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 | |
94f6013a | 25 | #include <config.h> |
9d330ad0 JM |
26 | #endif |
27 | ||
029c99a3 RM |
28 | #ifdef HAVE_STRING_H |
29 | #include <string.h> | |
30 | #endif | |
31 | #ifdef HAVE_STDLIB_H | |
32 | #include <stdlib.h> | |
33 | #endif | |
34 | ||
2d1687d7 | 35 | #ifdef emacs |
4954f4b0 | 36 | #include "lisp.h" |
2d1687d7 RS |
37 | #include "blockinput.h" |
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. */ | |
9d330ad0 JM |
45 | #ifndef alloca |
46 | ||
47 | #ifdef emacs | |
48 | #ifdef static | |
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 | */ | |
53 | #ifndef STACK_DIRECTION | |
29f4bda5 | 54 | #error "Must know STACK_DIRECTION at compile-time" |
9d330ad0 JM |
55 | #endif /* STACK_DIRECTION undefined */ |
56 | #endif /* static */ | |
57 | #endif /* emacs */ | |
58 | ||
9d330ad0 JM |
59 | /* If your stack is a linked list of frames, you have to |
60 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
61 | ||
e1efaae9 | 62 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 JM |
63 | long i00afunc (); |
64 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | |
65 | #else | |
66 | #define ADDRESS_FUNCTION(arg) &(arg) | |
67 | #endif | |
68 | ||
29f4bda5 DL |
69 | #ifdef POINTER_TYPE |
70 | typedef POINTER_TYPE *pointer; | |
71 | #else | |
9d330ad0 JM |
72 | #if __STDC__ |
73 | typedef void *pointer; | |
74 | #else | |
75 | typedef char *pointer; | |
29f4bda5 DL |
76 | #endif /*__STDC__*/ |
77 | #endif /*POINTER_TYPE*/ | |
78 | ||
9d330ad0 | 79 | |
4fd2d8e9 | 80 | #ifndef NULL |
9d330ad0 | 81 | #define NULL 0 |
4fd2d8e9 | 82 | #endif |
9d330ad0 | 83 | |
6a7a4c07 JB |
84 | /* Different portions of Emacs need to call different versions of |
85 | malloc. The Emacs executable needs alloca to call xmalloc, because | |
86 | ordinary malloc isn't protected from input signals. On the other | |
87 | hand, the utilities in lib-src need alloca to call malloc; some of | |
88 | them are very simple, and don't have an xmalloc routine. | |
89 | ||
5b3bb7c6 RS |
90 | Non-Emacs programs expect this to call use xmalloc. |
91 | ||
92 | Callers below should use malloc. */ | |
93 | ||
c87a7e0f | 94 | #ifdef emacs |
5b3bb7c6 | 95 | #define malloc xmalloc |
99d5dc12 GM |
96 | #ifdef EMACS_FREE |
97 | #define free EMACS_FREE | |
98 | #endif | |
6a7a4c07 | 99 | #endif |
404e81d6 | 100 | extern pointer malloc (); |
6a7a4c07 | 101 | |
9d330ad0 JM |
102 | /* Define STACK_DIRECTION if you know the direction of stack |
103 | growth for your system; otherwise it will be automatically | |
104 | deduced at run-time. | |
105 | ||
106 | STACK_DIRECTION > 0 => grows toward higher addresses | |
107 | STACK_DIRECTION < 0 => grows toward lower addresses | |
108 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
109 | ||
110 | #ifndef STACK_DIRECTION | |
111 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
112 | #endif | |
113 | ||
114 | #if STACK_DIRECTION != 0 | |
115 | ||
116 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
117 | ||
118 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
119 | ||
120 | static int stack_dir; /* 1 or -1 once known. */ | |
121 | #define STACK_DIR stack_dir | |
122 | ||
123 | static void | |
124 | find_stack_direction () | |
125 | { | |
126 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
127 | auto char dummy; /* To get stack address. */ | |
128 | ||
129 | if (addr == NULL) | |
130 | { /* Initial entry. */ | |
131 | addr = ADDRESS_FUNCTION (dummy); | |
132 | ||
133 | find_stack_direction (); /* Recurse once. */ | |
134 | } | |
135 | else | |
136 | { | |
137 | /* Second entry. */ | |
138 | if (ADDRESS_FUNCTION (dummy) > addr) | |
139 | stack_dir = 1; /* Stack grew upward. */ | |
140 | else | |
141 | stack_dir = -1; /* Stack grew downward. */ | |
142 | } | |
143 | } | |
144 | ||
145 | #endif /* STACK_DIRECTION == 0 */ | |
146 | ||
147 | /* An "alloca header" is used to: | |
148 | (a) chain together all alloca'ed blocks; | |
149 | (b) keep track of stack depth. | |
150 | ||
151 | It is very important that sizeof(header) agree with malloc | |
152 | alignment chunk size. The following default should work okay. */ | |
