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9d330ad0 JM |
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 | |
6366e5df | 25 | #if defined (emacs) || defined (CONFIG_BROKETS) |
94f6013a | 26 | #include <config.h> |
6366e5df RS |
27 | #else |
28 | #include "config.h" | |
29 | #endif | |
9d330ad0 JM |
30 | #endif |
31 | ||
6c5c8bbe | 32 | /* If compiling with GCC 2, this file's not needed. */ |
0114e17e RM |
33 | #if !defined (__GNUC__) || __GNUC__ < 2 |
34 | ||
6c5c8bbe RM |
35 | /* If someone has defined alloca as a macro, |
36 | there must be some other way alloca is supposed to work. */ | |
9d330ad0 JM |
37 | #ifndef alloca |
38 | ||
39 | #ifdef emacs | |
40 | #ifdef static | |
41 | /* actually, only want this if static is defined as "" | |
42 | -- this is for usg, in which emacs must undefine static | |
43 | in order to make unexec workable | |
44 | */ | |
45 | #ifndef STACK_DIRECTION | |
46 | you | |
47 | lose | |
48 | -- must know STACK_DIRECTION at compile-time | |
49 | #endif /* STACK_DIRECTION undefined */ | |
50 | #endif /* static */ | |
51 | #endif /* emacs */ | |
52 | ||
9d330ad0 JM |
53 | /* If your stack is a linked list of frames, you have to |
54 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
55 | ||
e1efaae9 | 56 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 JM |
57 | long i00afunc (); |
58 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | |
59 | #else | |
60 | #define ADDRESS_FUNCTION(arg) &(arg) | |
61 | #endif | |
62 | ||
63 | #if __STDC__ | |
64 | typedef void *pointer; | |
65 | #else | |
66 | typedef char *pointer; | |
67 | #endif | |
68 | ||
69 | #define NULL 0 | |
70 | ||
6a7a4c07 JB |
71 | /* Different portions of Emacs need to call different versions of |
72 | malloc. The Emacs executable needs alloca to call xmalloc, because | |
73 | ordinary malloc isn't protected from input signals. On the other | |
74 | hand, the utilities in lib-src need alloca to call malloc; some of | |
75 | them are very simple, and don't have an xmalloc routine. | |
76 | ||
5b3bb7c6 RS |
77 | Non-Emacs programs expect this to call use xmalloc. |
78 | ||
79 | Callers below should use malloc. */ | |
80 | ||
6a7a4c07 | 81 | #ifndef emacs |
5b3bb7c6 | 82 | #define malloc xmalloc |
6a7a4c07 | 83 | #endif |
404e81d6 | 84 | extern pointer malloc (); |
6a7a4c07 | 85 | |
9d330ad0 JM |
86 | /* Define STACK_DIRECTION if you know the direction of stack |
87 | growth for your system; otherwise it will be automatically | |
88 | deduced at run-time. | |
89 | ||
90 | STACK_DIRECTION > 0 => grows toward higher addresses | |
91 | STACK_DIRECTION < 0 => grows toward lower addresses | |
92 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
93 | ||
94 | #ifndef STACK_DIRECTION | |
95 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
96 | #endif | |
97 | ||
98 | #if STACK_DIRECTION != 0 | |
99 | ||
100 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
101 | ||
102 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
103 | ||
104 | static int stack_dir; /* 1 or -1 once known. */ | |
105 | #define STACK_DIR stack_dir | |
106 | ||
107 | static void | |
108 | find_stack_direction () | |
109 | { | |
110 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
111 | auto char dummy; /* To get stack address. */ | |
112 | ||
113 | if (addr == NULL) | |
114 | { /* Initial entry. */ | |
115 | addr = ADDRESS_FUNCTION (dummy); | |
116 | ||
117 | find_stack_direction (); /* Recurse once. */ | |
118 | } | |
119 | else | |
120 | { | |
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 | { | |
144 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
145 | struct | |
146 | { | |
147 | union hdr *next; /* For chaining headers. */ | |
148 | char *deep; /* For stack depth measure. */ | |
149 | } h; | |
150 | } header; | |
151 | ||
152 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
153 | ||
