Commit | Line | Data |
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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 | |
b1b57aa8 | 25 | # include <config.h> |
9d330ad0 JM |
26 | #endif |
27 | ||
029c99a3 | 28 | #ifdef HAVE_STRING_H |
b1b57aa8 | 29 | # include <string.h> |
029c99a3 RM |
30 | #endif |
31 | #ifdef HAVE_STDLIB_H | |
b1b57aa8 | 32 | # include <stdlib.h> |
029c99a3 RM |
33 | #endif |
34 | ||
2d1687d7 | 35 | #ifdef emacs |
b1b57aa8 RS |
36 | # include "lisp.h" |
37 | # include "blockinput.h" | |
2d1687d7 RS |
38 | #endif |
39 | ||
6c5c8bbe | 40 | /* If compiling with GCC 2, this file's not needed. */ |
0114e17e RM |
41 | #if !defined (__GNUC__) || __GNUC__ < 2 |
42 | ||
6c5c8bbe RM |
43 | /* If someone has defined alloca as a macro, |
44 | there must be some other way alloca is supposed to work. */ | |
b1b57aa8 | 45 | # ifndef alloca |
9d330ad0 | 46 | |
b1b57aa8 RS |
47 | # ifdef emacs |
48 | # ifdef static | |
9d330ad0 JM |
49 | /* actually, only want this if static is defined as "" |
50 | -- this is for usg, in which emacs must undefine static | |
51 | in order to make unexec workable | |
52 | */ | |
b1b57aa8 | 53 | # ifndef STACK_DIRECTION |
a8773ec1 RS |
54 | you |
55 | lose | |
56 | -- must know STACK_DIRECTION at compile-time | |
57 | /* Using #error here is not wise since this file is for | |
58 | old and obscure compilers. */ | |
b1b57aa8 RS |
59 | # endif /* STACK_DIRECTION undefined */ |
60 | # endif /* static */ | |
61 | # endif /* emacs */ | |
9d330ad0 | 62 | |
9d330ad0 JM |
63 | /* If your stack is a linked list of frames, you have to |
64 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
65 | ||
b1b57aa8 | 66 | # if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 | 67 | long i00afunc (); |
b1b57aa8 RS |
68 | # define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) |
69 | # else | |
70 | # define ADDRESS_FUNCTION(arg) &(arg) | |
71 | # endif | |
9d330ad0 | 72 | |
b1b57aa8 | 73 | # ifdef POINTER_TYPE |
29f4bda5 | 74 | typedef POINTER_TYPE *pointer; |
b1b57aa8 RS |
75 | # else /* not POINTER_TYPE */ |
76 | # if __STDC__ | |
9d330ad0 | 77 | typedef void *pointer; |
b1b57aa8 | 78 | # else /* not __STDC__ */ |
9d330ad0 | 79 | typedef char *pointer; |
b1b57aa8 RS |
80 | # endif /* not __STDC__ */ |
81 | # endif /* not POINTER_TYPE */ | |
29f4bda5 | 82 | |
b1b57aa8 RS |
83 | # ifndef NULL |
84 | # define NULL 0 | |
85 | # endif | |
9d330ad0 | 86 | |
6a7a4c07 JB |
87 | /* Different portions of Emacs need to call different versions of |
88 | malloc. The Emacs executable needs alloca to call xmalloc, because | |
89 | ordinary malloc isn't protected from input signals. On the other | |
90 | hand, the utilities in lib-src need alloca to call malloc; some of | |
91 | them are very simple, and don't have an xmalloc routine. | |
92 | ||
8fc9df9e | 93 | Non-Emacs programs expect this to call xmalloc. |
5b3bb7c6 RS |
94 | |
95 | Callers below should use malloc. */ | |
96 | ||
07e66c1e | 97 | # ifdef emacs |
b1b57aa8 RS |
98 | # undef malloc |
99 | # define malloc xmalloc | |
100 | # ifdef EMACS_FREE | |
101 | # define free EMACS_FREE | |
102 | # endif | |
103 | # endif | |
404e81d6 | 104 | extern pointer malloc (); |
6a7a4c07 | 105 | |
9d330ad0 JM |
106 | /* Define STACK_DIRECTION if you know the direction of stack |
107 | growth for your system; otherwise it will be automatically | |
108 | deduced at run-time. | |
109 | ||
110 | STACK_DIRECTION > 0 => grows toward higher addresses | |
111 | STACK_DIRECTION < 0 => grows toward lower addresses | |
112 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
113 | ||
