Commit | Line | Data |
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2b6b80bc JB |
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 | ||
9b903095 RB |
24 | #if HAVE_CONFIG_H |
25 | # include <config.h> | |
26 | #endif | |
6e8d25a6 | 27 | |
a8a11001 | 28 | #include "libguile/scmconfig.h" |
2b6b80bc JB |
29 | |
30 | #ifdef HAVE_STRING_H | |
31 | #include <string.h> | |
32 | #endif | |
33 | #ifdef HAVE_STDLIB_H | |
34 | #include <stdlib.h> | |
35 | #endif | |
36 | ||
37 | #ifdef emacs | |
a0599745 | 38 | #include "libguile/blockinput.h" |
2b6b80bc JB |
39 | #endif |
40 | ||
41 | /* If compiling with GCC 2, this file's not needed. */ | |
42 | #if !defined (__GNUC__) || __GNUC__ < 2 | |
43 | ||
44 | /* If someone has defined alloca as a macro, | |
45 | there must be some other way alloca is supposed to work. */ | |
46 | #ifndef alloca | |
47 | ||
48 | #ifdef emacs | |
49 | #ifdef static | |
50 | /* actually, only want this if static is defined as "" | |
51 | -- this is for usg, in which emacs must undefine static | |
52 | in order to make unexec workable | |
53 | */ | |
54 | #ifndef STACK_DIRECTION | |
55 | you | |
56 | lose | |
57 | -- must know STACK_DIRECTION at compile-time | |
58 | #endif /* STACK_DIRECTION undefined */ | |
59 | #endif /* static */ | |
60 | #endif /* emacs */ | |
61 | ||
62 | /* If your stack is a linked list of frames, you have to | |
63 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
64 | ||
65 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
66 | long i00afunc (); | |
67 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | |
68 | #else | |
69 | #define ADDRESS_FUNCTION(arg) &(arg) | |
70 | #endif | |
71 | ||
72 | #if __STDC__ | |
73 | typedef void *pointer; | |
74 | #else | |
75 | typedef char *pointer; | |
76 | #endif | |
77 | ||
78 | #ifndef NULL | |
79 | #define NULL 0 | |
80 | #endif | |
81 | ||
2b6b80bc JB |
82 | /* Define STACK_DIRECTION if you know the direction of stack |
83 | growth for your system; otherwise it will be automatically | |
84 | deduced at run-time. | |
85 | ||
86 | STACK_DIRECTION > 0 => grows toward higher addresses | |
87 | STACK_DIRECTION < 0 => grows toward lower addresses | |
88 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
89 | ||
90 | #ifndef STACK_DIRECTION | |
91 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
92 | #endif | |
93 | ||
94 | #if STACK_DIRECTION != 0 | |
95 | ||
96 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
97 | ||
98 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
99 | ||
100 | static int stack_dir; /* 1 or -1 once known. */ | |
101 | #define STACK_DIR stack_dir | |
102 | ||
103 | static void | |
104 | find_stack_direction () | |
105 | { | |
106 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
107 | auto char dummy; /* To get stack address. */ | |
108 | ||
109 | if (addr == NULL) | |
110 | { /* Initial entry. */ | |
111 | addr = ADDRESS_FUNCTION (dummy); | |
112 | ||
113 | find_stack_direction (); /* Recurse once. */ | |
114 | } | |
115 | else | |
116 | { | |
117 | /* Second entry. */ | |
118 | if (ADDRESS_FUNCTION (dummy) > addr) | |
119 | stack_dir = 1; /* Stack grew upward. */ | |
120 | else | |
121 | stack_dir = -1; /* Stack grew downward. */ | |
122 | } | |
123 | } | |
124 | ||
125 | #endif /* STACK_DIRECTION == 0 */ | |
126 | ||
127 | /* An "alloca header" is used to: | |
128 | (a) chain together all alloca'ed blocks; | |
129 | (b) keep track of stack depth. | |
130 | ||
131 | It is very important that sizeof(header) agree with malloc | |
132 | alignment chunk size. The following default should work okay. */ | |
133 | ||
134 | #ifndef ALIGN_SIZE | |
135 | #define ALIGN_SIZE sizeof(double) | |
136 | #endif | |
137 | ||
138 | typedef union hdr | |
139 | { | |
140 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
141 | struct | |
142 | { | |
143 | union hdr *next; /* For chaining headers. */ | |
144 | char *deep; /* For stack depth measure. */ | |
145 | } h; | |
