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 | ||
6e8d25a6 | 24 | |
2b6b80bc | 25 | #ifdef HAVE_CONFIG_H |
a8a11001 | 26 | #include "libguile/scmconfig.h" |
2b6b80bc JB |
27 | #endif |
28 | ||
29 | #ifdef HAVE_STRING_H | |
30 | #include <string.h> | |
31 | #endif | |
32 | #ifdef HAVE_STDLIB_H | |
33 | #include <stdlib.h> | |
34 | #endif | |
35 | ||
36 | #ifdef emacs | |
a0599745 | 37 | #include "libguile/blockinput.h" |
2b6b80bc JB |
38 | #endif |
39 | ||
40 | /* If compiling with GCC 2, this file's not needed. */ | |
41 | #if !defined (__GNUC__) || __GNUC__ < 2 | |
42 | ||
43 | /* If someone has defined alloca as a macro, | |
44 | there must be some other way alloca is supposed to work. */ | |
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 | |
54 | you | |
55 | lose | |
56 | -- must know STACK_DIRECTION at compile-time | |
57 | #endif /* STACK_DIRECTION undefined */ | |
58 | #endif /* static */ | |
59 | #endif /* emacs */ | |
60 | ||
61 | /* If your stack is a linked list of frames, you have to | |
62 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
63 | ||
64 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
65 | long i00afunc (); | |
66 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | |
67 | #else | |
68 | #define ADDRESS_FUNCTION(arg) &(arg) | |
69 | #endif | |
70 | ||
71 | #if __STDC__ | |
72 | typedef void *pointer; | |
73 | #else | |
74 | typedef char *pointer; | |
75 | #endif | |
76 | ||
77 | #ifndef NULL | |
78 | #define NULL 0 | |
79 | #endif | |
80 | ||
2b6b80bc JB |
81 | /* Define STACK_DIRECTION if you know the direction of stack |
82 | growth for your system; otherwise it will be automatically | |
83 | deduced at run-time. | |
84 | ||
85 | STACK_DIRECTION > 0 => grows toward higher addresses | |
86 | STACK_DIRECTION < 0 => grows toward lower addresses | |
87 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
88 | ||
89 | #ifndef STACK_DIRECTION | |
90 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
91 | #endif | |
92 | ||
93 | #if STACK_DIRECTION != 0 | |
94 | ||
95 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
96 | ||
97 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
98 | ||
99 | static int stack_dir; /* 1 or -1 once known. */ | |
100 | #define STACK_DIR stack_dir | |
101 | ||
102 | static void | |
103 | find_stack_direction () | |
104 | { | |
105 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
106 | auto char dummy; /* To get stack address. */ | |
107 | ||
108 | if (addr == NULL) | |
109 | { /* Initial entry. */ | |
110 | addr = ADDRESS_FUNCTION (dummy); | |
111 | ||
112 | find_stack_direction (); /* Recurse once. */ | |
113 | } | |
114 | else | |
115 | { | |
116 | /* Second entry. */ | |
117 | if (ADDRESS_FUNCTION (dummy) > addr) | |
118 | stack_dir = 1; /* Stack grew upward. */ | |
119 | else | |
120 | stack_dir = -1; /* Stack grew downward. */ | |
121 | } | |
122 | } | |
123 | ||
124 | #endif /* STACK_DIRECTION == 0 */ | |
125 | ||
126 | /* An "alloca header" is used to: | |
127 | (a) chain together all alloca'ed blocks; | |
128 | (b) keep track of stack depth. | |
129 | ||
130 | It is very important that sizeof(header) agree with malloc | |
131 | alignment chunk size. The following default should work okay. */ | |
132 | ||
133 | #ifndef ALIGN_SIZE | |
134 | #define ALIGN_SIZE sizeof(double) | |
135 | #endif | |
136 | ||
137 | typedef union hdr | |
138 | { | |
139 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
140 | struct | |
141 | { | |
142 | union hdr *next; /* For chaining headers. */ | |
143 | char *deep; /* For stack depth measure. */ | |
144 | } h; | |
145 | } header; | |
146 | ||
147 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
148 | ||
149 | /* Return a pointer to at least SIZE bytes of storage, | |
150 | which will be automatically reclaimed upon exit from | |
151 | the procedure that called alloca. Originally, this space | |
152 | was supposed to be taken from the current stack frame of the | |
153 | caller, but that method cannot be made to work for some | |