b1b57aa8 RS |
114 | # ifndef STACK_DIRECTION |
115 | # define STACK_DIRECTION 0 /* Direction unknown. */ | |
116 | # endif | |
9d330ad0 | 117 | |
b1b57aa8 | 118 | # if STACK_DIRECTION != 0 |
9d330ad0 | 119 | |
b1b57aa8 | 120 | # define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ |
9d330ad0 | 121 | |
b1b57aa8 | 122 | # else /* STACK_DIRECTION == 0; need run-time code. */ |
9d330ad0 JM |
123 | |
124 | static int stack_dir; /* 1 or -1 once known. */ | |
b1b57aa8 | 125 | # define STACK_DIR stack_dir |
9d330ad0 JM |
126 | |
127 | static void | |
128 | find_stack_direction () | |
129 | { | |
130 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
131 | auto char dummy; /* To get stack address. */ | |
132 | ||
133 | if (addr == NULL) | |
134 | { /* Initial entry. */ | |
135 | addr = ADDRESS_FUNCTION (dummy); | |
136 | ||
137 | find_stack_direction (); /* Recurse once. */ | |
138 | } | |
139 | else | |
140 | { | |
141 | /* Second entry. */ | |
142 | if (ADDRESS_FUNCTION (dummy) > addr) | |
143 | stack_dir = 1; /* Stack grew upward. */ | |
144 | else | |
145 | stack_dir = -1; /* Stack grew downward. */ | |
146 | } | |
147 | } | |
148 | ||
b1b57aa8 | 149 | # endif /* STACK_DIRECTION == 0 */ |
9d330ad0 JM |
150 | |
151 | /* An "alloca header" is used to: | |
152 | (a) chain together all alloca'ed blocks; | |
153 | (b) keep track of stack depth. | |
154 | ||
155 | It is very important that sizeof(header) agree with malloc | |
156 | alignment chunk size. The following default should work okay. */ | |
157 | ||
b1b57aa8 RS |
158 | # ifndef ALIGN_SIZE |
159 | # define ALIGN_SIZE sizeof(double) | |
160 | # endif | |
9d330ad0 JM |
161 | |
162 | typedef union hdr | |
163 | { | |
164 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
165 | struct | |
166 | { | |
167 | union hdr *next; /* For chaining headers. */ | |
168 | char *deep; /* For stack depth measure. */ | |
169 | } h; | |
170 | } header; | |
171 | ||
172 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
173 | ||
174 | /* Return a pointer to at least SIZE bytes of storage, | |
175 | which will be automatically reclaimed upon exit from | |
176 | the procedure that called alloca. Originally, this space | |
177 | was supposed to be taken from the current stack frame of the | |
178 | caller, but that method cannot be made to work for some | |
179 | implementations of C, for example under Gould's UTX/32. */ | |
180 | ||
181 | pointer | |
182 | alloca (size) | |
183 | unsigned size; | |
184 | { | |
185 | auto char probe; /* Probes stack depth: */ | |
186 | register char *depth = ADDRESS_FUNCTION (probe); | |
187 | ||
b1b57aa8 | 188 | # if STACK_DIRECTION == 0 |
9d330ad0 JM |
189 | if (STACK_DIR == 0) /* Unknown growth direction. */ |
190 | find_stack_direction (); | |
b1b57aa8 | 191 | # endif |
9d330ad0 JM |
192 | |
193 | /* Reclaim garbage, defined as all alloca'd storage that | |
a9ddf1e8 | 194 | was allocated from deeper in the stack than currently. */ |
9d330ad0 JM |
195 | |
196 | { | |
197 | register header *hp; /* Traverses linked list. */ | |
198 | ||
b1b57aa8 | 199 | # ifdef emacs |
2d1687d7 | 200 | BLOCK_INPUT; |
b1b57aa8 | 201 | # endif |
2d1687d7 | 202 | |
9d330ad0 JM |
203 | for (hp = last_alloca_header; hp != NULL;) |
204 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
205 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
206 | { | |
207 | register header *np = hp->h.next; | |
208 | ||
209 | free ((pointer) hp); /* Collect garbage. */ | |
210 | ||
211 | hp = np; /* -> next header. */ | |
212 | } | |
213 | else | |
214 | break; /* Rest are not deeper. */ | |
215 | ||