153 | ||
154 | #ifndef ALIGN_SIZE | |
155 | #define ALIGN_SIZE sizeof(double) | |
156 | #endif | |
157 | ||
158 | typedef union hdr | |
159 | { | |
160 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
161 | struct | |
162 | { | |
163 | union hdr *next; /* For chaining headers. */ | |
164 | char *deep; /* For stack depth measure. */ | |
165 | } h; | |
166 | } header; | |
167 | ||
168 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
169 | ||
170 | /* Return a pointer to at least SIZE bytes of storage, | |
171 | which will be automatically reclaimed upon exit from | |
172 | the procedure that called alloca. Originally, this space | |
173 | was supposed to be taken from the current stack frame of the | |
174 | caller, but that method cannot be made to work for some | |
175 | implementations of C, for example under Gould's UTX/32. */ | |
176 | ||
177 | pointer | |
178 | alloca (size) | |
179 | unsigned size; | |
180 | { | |
181 | auto char probe; /* Probes stack depth: */ | |
182 | register char *depth = ADDRESS_FUNCTION (probe); | |
183 | ||
184 | #if STACK_DIRECTION == 0 | |
185 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
186 | find_stack_direction (); | |
187 | #endif | |
188 | ||
189 | /* Reclaim garbage, defined as all alloca'd storage that | |
a9ddf1e8 | 190 | was allocated from deeper in the stack than currently. */ |
9d330ad0 JM |
191 | |
192 | { | |
193 | register header *hp; /* Traverses linked list. */ | |
194 | ||
2d1687d7 RS |
195 | #ifdef emacs |
196 | BLOCK_INPUT; | |
197 | #endif | |
198 | ||
9d330ad0 JM |
199 | for (hp = last_alloca_header; hp != NULL;) |
200 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
201 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
202 | { | |
203 | register header *np = hp->h.next; | |
204 | ||
205 | free ((pointer) hp); /* Collect garbage. */ | |
206 | ||
207 | hp = np; /* -> next header. */ | |
208 | } | |
209 | else | |
210 | break; /* Rest are not deeper. */ | |
211 | ||
212 | last_alloca_header = hp; /* -> last valid storage. */ | |
2d1687d7 RS |
213 | |
214 | #ifdef emacs | |
215 | UNBLOCK_INPUT; | |
216 | #endif | |
9d330ad0 JM |
217 | } |
218 | ||
219 | if (size == 0) | |
220 | return NULL; /* No allocation required. */ | |
221 | ||
222 | /* Allocate combined header + user data storage. */ | |
223 | ||
224 | { | |
02a76f8a | 225 | register pointer new = malloc (sizeof (header) + size); |
9d330ad0 JM |
226 | /* Address of header. */ |
227 | ||
e118218f KH |
228 | if (new == 0) |
229 | abort(); | |
230 | ||
9d330ad0 JM |
231 | ((header *) new)->h.next = last_alloca_header; |
232 | ((header *) new)->h.deep = depth; | |
233 | ||
234 | last_alloca_header = (header *) new; | |
235 | ||
236 | /* User storage begins just after header. */ | |
237 | ||
238 | return (pointer) ((char *) new + sizeof (header)); | |
239 | } | |
240 | } | |
241 | ||
e1efaae9 | 242 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) |
9d330ad0 JM |
243 | |
244 | #ifdef DEBUG_I00AFUNC | |
245 | #include <stdio.h> | |
246 | #endif | |
247 | ||
248 | #ifndef CRAY_STACK | |
249 | #define CRAY_STACK | |
250 | #ifndef CRAY2 | |
251 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
252 | struct stack_control_header | |
253 | { | |
254 | long shgrow:32; /* Number of times stack has grown. */ | |
255 | long shaseg:32; /* Size of increments to stack. */ | |
256 | long shhwm:32; /* High water mark of stack. */ | |
257 | long shsize:32; /* Current size of stack (all segments). */ | |
258 | }; | |
259 | ||
260 | /* The stack segment linkage control information occurs at | |
261 | the high-address end of a stack segment. (The stack | |
262 | grows from low addresses to high addresses.) The initial | |
263 | part of the stack segment linkage control information is | |
264 | 0200 (octal) words. This provides for register storage | |
265 | for the routine which overflows the stack. */ | |
266 | ||
267 | struct stack_segment_linkage | |
268 | { | |
269 | long ss[0200]; /* 0200 overflow words. */ | |
270 | long sssize:32; /* Number of words in this segment. */ | |
271 | long ssbase:32; /* Offset to stack base. */ | |
272 | long:32; | |