154 | /* Return a pointer to at least SIZE bytes of storage, | |
155 | which will be automatically reclaimed upon exit from | |
156 | the procedure that called alloca. Originally, this space | |
157 | was supposed to be taken from the current stack frame of the | |
158 | caller, but that method cannot be made to work for some | |
159 | implementations of C, for example under Gould's UTX/32. */ | |
160 | ||
161 | pointer | |
162 | alloca (size) | |
163 | unsigned size; | |
164 | { | |
165 | auto char probe; /* Probes stack depth: */ | |
166 | register char *depth = ADDRESS_FUNCTION (probe); | |
167 | ||
168 | #if STACK_DIRECTION == 0 | |
169 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
170 | find_stack_direction (); | |
171 | #endif | |
172 | ||
173 | /* Reclaim garbage, defined as all alloca'd storage that | |
174 | was allocated from deeper in the stack than currently. */ | |
175 | ||
176 | { | |
177 | register header *hp; /* Traverses linked list. */ | |
178 | ||
179 | for (hp = last_alloca_header; hp != NULL;) | |
180 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
181 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
182 | { | |
183 | register header *np = hp->h.next; | |
184 | ||
185 | free ((pointer) hp); /* Collect garbage. */ | |
186 | ||
187 | hp = np; /* -> next header. */ | |
188 | } | |
189 | else | |
190 | break; /* Rest are not deeper. */ | |
191 | ||
192 | last_alloca_header = hp; /* -> last valid storage. */ | |
193 | } | |
194 | ||
195 | if (size == 0) | |
196 | return NULL; /* No allocation required. */ | |
197 | ||
198 | /* Allocate combined header + user data storage. */ | |
199 | ||
200 | { | |
02a76f8a | 201 | register pointer new = malloc (sizeof (header) + size); |
9d330ad0 JM |
202 | /* Address of header. */ |
203 | ||
204 | ((header *) new)->h.next = last_alloca_header; | |
205 | ((header *) new)->h.deep = depth; | |
206 | ||
207 | last_alloca_header = (header *) new; | |
208 | ||
209 | /* User storage begins just after header. */ | |
210 | ||
211 | return (pointer) ((char *) new + sizeof (header)); | |
212 | } | |
213 | } | |
214 | ||
e1efaae9 | 215 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 JM |
216 | |
217 | #ifdef DEBUG_I00AFUNC | |
218 | #include <stdio.h> | |
219 | #endif | |
220 | ||
221 | #ifndef CRAY_STACK | |
222 | #define CRAY_STACK | |
223 | #ifndef CRAY2 | |
224 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
225 | struct stack_control_header | |
226 | { | |
227 | long shgrow:32; /* Number of times stack has grown. */ | |
228 | long shaseg:32; /* Size of increments to stack. */ | |
229 | long shhwm:32; /* High water mark of stack. */ | |
230 | long shsize:32; /* Current size of stack (all segments). */ | |
231 | }; | |
232 | ||
233 | /* The stack segment linkage control information occurs at | |
234 | the high-address end of a stack segment. (The stack | |
235 | grows from low addresses to high addresses.) The initial | |
236 | part of the stack segment linkage control information is | |
237 | 0200 (octal) words. This provides for register storage | |
238 | for the routine which overflows the stack. */ | |
239 | ||
240 | struct stack_segment_linkage | |
241 | { | |
242 | long ss[0200]; /* 0200 overflow words. */ | |
243 | long sssize:32; /* Number of words in this segment. */ | |
244 | long ssbase:32; /* Offset to stack base. */ | |
245 | long:32; | |
246 | long sspseg:32; /* Offset to linkage control of previous | |
247 | segment of stack. */ | |
248 | long:32; | |
249 | long sstcpt:32; /* Pointer to task common address block. */ | |
250 | long sscsnm; /* Private control structure number for | |
251 | microtasking. */ | |
252 | long ssusr1; /* Reserved for user. */ | |
253 | long ssusr2; /* Reserved for user. */ | |
254 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
255 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
256 | long sscray[7]; /* Reserved for Cray Research. */ | |