216 | last_alloca_header = hp; /* -> last valid storage. */ | |
2d1687d7 | 217 | |
b1b57aa8 | 218 | # ifdef emacs |
2d1687d7 | 219 | UNBLOCK_INPUT; |
b1b57aa8 | 220 | # endif |
9d330ad0 JM |
221 | } |
222 | ||
223 | if (size == 0) | |
224 | return NULL; /* No allocation required. */ | |
225 | ||
226 | /* Allocate combined header + user data storage. */ | |
227 | ||
228 | { | |
02a76f8a | 229 | register pointer new = malloc (sizeof (header) + size); |
9d330ad0 JM |
230 | /* Address of header. */ |
231 | ||
e118218f KH |
232 | if (new == 0) |
233 | abort(); | |
234 | ||
9d330ad0 JM |
235 | ((header *) new)->h.next = last_alloca_header; |
236 | ((header *) new)->h.deep = depth; | |
237 | ||
238 | last_alloca_header = (header *) new; | |
239 | ||
240 | /* User storage begins just after header. */ | |
241 | ||
242 | return (pointer) ((char *) new + sizeof (header)); | |
243 | } | |
244 | } | |
245 | ||
b1b57aa8 | 246 | # if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 | 247 | |
b1b57aa8 RS |
248 | # ifdef DEBUG_I00AFUNC |
249 | # include <stdio.h> | |
250 | # endif | |
9d330ad0 | 251 | |
b1b57aa8 RS |
252 | # ifndef CRAY_STACK |
253 | # define CRAY_STACK | |
254 | # ifndef CRAY2 | |
9d330ad0 JM |
255 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ |
256 | struct stack_control_header | |
257 | { | |
258 | long shgrow:32; /* Number of times stack has grown. */ | |
259 | long shaseg:32; /* Size of increments to stack. */ | |
260 | long shhwm:32; /* High water mark of stack. */ | |
261 | long shsize:32; /* Current size of stack (all segments). */ | |
262 | }; | |
263 | ||
264 | /* The stack segment linkage control information occurs at | |
265 | the high-address end of a stack segment. (The stack | |
266 | grows from low addresses to high addresses.) The initial | |
267 | part of the stack segment linkage control information is | |
268 | 0200 (octal) words. This provides for register storage | |
269 | for the routine which overflows the stack. */ | |
270 | ||
271 | struct stack_segment_linkage | |
272 | { | |
273 | long ss[0200]; /* 0200 overflow words. */ | |
274 | long sssize:32; /* Number of words in this segment. */ | |
275 | long ssbase:32; /* Offset to stack base. */ | |
276 | long:32; | |
277 | long sspseg:32; /* Offset to linkage control of previous | |
278 | segment of stack. */ | |
279 | long:32; | |
280 | long sstcpt:32; /* Pointer to task common address block. */ | |
281 | long sscsnm; /* Private control structure number for | |
282 | microtasking. */ | |
283 | long ssusr1; /* Reserved for user. */ | |
284 | long ssusr2; /* Reserved for user. */ | |
285 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
286 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
287 | long sscray[7]; /* Reserved for Cray Research. */ | |
288 | long ssa0; | |
289 | long ssa1; | |
290 | long ssa2; | |
291 | long ssa3; | |
292 | long ssa4; | |
293 | long ssa5; | |
294 | long ssa6; | |
295 | long ssa7; | |
296 | long sss0; | |
297 | long sss1; | |
298 | long sss2; | |
299 | long sss3; | |
300 | long sss4; | |
301 | long sss5; | |
302 | long sss6; | |
303 | long sss7; | |
304 | }; | |
305 | ||
b1b57aa8 | 306 | # else /* CRAY2 */ |
9d330ad0 JM |
307 | /* The following structure defines the vector of words |
308 | returned by the STKSTAT library routine. */ | |
309 | struct stk_stat | |
310 | { | |
311 | long now; /* Current total stack size. */ | |
312 | long maxc; /* Amount of contiguous space which would | |
313 | be required to satisfy the maximum | |
314 | stack demand to date. */ | |
315 | long high_water; /* Stack high-water mark. */ | |