273 | long sspseg:32; /* Offset to linkage control of previous | |
274 | segment of stack. */ | |
275 | long:32; | |
276 | long sstcpt:32; /* Pointer to task common address block. */ | |
277 | long sscsnm; /* Private control structure number for | |
278 | microtasking. */ | |
279 | long ssusr1; /* Reserved for user. */ | |
280 | long ssusr2; /* Reserved for user. */ | |
281 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
282 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
283 | long sscray[7]; /* Reserved for Cray Research. */ | |
284 | long ssa0; | |
285 | long ssa1; | |
286 | long ssa2; | |
287 | long ssa3; | |
288 | long ssa4; | |
289 | long ssa5; | |
290 | long ssa6; | |
291 | long ssa7; | |
292 | long sss0; | |
293 | long sss1; | |
294 | long sss2; | |
295 | long sss3; | |
296 | long sss4; | |
297 | long sss5; | |
298 | long sss6; | |
299 | long sss7; | |
300 | }; | |
301 | ||
302 | #else /* CRAY2 */ | |
303 | /* The following structure defines the vector of words | |
304 | returned by the STKSTAT library routine. */ | |
305 | struct stk_stat | |
306 | { | |
307 | long now; /* Current total stack size. */ | |
308 | long maxc; /* Amount of contiguous space which would | |
309 | be required to satisfy the maximum | |
310 | stack demand to date. */ | |
311 | long high_water; /* Stack high-water mark. */ | |
312 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
313 | long hits; /* Number of internal buffer hits. */ | |
314 | long extends; /* Number of block extensions. */ | |
315 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
316 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
317 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
318 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
319 | long segments; /* Current number of stack segments. */ | |
320 | long maxs; /* Maximum number of stack segments so far. */ | |
321 | long pad_size; /* Stack pad size. */ | |
322 | long current_address; /* Current stack segment address. */ | |
323 | long current_size; /* Current stack segment size. This | |
324 | number is actually corrupted by STKSTAT to | |
325 | include the fifteen word trailer area. */ | |
326 | long initial_address; /* Address of initial segment. */ | |
327 | long initial_size; /* Size of initial segment. */ | |
328 | }; | |
329 | ||
330 | /* The following structure describes the data structure which trails | |
331 | any stack segment. I think that the description in 'asdef' is | |
332 | out of date. I only describe the parts that I am sure about. */ | |
333 | ||
334 | struct stk_trailer | |
335 | { | |
336 | long this_address; /* Address of this block. */ | |
337 | long this_size; /* Size of this block (does not include | |
338 | this trailer). */ | |
339 | long unknown2; | |
340 | long unknown3; | |
341 | long link; /* Address of trailer block of previous | |
342 | segment. */ | |
343 | long unknown5; | |
344 | long unknown6; | |
345 | long unknown7; | |
346 | long unknown8; | |
347 | long unknown9; | |
348 | long unknown10; | |
349 | long unknown11; | |
350 | long unknown12; | |
351 | long unknown13; | |
352 | long unknown14; | |
353 | }; | |
354 | ||
355 | #endif /* CRAY2 */ | |
356 | #endif /* not CRAY_STACK */ | |
357 | ||
358 | #ifdef CRAY2 | |
359 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
a9ddf1e8 | 360 | I doubt that "lint" will like this much. */ |
9d330ad0 JM |
361 | |
362 | static long | |
363 | i00afunc (long *address) | |
364 | { | |
365 | struct stk_stat status; | |
366 | struct stk_trailer *trailer; | |
367 | long *block, size; | |
368 | long result = 0; | |
369 | ||
370 | /* We want to iterate through all of the segments. The first | |
371 | step is to get the stack status structure. We could do this | |
372 | more quickly and more directly, perhaps, by referencing the | |
373 | $LM00 common block, but I know that this works. */ | |
374 | ||
375 | STKSTAT (&status); | |
376 | ||
377 | /* Set up the iteration. */ | |
378 | ||
379 | trailer = (struct stk_trailer *) (status.current_address | |
380 | + status.current_size | |
381 | - 15); | |
382 | ||
383 | /* There must be at least one stack segment. Therefore it is | |
384 | a fatal error if "trailer" is null. */ | |