146 | } header; | |
147 | ||
148 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
149 | ||
150 | /* Return a pointer to at least SIZE bytes of storage, | |
151 | which will be automatically reclaimed upon exit from | |
152 | the procedure that called alloca. Originally, this space | |
153 | was supposed to be taken from the current stack frame of the | |
154 | caller, but that method cannot be made to work for some | |
155 | implementations of C, for example under Gould's UTX/32. */ | |
156 | ||
157 | pointer | |
6e8d25a6 | 158 | alloca (unsigned size) |
2b6b80bc JB |
159 | { |
160 | auto char probe; /* Probes stack depth: */ | |
161 | register char *depth = ADDRESS_FUNCTION (probe); | |
162 | ||
163 | #if STACK_DIRECTION == 0 | |
164 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
165 | find_stack_direction (); | |
166 | #endif | |
167 | ||
168 | /* Reclaim garbage, defined as all alloca'd storage that | |
169 | was allocated from deeper in the stack than currently. */ | |
170 | ||
171 | { | |
172 | register header *hp; /* Traverses linked list. */ | |
173 | ||
174 | #ifdef emacs | |
175 | BLOCK_INPUT; | |
176 | #endif | |
177 | ||
178 | for (hp = last_alloca_header; hp != NULL;) | |
179 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
180 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
181 | { | |
182 | register header *np = hp->h.next; | |
183 | ||
184 | free ((pointer) hp); /* Collect garbage. */ | |
185 | ||
186 | hp = np; /* -> next header. */ | |
187 | } | |
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 | { | |
67329a9e | 204 | register pointer new = (pointer) scm_malloc (sizeof (header) + size); |
2b6b80bc JB |
205 | /* Address of header. */ |
206 | ||
207 | if (new == 0) | |
f122e56e JB |
208 | { |
209 | write (2, "alloca emulation: out of memory\n", 32); | |
210 | abort(); | |
211 | } | |
2b6b80bc JB |
212 | |
213 | ((header *) new)->h.next = last_alloca_header; | |
214 | ((header *) new)->h.deep = depth; | |
215 | ||
216 | last_alloca_header = (header *) new; | |
217 | ||
218 | /* User storage begins just after header. */ | |
219 | ||
220 | return (pointer) ((char *) new + sizeof (header)); | |
221 | } | |
222 | } | |
223 | ||
224 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
225 | ||
226 | #ifdef DEBUG_I00AFUNC | |
227 | #include <stdio.h> | |
228 | #endif | |
229 | ||
230 | #ifndef CRAY_STACK | |
231 | #define CRAY_STACK | |
232 | #ifndef CRAY2 | |
233 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
234 | struct stack_control_header | |
235 | { | |
236 | long shgrow:32; /* Number of times stack has grown. */ | |
237 | long shaseg:32; /* Size of increments to stack. */ | |
238 | long shhwm:32; /* High water mark of stack. */ | |
239 | long shsize:32; /* Current size of stack (all segments). */ | |
240 | }; | |
241 | ||
242 | /* The stack segment linkage control information occurs at | |
243 | the high-address end of a stack segment. (The stack | |
244 | grows from low addresses to high addresses.) The initial | |
245 | part of the stack segment linkage control information is | |
246 | 0200 (octal) words. This provides for register storage | |
247 | for the routine which overflows the stack. */ | |
248 | ||
249 | struct stack_segment_linkage | |
250 | { | |
251 | long ss[0200]; /* 0200 overflow words. */ | |
252 | long sssize:32; /* Number of words in this segment. */ | |
253 | long ssbase:32; /* Offset to stack base. */ | |
254 | long:32; | |
255 | long sspseg:32; /* Offset to linkage control of previous | |
256 | segment of stack. */ | |
257 | long:32; | |
258 | long sstcpt:32; /* Pointer to task common address block. */ | |
259 | long sscsnm; /* Private control structure number for | |
260 | microtasking. */ | |
261 | long ssusr1; /* Reserved for user. */ | |
262 | long ssusr2; /* Reserved for user. */ | |
263 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
264 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