316 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
317 | long hits; /* Number of internal buffer hits. */ | |
318 | long extends; /* Number of block extensions. */ | |
319 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
320 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
321 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
322 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
323 | long segments; /* Current number of stack segments. */ | |
324 | long maxs; /* Maximum number of stack segments so far. */ | |
325 | long pad_size; /* Stack pad size. */ | |
326 | long current_address; /* Current stack segment address. */ | |
327 | long current_size; /* Current stack segment size. This | |
328 | number is actually corrupted by STKSTAT to | |
329 | include the fifteen word trailer area. */ | |
330 | long initial_address; /* Address of initial segment. */ | |
331 | long initial_size; /* Size of initial segment. */ | |
332 | }; | |
333 | ||
334 | /* The following structure describes the data structure which trails | |
335 | any stack segment. I think that the description in 'asdef' is | |
336 | out of date. I only describe the parts that I am sure about. */ | |
337 | ||
338 | struct stk_trailer | |
339 | { | |
340 | long this_address; /* Address of this block. */ | |
341 | long this_size; /* Size of this block (does not include | |
342 | this trailer). */ | |
343 | long unknown2; | |
344 | long unknown3; | |
345 | long link; /* Address of trailer block of previous | |
346 | segment. */ | |
347 | long unknown5; | |
348 | long unknown6; | |
349 | long unknown7; | |
350 | long unknown8; | |
351 | long unknown9; | |
352 | long unknown10; | |
353 | long unknown11; | |
354 | long unknown12; | |
355 | long unknown13; | |
356 | long unknown14; | |
357 | }; | |
358 | ||
b1b57aa8 RS |
359 | # endif /* CRAY2 */ |
360 | # endif /* not CRAY_STACK */ | |
9d330ad0 | 361 | |
b1b57aa8 | 362 | # ifdef CRAY2 |
9d330ad0 | 363 | /* Determine a "stack measure" for an arbitrary ADDRESS. |
a9ddf1e8 | 364 | I doubt that "lint" will like this much. */ |
9d330ad0 JM |
365 | |
366 | static long | |
367 | i00afunc (long *address) | |
368 | { | |
369 | struct stk_stat status; | |
370 | struct stk_trailer *trailer; | |
371 | long *block, size; | |
372 | long result = 0; | |
373 | ||
374 | /* We want to iterate through all of the segments. The first | |
375 | step is to get the stack status structure. We could do this | |
376 | more quickly and more directly, perhaps, by referencing the | |
377 | $LM00 common block, but I know that this works. */ | |
378 | ||
379 | STKSTAT (&status); | |
380 | ||
381 | /* Set up the iteration. */ | |
382 | ||
383 | trailer = (struct stk_trailer *) (status.current_address | |
384 | + status.current_size | |
385 | - 15); | |
386 | ||
387 | /* There must be at least one stack segment. Therefore it is | |
388 | a fatal error if "trailer" is null. */ | |
389 | ||
390 | if (trailer == 0) | |
391 | abort (); | |
392 | ||
393 | /* Discard segments that do not contain our argument address. */ | |
394 | ||
395 | while (trailer != 0) | |
396 | { | |
397 | block = (long *) trailer->this_address; | |
398 | size = trailer->this_size; | |
399 | if (block == 0 || size == 0) | |
400 | abort (); | |
401 | trailer = (struct stk_trailer *) trailer->link; | |
402 | if ((block <= address) && (address < (block + size))) | |
403 | break; | |
404 | } | |
405 | ||
406 | /* Set the result to the offset in this segment and add the sizes | |
407 | of all predecessor segments. */ | |
408 | ||
409 | result = address - block; | |
410 | ||
411 | if (trailer == 0) | |
