } header;
149
150 static header *last_alloca_header = NULL; /* -> last alloca header. */
151
152 /* Return a pointer to at least SIZE bytes of storage,
153 which will be automatically reclaimed upon exit from
154 the procedure that called alloca. Originally, this space
155 was supposed to be taken from the current stack frame of the
156 caller, but that method cannot be made to work for some
157 implementations of C, for example under Gould's UTX/32. */
158
159 pointer alloca(size)
160 unsigned size;
161 {
162 auto char probe; /* Probes stack depth: */
163 register char *depth = ADDRESS_FUNCTION(probe);
164
165 #if STACK_DIRECTION == 0
166 if (STACK_DIR == 0) /* Unknown growth direction. */
167 find_stack_direction();
168 #endif
169
170 /* Reclaim garbage, defined as all alloca'd storage that
171 was allocated from deeper in the stack than currently. */
172
173 {
174 register header *hp; /* Traverses linked list. */
175
176 #ifdef emacs
177 BLOCK_INPUT;
178 #endif
179
180 for (hp = last_alloca_header; hp != NULL;)
181 if ((STACK_DIR > 0 && hp->h.deep > depth)
182 || (STACK_DIR < 0 && hp->h.deep < depth)) {
183 register header *np = hp->h.next;
184
185 free((pointer) hp); /* Collect garbage. */
186
187 hp = np; /* -> next header. */
188 } else
189 break; /* Rest are not deeper. */
190
191 last_alloca_header = hp; /* -> last valid storage. */
192
193 #ifdef emacs
194 UNBLOCK_INPUT;
195 #endif
196 }
197
198 if (size == 0)
199 return NULL; /* No allocation required. */
200
201 /* Allocate combined header + user data storage. */
202
203 {
204 register pointer new = malloc(sizeof(header) + size);
205 /* Address of header. */
206
207 if (new == 0)
208 abort();
209
210 ((header *) new)->h.next = last_alloca_header;
211 ((header *) new)->h.deep = depth;
212
213 last_alloca_header = (header *) new;
214
215 /* User storage begins just after header. */
216
217 return (pointer) ((char *)new + sizeof(header));
218 }
219 }
220
221 #if defined (CRAY) && defined (CRAY_STACKSEG_END)
222
223 #ifdef DEBUG_I00AFUNC
224 #include <stdio.h>
225 #endif
226
227 #ifndef CRAY_STACK
228 #define CRAY_STACK
229 #ifndef CRAY2
230 /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */
231 struct stack_control_header {
232 long shgrow:32; /* Number of times stack has grown. */
233 long shaseg:32; /* Size of increments to stack. */
234 long shhwm:32; /* High water mark of stack. */
235 long shsize:32; /* Current size of stack (all segments). */
236 };
237
238 /* The stack segment linkage control information occurs at
239 the high-address end of a stack segment. (The stack
240 grows from low addresses to high addresses.) The initial
241 part of the stack segment linkage control information is
242 0200 (octal) words. This provides for register storage
243 for the routine which overflows the stack. */
244
245 struct stack_segment_linkage {
246 long ss[0200]; /* 0200 overflow words. */
247 long sssize:32; /* Number of words in this segment. */
248 long ssbase:32; /* Offset to stack base. */
249 long:32;
250 long sspseg:32; /* Offset to linkage control of previous
251 segment of stack. */
252 long:32;
253 long sstcpt:32; /* Pointer to task common address block. */
254 long sscsnm; /* Private control structure number for
255 microtasking. */
256 long ssusr1; /* Reserved for user. */
257 long ssusr2; /* Reserved for user. */
258 long sstpid; /* Process ID for pid based multi-tasking. */
259 long ssgvup; /* Pointer to multitasking thread giveup. */
260 long sscray[7]; /* Reserved for Cray Research. */
261 long ssa0;
262 long ssa1;
263 long ssa2;
264 long ssa3;
265 long ssa4;
266 long ssa5;
267 long ssa6;
268 long ssa7;
269 long sss0;
270 long sss1;
271 long sss2;
272 long sss3;
273 long sss4;
274 long sss5;
275 long sss6;
276 long sss7;
277 };
278
279 #else /* CRAY2 */
280 /* The following structure defines the vector of words
281 returned by the STKSTAT library routine. */
282 struct stk_stat {
283 long now; /* Current total stack size. */
284 long maxc; /* Amount of contiguous space which would
285 be required to satisfy the maximum
286 stack demand to date. */
287 long high_water; /* Stack high-water mark. */
288 long overflows; /* Number of stack overflow ($STKOFEN) calls. */
289 long hits; /* Number of internal buffer hits. */
290 long extends; /* Number of block extensions. */
291 long stko_mallocs; /* Block allocations by $STKOFEN. */
292 long underflows; /* Number of stack underflow calls ($STKRETN). */
293 long stko_free; /* Number of deallocations by $STKRETN. */
294 long stkm_free; /* Number of deallocations by $STKMRET. */
295 long segments; /* Current number of stack segments. */
296 long maxs; /* Maximum number of stack segments so far. */
297 long pad_size; /* Stack pad size. */
298 long current_address; /* Current stack segment address. */
299 long current_size; /* Current stack segment size. This
300 number is actually corrupted by STKSTAT to
301 include the fifteen word trailer area. */
302 long initial_address; /* Address of initial segment. */
303 long initial_size; /* Size of initial segment. */
304 };
305
306 /* The following structure describes the data structure which trails
307 any stack segment. I think that the description in 'asdef' is
308 out of date. I only describe the parts that I am sure about. */
309
310 struct stk_trailer {
311 long this_address; /* Address of this block. */
312 long this_size; /* Size of this block (does not include
313 this trailer). */
314 long unknown2;
315 long unknown3;
316 long link; /* Address of trailer block of previous
317 segment. */
318 long unknown5;
319 long unknown6;
320 long unknown7;
321 long unknown8;
322 long unknown9;
323 long unknown10;
324 long unknown11;
325 long unknown12;
326 long unknown13;
327 long unknown14;
328 };
329
330 #endif /* CRAY2 */
331 #endif /* not CRAY_STACK */
332
333 #ifdef CRAY2
334 /* Determine a "stack measure" for an arbitrary ADDRESS.