154 | implementations of C, for example under Gould's UTX/32. */ | |
155 | ||
156 | pointer | |
6e8d25a6 | 157 | alloca (unsigned size) |
2b6b80bc JB |
158 | { |
159 | auto char probe; /* Probes stack depth: */ | |
160 | register char *depth = ADDRESS_FUNCTION (probe); | |
161 | ||
162 | #if STACK_DIRECTION == 0 | |
163 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
164 | find_stack_direction (); | |
165 | #endif | |
166 | ||
167 | /* Reclaim garbage, defined as all alloca'd storage that | |
168 | was allocated from deeper in the stack than currently. */ | |
169 | ||
170 | { | |
171 | register header *hp; /* Traverses linked list. */ | |
172 | ||
173 | #ifdef emacs | |
174 | BLOCK_INPUT; | |
175 | #endif | |
176 | ||
177 | for (hp = last_alloca_header; hp != NULL;) | |
178 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
179 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
180 | { | |
181 | register header *np = hp->h.next; | |
182 | ||
183 | free ((pointer) hp); /* Collect garbage. */ | |
184 | ||
185 | hp = np; /* -> next header. */ | |
186 | } | |
187 | else | |
188 | break; /* Rest are not deeper. */ | |
189 | ||
190 | last_alloca_header = hp; /* -> last valid storage. */ | |
191 | ||
192 | #ifdef emacs | |
193 | UNBLOCK_INPUT; | |
194 | #endif | |
195 | } | |
196 | ||
197 | if (size == 0) | |
198 | return NULL; /* No allocation required. */ | |
199 | ||
200 | /* Allocate combined header + user data storage. */ | |
201 | ||
202 | { | |
a0a06f41 | 203 | register pointer new = (pointer) malloc (sizeof (header) + size); |
2b6b80bc JB |
204 | /* Address of header. */ |
205 | ||
206 | if (new == 0) | |
f122e56e JB |
207 | { |
208 | write (2, "alloca emulation: out of memory\n", 32); | |
209 | abort(); | |
210 | } | |
2b6b80bc JB |
211 | |
212 | ((header *) new)->h.next = last_alloca_header; | |
213 | ((header *) new)->h.deep = depth; | |
214 | ||
215 | last_alloca_header = (header *) new; | |
216 | ||
217 | /* User storage begins just after header. */ | |
218 | ||
219 | return (pointer) ((char *) new + sizeof (header)); | |
220 | } | |
221 | } | |
222 | ||
223 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
224 | ||
225 | #ifdef DEBUG_I00AFUNC | |
226 | #include <stdio.h> | |
227 | #endif | |
228 | ||
229 | #ifndef CRAY_STACK | |
230 | #define CRAY_STACK | |
231 | #ifndef CRAY2 | |
232 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
233 | struct stack_control_header | |
234 | { | |
235 | long shgrow:32; /* Number of times stack has grown. */ | |
236 | long shaseg:32; /* Size of increments to stack. */ | |
237 | long shhwm:32; /* High water mark of stack. */ | |
238 | long shsize:32; /* Current size of stack (all segments). */ | |
239 | }; | |
240 | ||
241 | /* The stack segment linkage control information occurs at | |
242 | the high-address end of a stack segment. (The stack | |
243 | grows from low addresses to high addresses.) The initial | |
244 | part of the stack segment linkage control information is | |
245 | 0200 (octal) words. This provides for register storage | |
246 | for the routine which overflows the stack. */ | |
247 | ||
248 | struct stack_segment_linkage | |
249 | { | |
250 | long ss[0200]; /* 0200 overflow words. */ | |
251 | long sssize:32; /* Number of words in this segment. */ | |
252 | long ssbase:32; /* Offset to stack base. */ | |
253 | long:32; | |
254 | long sspseg:32; /* Offset to linkage control of previous | |
255 | segment of stack. */ | |
256 | long:32; | |
257 | long sstcpt:32; /* Pointer to task common address block. */ | |
258 | long sscsnm; /* Private control structure number for | |
259 | microtasking. */ | |
260 | long ssusr1; /* Reserved for user. */ | |
261 | long ssusr2; /* Reserved for user. */ | |
262 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
263 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
264 | long sscray[7]; /* Reserved for Cray Research. */ | |
265 | long ssa0; | |
266 | long ssa1; | |
267 | long ssa2; | |
268 | long ssa3; | |
269 | long ssa4; | |