412 | { | |
413 | return result; | |
414 | } | |
415 | ||
416 | do | |
417 | { | |
418 | if (trailer->this_size <= 0) | |
419 | abort (); | |
420 | result += trailer->this_size; | |
421 | trailer = (struct stk_trailer *) trailer->link; | |
422 | } | |
423 | while (trailer != 0); | |
424 | ||
425 | /* We are done. Note that if you present a bogus address (one | |
426 | not in any segment), you will get a different number back, formed | |
427 | from subtracting the address of the first block. This is probably | |
428 | not what you want. */ | |
429 | ||
430 | return (result); | |
431 | } | |
432 | ||
b1b57aa8 | 433 | # else /* not CRAY2 */ |
9d330ad0 JM |
434 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. |
435 | Determine the number of the cell within the stack, | |
436 | given the address of the cell. The purpose of this | |
437 | routine is to linearize, in some sense, stack addresses | |
438 | for alloca. */ | |
439 | ||
440 | static long | |
441 | i00afunc (long address) | |
442 | { | |
443 | long stkl = 0; | |
444 | ||
445 | long size, pseg, this_segment, stack; | |
446 | long result = 0; | |
447 | ||
448 | struct stack_segment_linkage *ssptr; | |
449 | ||
450 | /* Register B67 contains the address of the end of the | |
451 | current stack segment. If you (as a subprogram) store | |
452 | your registers on the stack and find that you are past | |
453 | the contents of B67, you have overflowed the segment. | |
454 | ||
455 | B67 also points to the stack segment linkage control | |
456 | area, which is what we are really interested in. */ | |
457 | ||
458 | stkl = CRAY_STACKSEG_END (); | |
459 | ssptr = (struct stack_segment_linkage *) stkl; | |
460 | ||
461 | /* If one subtracts 'size' from the end of the segment, | |
462 | one has the address of the first word of the segment. | |
463 | ||
464 | If this is not the first segment, 'pseg' will be | |
465 | nonzero. */ | |
466 | ||
467 | pseg = ssptr->sspseg; | |
468 | size = ssptr->sssize; | |
469 | ||
470 | this_segment = stkl - size; | |
471 | ||
472 | /* It is possible that calling this routine itself caused | |
473 | a stack overflow. Discard stack segments which do not | |
474 | contain the target address. */ | |
475 | ||
476 | while (!(this_segment <= address && address <= stkl)) | |
477 | { | |
b1b57aa8 | 478 | # ifdef DEBUG_I00AFUNC |
9d330ad0 | 479 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); |
b1b57aa8 | 480 | # endif |
9d330ad0 JM |
481 | if (pseg == 0) |
482 | break; | |
483 | stkl = stkl - pseg; | |
484 | ssptr = (struct stack_segment_linkage *) stkl; | |
485 | size = ssptr->sssize; | |
486 | pseg = ssptr->sspseg; | |
487 | this_segment = stkl - size; | |
488 | } | |
489 | ||
490 | result = address - this_segment; | |
491 | ||
492 | /* If you subtract pseg from the current end of the stack, | |
493 | you get the address of the previous stack segment's end. | |
494 | This seems a little convoluted to me, but I'll bet you save | |
495 | a cycle somewhere. */ | |
496 | ||
497 | while (pseg != 0) | |
498 | { | |
b1b57aa8 | 499 | # ifdef DEBUG_I00AFUNC |
9d330ad0 | 500 | fprintf (stderr, "%011o %011o\n", pseg, size); |
b1b57aa8 | 501 | # endif |
9d330ad0 JM |
502 | stkl = stkl - pseg; |
503 | ssptr = (struct stack_segment_linkage *) stkl; | |
504 | size = ssptr->sssize; | |
505 | pseg = ssptr->sspseg; | |
506 | result += size; | |
507 | } | |
508 | return (result); | |
509 | } | |
510 | ||
b1b57aa8 RS |
511 | # endif /* not CRAY2 */ |
512 | # endif /* CRAY */ | |
9d330ad0 | 513 | |
b1b57aa8 | 514 | # endif /* no alloca */ |
6c5c8bbe | 515 | #endif /* not GCC version 2 */ |