265 | long sscray[7]; /* Reserved for Cray Research. */ | |
266 | long ssa0; | |
267 | long ssa1; | |
268 | long ssa2; | |
269 | long ssa3; | |
270 | long ssa4; | |
271 | long ssa5; | |
272 | long ssa6; | |
273 | long ssa7; | |
274 | long sss0; | |
275 | long sss1; | |
276 | long sss2; | |
277 | long sss3; | |
278 | long sss4; | |
279 | long sss5; | |
280 | long sss6; | |
281 | long sss7; | |
282 | }; | |
283 | ||
284 | #else /* CRAY2 */ | |
285 | /* The following structure defines the vector of words | |
286 | returned by the STKSTAT library routine. */ | |
287 | struct stk_stat | |
288 | { | |
289 | long now; /* Current total stack size. */ | |
290 | long maxc; /* Amount of contiguous space which would | |
291 | be required to satisfy the maximum | |
292 | stack demand to date. */ | |
293 | long high_water; /* Stack high-water mark. */ | |
294 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
295 | long hits; /* Number of internal buffer hits. */ | |
296 | long extends; /* Number of block extensions. */ | |
297 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
298 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
299 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
300 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
301 | long segments; /* Current number of stack segments. */ | |
302 | long maxs; /* Maximum number of stack segments so far. */ | |
303 | long pad_size; /* Stack pad size. */ | |
304 | long current_address; /* Current stack segment address. */ | |
305 | long current_size; /* Current stack segment size. This | |
306 | number is actually corrupted by STKSTAT to | |
307 | include the fifteen word trailer area. */ | |
308 | long initial_address; /* Address of initial segment. */ | |
309 | long initial_size; /* Size of initial segment. */ | |
310 | }; | |
311 | ||
312 | /* The following structure describes the data structure which trails | |
313 | any stack segment. I think that the description in 'asdef' is | |
314 | out of date. I only describe the parts that I am sure about. */ | |
315 | ||
316 | struct stk_trailer | |
317 | { | |
318 | long this_address; /* Address of this block. */ | |
319 | long this_size; /* Size of this block (does not include | |
320 | this trailer). */ | |
321 | long unknown2; | |
322 | long unknown3; | |
323 | long link; /* Address of trailer block of previous | |
324 | segment. */ | |
325 | long unknown5; | |
326 | long unknown6; | |
327 | long unknown7; | |
328 | long unknown8; | |
329 | long unknown9; | |
330 | long unknown10; | |
331 | long unknown11; | |
332 | long unknown12; | |
333 | long unknown13; | |
334 | long unknown14; | |
335 | }; | |
336 | ||
337 | #endif /* CRAY2 */ | |
338 | #endif /* not CRAY_STACK */ | |
339 | ||
340 | #ifdef CRAY2 | |
341 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
342 | I doubt that "lint" will like this much. */ | |
343 | ||
344 | static long | |
345 | i00afunc (long *address) | |
346 | { | |
347 | struct stk_stat status; | |
348 | struct stk_trailer *trailer; | |
349 | long *block, size; | |
350 | long result = 0; | |
351 | ||
352 | /* We want to iterate through all of the segments. The first | |
353 | step is to get the stack status structure. We could do this | |
354 | more quickly and more directly, perhaps, by referencing the | |
355 | $LM00 common block, but I know that this works. */ | |
356 | ||
357 | STKSTAT (&status); | |
358 | ||
359 | /* Set up the iteration. */ | |
360 | ||
361 | trailer = (struct stk_trailer *) (status.current_address | |
362 | + status.current_size | |
363 | - 15); | |
364 | ||
365 | /* There must be at least one stack segment. Therefore it is | |
366 | a fatal error if "trailer" is null. */ | |
367 | ||
368 | if (trailer == 0) | |
369 | abort (); | |
370 | ||
371 | /* Discard segments that do not contain our argument address. */ | |
372 | ||
373 | while (trailer != 0) | |
374 | { | |
375 | block = (long *) trailer->this_address; | |
376 | size = trailer->this_size; | |
377 | if (block == 0 || size == 0) | |