335 I doubt that "lint" will like this much. */
336
337 static long i00afunc(long *address)
338 {
339 struct stk_stat status;
340 struct stk_trailer *trailer;
341 long *block, size;
342 long result = 0;
343
344 /* We want to iterate through all of the segments. The first
345 step is to get the stack status structure. We could do this
346 more quickly and more directly, perhaps, by referencing the
347 $LM00 common block, but I know that this works. */
348
349 STKSTAT(&status);
350
351 /* Set up the iteration. */
352
353 trailer = (struct stk_trailer *)(status.current_address + status.current_size - 15);
354
355 /* There must be at least one stack segment. Therefore it is
356 a fatal error if "trailer" is null. */
357
358 if (trailer == 0)
359 abort();
360
361 /* Discard segments that do not contain our argument address. */
362
363 while (trailer != 0) {
364 block = (long *)trailer->this_address;
365 size = trailer->this_size;
366 if (block == 0 || size == 0)
367 abort();
368 trailer = (struct stk_trailer *)trailer->link;
369 if ((block <= address) && (address < (block + size)))
370 break;
371 }
372
373 /* Set the result to the offset in this segment and add the sizes
374 of all predecessor segments. */
375
376 result = address - block;
377
378 if (trailer == 0) {
379 return result;
380 }
381
382 do {
383 if (trailer->this_size <= 0)
384 abort();
385 result += trailer->this_size;
386 trailer = (struct stk_trailer *)trailer->link;
387 }
388 while (trailer != 0);
389
390 /* We are done. Note that if you present a bogus address (one
391 not in any segment), you will get a different number back, formed
392 from subtracting the address of the first block. This is probably
393 not what you want. */
394
395 return (result);
396 }
397
398 #else /* not CRAY2 */
399 /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP.
400 Determine the number of the cell within the stack,
401 given the address of the cell. The purpose of this
402 routine is to linearize, in some sense, stack addresses
403 for alloca. */
404
405 static long i00afunc(long address)
406 {
407 long stkl = 0;
408
409 long size, pseg, this_segment, stack;
410 long result = 0;
411
412 struct stack_segment_linkage *ssptr;
413
414 /* Register B67 contains the address of the end of the
415 current stack segment. If you (as a subprogram) store
416 your registers on the stack and find that you are past
417 the contents of B67, you have overflowed the segment.
418
419 B67 also points to the stack segment linkage control
420 area, which is what we are really interested in. */
421
422 stkl = CRAY_STACKSEG_END();
423 ssptr = (struct stack_segment_linkage *)stkl;
424
425 /* If one subtracts 'size' from the end of the segment,
426 one has the address of the first word of the segment.
427
428 If this is not the first segment, 'pseg' will be
429 nonzero. */
430
431 pseg = ssptr->sspseg;
432 size = ssptr->sssize;
433
434 this_segment = stkl - size;
435
436 /* It is possible that calling this routine itself caused
437 a stack overflow. Discard stack segments which do not
438 contain the target address. */
439
440 while (!(this_segment <= address && address <= stkl)) {
441 #ifdef DEBUG_I00AFUNC
442 fprintf(stderr, "%011o %011o %011o\n", this_segment, address, stkl);
443 #endif
444 if (pseg == 0)
445 break;
446 stkl = stkl - pseg;
447 ssptr = (struct stack_segment_linkage *)stkl;
448 size = ssptr->sssize;
449 pseg = ssptr->sspseg;
450 this_segment = stkl - size;
451 }
452
453 result = address - this_segment;
454
455 /* If you subtract pseg from the current end of the stack,
456 you get the address of the previous stack segment's end.
457 This seems a little convoluted to me, but I'll bet you save
458 a cycle somewhere. */
459
460 while (pseg != 0) {
461 #ifdef DEBUG_I00AFUNC
462 fprintf(stderr, "%011o %011o\n", pseg, size);
463 #endif
464 stkl = stkl - pseg;
465 ssptr = (struct stack_segment_linkage *)stkl;
466 size = ssptr->sssize;
467 pseg = ssptr->sspseg;
468 result += size;
469 }
470 return (result);
471 }
472
473 #endif /* not CRAY2 */
474 #endif /* CRAY */
475
476 #endif /* no alloca */
477 #endif /* not GCC version 2 */