385 | ||
386 | if (trailer == 0) | |
387 | abort (); | |
388 | ||
389 | /* Discard segments that do not contain our argument address. */ | |
390 | ||
391 | while (trailer != 0) | |
392 | { | |
393 | block = (long *) trailer->this_address; | |
394 | size = trailer->this_size; | |
395 | if (block == 0 || size == 0) | |
396 | abort (); | |
397 | trailer = (struct stk_trailer *) trailer->link; | |
398 | if ((block <= address) && (address < (block + size))) | |
399 | break; | |
400 | } | |
401 | ||
402 | /* Set the result to the offset in this segment and add the sizes | |
403 | of all predecessor segments. */ | |
404 | ||
405 | result = address - block; | |
406 | ||
407 | if (trailer == 0) | |
408 | { | |
409 | return result; | |
410 | } | |
411 | ||
412 | do | |
413 | { | |
414 | if (trailer->this_size <= 0) | |
415 | abort (); | |
416 | result += trailer->this_size; | |
417 | trailer = (struct stk_trailer *) trailer->link; | |
418 | } | |
419 | while (trailer != 0); | |
420 | ||
421 | /* We are done. Note that if you present a bogus address (one | |
422 | not in any segment), you will get a different number back, formed | |
423 | from subtracting the address of the first block. This is probably | |
424 | not what you want. */ | |
425 | ||
426 | return (result); | |
427 | } | |
428 | ||
429 | #else /* not CRAY2 */ | |
430 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
431 | Determine the number of the cell within the stack, | |
432 | given the address of the cell. The purpose of this | |
433 | routine is to linearize, in some sense, stack addresses | |
434 | for alloca. */ | |
435 | ||
436 | static long | |
437 | i00afunc (long address) | |
438 | { | |
439 | long stkl = 0; | |
440 | ||
441 | long size, pseg, this_segment, stack; | |
442 | long result = 0; | |
443 | ||
444 | struct stack_segment_linkage *ssptr; | |
445 | ||
446 | /* Register B67 contains the address of the end of the | |
447 | current stack segment. If you (as a subprogram) store | |
448 | your registers on the stack and find that you are past | |
449 | the contents of B67, you have overflowed the segment. | |
450 | ||
451 | B67 also points to the stack segment linkage control | |
452 | area, which is what we are really interested in. */ | |
453 | ||
454 | stkl = CRAY_STACKSEG_END (); | |
455 | ssptr = (struct stack_segment_linkage *) stkl; | |
456 | ||
457 | /* If one subtracts 'size' from the end of the segment, | |
458 | one has the address of the first word of the segment. | |
459 | ||
460 | If this is not the first segment, 'pseg' will be | |
461 | nonzero. */ | |
462 | ||
463 | pseg = ssptr->sspseg; | |
464 | size = ssptr->sssize; | |
465 | ||
466 | this_segment = stkl - size; | |
467 | ||
468 | /* It is possible that calling this routine itself caused | |
469 | a stack overflow. Discard stack segments which do not | |
470 | contain the target address. */ | |
471 | ||
472 | while (!(this_segment <= address && address <= stkl)) | |
473 | { | |
474 | #ifdef DEBUG_I00AFUNC | |
475 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
476 | #endif | |
477 | if (pseg == 0) | |
478 | break; | |
479 | stkl = stkl - pseg; | |
480 | ssptr = (struct stack_segment_linkage *) stkl; | |
481 | size = ssptr->sssize; | |
482 | pseg = ssptr->sspseg; | |
483 | this_segment = stkl - size; | |
484 | } | |
485 | ||
486 | result = address - this_segment; | |
487 | ||
488 | /* If you subtract pseg from the current end of the stack, | |
489 | you get the address of the previous stack segment's end. | |
490 | This seems a little convoluted to me, but I'll bet you save | |
491 | a cycle somewhere. */ | |
492 | ||
493 | while (pseg != 0) | |
494 | { | |
495 | #ifdef DEBUG_I00AFUNC | |
496 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
497 | #endif | |
498 | stkl = stkl - pseg; | |
499 | ssptr = (struct stack_segment_linkage *) stkl; | |
500 | size = ssptr->sssize; | |
501 | pseg = ssptr->sspseg; | |
502 | result += size; | |
503 | } | |
504 | return (result); | |
505 | } | |
506 | ||
507 | #endif /* not CRAY2 */ | |
508 | #endif /* CRAY */ | |
509 | ||
510 | #endif /* no alloca */ | |
6c5c8bbe | 511 | #endif /* not GCC version 2 */ |