378 | abort (); | |
379 | trailer = (struct stk_trailer *) trailer->link; | |
380 | if ((block <= address) && (address < (block + size))) | |
381 | break; | |
382 | } | |
383 | ||
384 | /* Set the result to the offset in this segment and add the sizes | |
385 | of all predecessor segments. */ | |
386 | ||
387 | result = address - block; | |
388 | ||
389 | if (trailer == 0) | |
390 | { | |
391 | return result; | |
392 | } | |
393 | ||
394 | do | |
395 | { | |
396 | if (trailer->this_size <= 0) | |
397 | abort (); | |
398 | result += trailer->this_size; | |
399 | trailer = (struct stk_trailer *) trailer->link; | |
400 | } | |
401 | while (trailer != 0); | |
402 | ||
403 | /* We are done. Note that if you present a bogus address (one | |
404 | not in any segment), you will get a different number back, formed | |
405 | from subtracting the address of the first block. This is probably | |
406 | not what you want. */ | |
407 | ||
408 | return (result); | |
409 | } | |
410 | ||
411 | #else /* not CRAY2 */ | |
412 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
413 | Determine the number of the cell within the stack, | |
414 | given the address of the cell. The purpose of this | |
415 | routine is to linearize, in some sense, stack addresses | |
416 | for alloca. */ | |
417 | ||
418 | static long | |
419 | i00afunc (long address) | |
420 | { | |
421 | long stkl = 0; | |
422 | ||
423 | long size, pseg, this_segment, stack; | |
424 | long result = 0; | |
425 | ||
426 | struct stack_segment_linkage *ssptr; | |
427 | ||
428 | /* Register B67 contains the address of the end of the | |
429 | current stack segment. If you (as a subprogram) store | |
430 | your registers on the stack and find that you are past | |
431 | the contents of B67, you have overflowed the segment. | |
432 | ||
433 | B67 also points to the stack segment linkage control | |
434 | area, which is what we are really interested in. */ | |
435 | ||
436 | stkl = CRAY_STACKSEG_END (); | |
437 | ssptr = (struct stack_segment_linkage *) stkl; | |
438 | ||
439 | /* If one subtracts 'size' from the end of the segment, | |
440 | one has the address of the first word of the segment. | |
441 | ||
442 | If this is not the first segment, 'pseg' will be | |
443 | nonzero. */ | |
444 | ||
445 | pseg = ssptr->sspseg; | |
446 | size = ssptr->sssize; | |
447 | ||
448 | this_segment = stkl - size; | |
449 | ||
450 | /* It is possible that calling this routine itself caused | |
451 | a stack overflow. Discard stack segments which do not | |
452 | contain the target address. */ | |
453 | ||
454 | while (!(this_segment <= address && address <= stkl)) | |
455 | { | |
456 | #ifdef DEBUG_I00AFUNC | |
457 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
458 | #endif | |
459 | if (pseg == 0) | |
460 | break; | |
461 | stkl = stkl - pseg; | |
462 | ssptr = (struct stack_segment_linkage *) stkl; | |
463 | size = ssptr->sssize; | |
464 | pseg = ssptr->sspseg; | |
465 | this_segment = stkl - size; | |
466 | } | |
467 | ||
468 | result = address - this_segment; | |
469 | ||
470 | /* If you subtract pseg from the current end of the stack, | |
471 | you get the address of the previous stack segment's end. | |
472 | This seems a little convoluted to me, but I'll bet you save | |
473 | a cycle somewhere. */ | |
474 | ||
475 | while (pseg != 0) | |
476 | { | |
477 | #ifdef DEBUG_I00AFUNC | |
478 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
479 | #endif | |
480 | stkl = stkl - pseg; | |
481 | ssptr = (struct stack_segment_linkage *) stkl; | |
482 | size = ssptr->sssize; | |
483 | pseg = ssptr->sspseg; | |
484 | result += size; | |
485 | } | |
486 | return (result); | |
487 | } | |
488 | ||
489 | #endif /* not CRAY2 */ | |
490 | #endif /* CRAY */ | |
491 | ||
492 | #endif /* no alloca */ | |
493 | #endif /* not GCC version 2 */ | |
89e00824 ML |
494 | |
495 | /* | |
496 | Local Variables: | |
497 | c-file-style: "gnu" | |
498 | End: | |
499 | */ |