257 | long ssa0; | |
258 | long ssa1; | |
259 | long ssa2; | |
260 | long ssa3; | |
261 | long ssa4; | |
262 | long ssa5; | |
263 | long ssa6; | |
264 | long ssa7; | |
265 | long sss0; | |
266 | long sss1; | |
267 | long sss2; | |
268 | long sss3; | |
269 | long sss4; | |
270 | long sss5; | |
271 | long sss6; | |
272 | long sss7; | |
273 | }; | |
274 | ||
275 | #else /* CRAY2 */ | |
276 | /* The following structure defines the vector of words | |
277 | returned by the STKSTAT library routine. */ | |
278 | struct stk_stat | |
279 | { | |
280 | long now; /* Current total stack size. */ | |
281 | long maxc; /* Amount of contiguous space which would | |
282 | be required to satisfy the maximum | |
283 | stack demand to date. */ | |
284 | long high_water; /* Stack high-water mark. */ | |
285 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
286 | long hits; /* Number of internal buffer hits. */ | |
287 | long extends; /* Number of block extensions. */ | |
288 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
289 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
290 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
291 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
292 | long segments; /* Current number of stack segments. */ | |
293 | long maxs; /* Maximum number of stack segments so far. */ | |
294 | long pad_size; /* Stack pad size. */ | |
295 | long current_address; /* Current stack segment address. */ | |
296 | long current_size; /* Current stack segment size. This | |
297 | number is actually corrupted by STKSTAT to | |
298 | include the fifteen word trailer area. */ | |
299 | long initial_address; /* Address of initial segment. */ | |
300 | long initial_size; /* Size of initial segment. */ | |
301 | }; | |
302 | ||
303 | /* The following structure describes the data structure which trails | |
304 | any stack segment. I think that the description in 'asdef' is | |
305 | out of date. I only describe the parts that I am sure about. */ | |
306 | ||
307 | struct stk_trailer | |
308 | { | |
309 | long this_address; /* Address of this block. */ | |
310 | long this_size; /* Size of this block (does not include | |
311 | this trailer). */ | |
312 | long unknown2; | |
313 | long unknown3; | |
314 | long link; /* Address of trailer block of previous | |
315 | segment. */ | |
316 | long unknown5; | |
317 | long unknown6; | |
318 | long unknown7; | |
319 | long unknown8; | |
320 | long unknown9; | |
321 | long unknown10; | |
322 | long unknown11; | |
323 | long unknown12; | |
324 | long unknown13; | |
325 | long unknown14; | |
326 | }; | |
327 | ||
328 | #endif /* CRAY2 */ | |
329 | #endif /* not CRAY_STACK */ | |
330 | ||
331 | #ifdef CRAY2 | |
332 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
333 | I doubt that "lint" will like this much. */ | |
334 | ||
335 | static long | |
336 | i00afunc (long *address) | |
337 | { | |
338 | struct stk_stat status; | |
339 | struct stk_trailer *trailer; | |
340 | long *block, size; | |
341 | long result = 0; | |
342 | ||
343 | /* We want to iterate through all of the segments. The first | |
344 | step is to get the stack status structure. We could do this | |
345 | more quickly and more directly, perhaps, by referencing the | |
346 | $LM00 common block, but I know that this works. */ | |
347 | ||
348 | STKSTAT (&status); | |
349 | ||
350 | /* Set up the iteration. */ | |
351 | ||
352 | trailer = (struct stk_trailer *) (status.current_address | |
353 | + status.current_size | |
354 | - 15); | |
355 | ||
356 | /* There must be at least one stack segment. Therefore it is | |
357 | a fatal error if "trailer" is null. */ | |
358 | ||
359 | if (trailer == 0) | |
360 | abort (); | |
361 | ||
362 | /* Discard segments that do not contain our argument address. */ | |
363 | ||
364 | while (trailer != 0) | |
365 | { | |
366 | block = (long *) trailer->this_address; | |
367 | size = trailer->this_size; | |
368 | if (block == 0 || size == 0) | |
369 | abort (); | |
370 | trailer = (struct stk_trailer *) trailer->link; | |
371 | if ((block <= address) && (address < (block + size))) | |
372 | break; | |
373 | } | |
374 | ||
375 | /* Set the result to the offset in this segment and add the sizes | |
376 | of all predecessor segments. */ | |
377 | ||
378 | result = address - block; | |
379 | ||
380 | if (trailer == 0) | |
381 | { | |
382 | return result; | |
383 | } | |
384 | ||
385 | do | |
386 | { | |
387 | if (trailer->this_size <= 0) | |
388 | abort (); | |
389 | result += trailer->this_size; | |
390 | trailer = (struct stk_trailer *) trailer->link; | |
391 | } | |
392 | while (trailer != 0); | |
393 | ||
394 | /* We are done. Note that if you present a bogus address (one | |
395 | not in any segment), you will get a different number back, formed | |
396 | from subtracting the address of the first block. This is probably | |
397 | not what you want. */ | |
398 | ||
399 | return (result); | |
400 | } | |
401 | ||
402 | #else /* not CRAY2 */ | |
403 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
404 | Determine the number of the cell within the stack, | |
405 | given the address of the cell. The purpose of this | |
406 | routine is to linearize, in some sense, stack addresses | |
407 | for alloca. */ | |
408 | ||
409 | static long | |
410 | i00afunc (long address) | |
411 | { | |
412 | long stkl = 0; | |
413 | ||
414 | long size, pseg, this_segment, stack; | |
415 | long result = 0; | |
416 | ||
417 | struct stack_segment_linkage *ssptr; | |
418 | ||
419 | /* Register B67 contains the address of the end of the | |
420 | current stack segment. If you (as a subprogram) store | |
421 | your registers on the stack and find that you are past | |
422 | the contents of B67, you have overflowed the segment. | |
423 | ||
424 | B67 also points to the stack segment linkage control | |
425 | area, which is what we are really interested in. */ | |
426 | ||
427 | stkl = CRAY_STACKSEG_END (); | |
428 | ssptr = (struct stack_segment_linkage *) stkl; | |
429 | ||
430 | /* If one subtracts 'size' from the end of the segment, | |
431 | one has the address of the first word of the segment. | |
432 | ||
433 | If this is not the first segment, 'pseg' will be | |
434 | nonzero. */ | |
435 | ||
436 | pseg = ssptr->sspseg; | |
437 | size = ssptr->sssize; | |
438 | ||
439 | this_segment = stkl - size; | |
440 | ||
441 | /* It is possible that calling this routine itself caused | |
442 | a stack overflow. Discard stack segments which do not | |
443 | contain the target address. */ | |
444 | ||
445 | while (!(this_segment <= address && address <= stkl)) | |
446 | { | |
447 | #ifdef DEBUG_I00AFUNC | |
448 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
449 | #endif | |
450 | if (pseg == 0) | |
451 | break; | |
452 | stkl = stkl - pseg; | |
453 | ssptr = (struct stack_segment_linkage *) stkl; | |
454 | size = ssptr->sssize; | |
455 | pseg = ssptr->sspseg; | |
456 | this_segment = stkl - size; | |
457 | } | |
458 | ||
459 | result = address - this_segment; | |
460 | ||
461 | /* If you subtract pseg from the current end of the stack, | |
462 | you get the address of the previous stack segment's end. | |
463 | This seems a little convoluted to me, but I'll bet you save | |
464 | a cycle somewhere. */ | |
465 | ||
466 | while (pseg != 0) | |
467 | { | |
468 | #ifdef DEBUG_I00AFUNC | |
469 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
470 | #endif | |
471 | stkl = stkl - pseg; | |
472 | ssptr = (struct stack_segment_linkage *) stkl; | |
473 | size = ssptr->sssize; | |
474 | pseg = ssptr->sspseg; | |
475 | result += size; | |
476 | } | |
477 | return (result); | |
478 | } | |
479 | ||
480 | #endif /* not CRAY2 */ | |
481 | #endif /* CRAY */ | |
482 | ||
483 | #endif /* no alloca */ | |
6c5c8bbe | 484 | #endif /* not GCC version 2 */ |