270 | long ssa5; | |
271 | long ssa6; | |
272 | long ssa7; | |
273 | long sss0; | |
274 | long sss1; | |
275 | long sss2; | |
276 | long sss3; | |
277 | long sss4; | |
278 | long sss5; | |
279 | long sss6; | |
280 | long sss7; | |
281 | }; | |
282 | ||
283 | #else /* CRAY2 */ | |
284 | /* The following structure defines the vector of words | |
285 | returned by the STKSTAT library routine. */ | |
286 | struct stk_stat | |
287 | { | |
288 | long now; /* Current total stack size. */ | |
289 | long maxc; /* Amount of contiguous space which would | |
290 | be required to satisfy the maximum | |
291 | stack demand to date. */ | |
292 | long high_water; /* Stack high-water mark. */ | |
293 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
294 | long hits; /* Number of internal buffer hits. */ | |
295 | long extends; /* Number of block extensions. */ | |
296 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
297 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
298 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
299 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
300 | long segments; /* Current number of stack segments. */ | |
301 | long maxs; /* Maximum number of stack segments so far. */ | |
302 | long pad_size; /* Stack pad size. */ | |
303 | long current_address; /* Current stack segment address. */ | |
304 | long current_size; /* Current stack segment size. This | |
305 | number is actually corrupted by STKSTAT to | |
306 | include the fifteen word trailer area. */ | |
307 | long initial_address; /* Address of initial segment. */ | |
308 | long initial_size; /* Size of initial segment. */ | |
309 | }; | |
310 | ||
311 | /* The following structure describes the data structure which trails | |
312 | any stack segment. I think that the description in 'asdef' is | |
313 | out of date. I only describe the parts that I am sure about. */ | |
314 | ||
315 | struct stk_trailer | |
316 | { | |
317 | long this_address; /* Address of this block. */ | |
318 | long this_size; /* Size of this block (does not include | |
319 | this trailer). */ | |
320 | long unknown2; | |
321 | long unknown3; | |
322 | long link; /* Address of trailer block of previous | |
323 | segment. */ | |
324 | long unknown5; | |
325 | long unknown6; | |
326 | long unknown7; | |
327 | long unknown8; | |
328 | long unknown9; | |
329 | long unknown10; | |
330 | long unknown11; | |
331 | long unknown12; | |
332 | long unknown13; | |
333 | long unknown14; | |
334 | }; | |
335 | ||
336 | #endif /* CRAY2 */ | |
337 | #endif /* not CRAY_STACK */ | |
338 | ||
339 | #ifdef CRAY2 | |
340 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
341 | I doubt that "lint" will like this much. */ | |
342 | ||
343 | static long | |
344 | i00afunc (long *address) | |
345 | { | |
346 | struct stk_stat status; | |
347 | struct stk_trailer *trailer; | |
348 | long *block, size; | |
349 | long result = 0; | |
350 | ||
351 | /* We want to iterate through all of the segments. The first | |
352 | step is to get the stack status structure. We could do this | |
353 | more quickly and more directly, perhaps, by referencing the | |
354 | $LM00 common block, but I know that this works. */ | |
355 | ||
356 | STKSTAT (&status); | |
357 | ||
358 | /* Set up the iteration. */ | |
359 | ||
360 | trailer = (struct stk_trailer *) (status.current_address | |
361 | + status.current_size | |
362 | - 15); | |
363 | ||
364 | /* There must be at least one stack segment. Therefore it is | |
365 | a fatal error if "trailer" is null. */ | |
366 | ||
367 | if (trailer == 0) | |
368 | abort (); | |
369 | ||
370 | /* Discard segments that do not contain our argument address. */ | |
371 | ||
372 | while (trailer != 0) | |
373 | { | |
374 | block = (long *) trailer->this_address; | |
375 | size = trailer->this_size; | |
376 | if (block == 0 || size == 0) | |
377 | abort (); | |
378 | trailer = (struct stk_trailer *) trailer->link; | |
379 | if ((block <= address) && (address < (block + size))) | |
380 | break; | |
381 | } | |
382 | ||
383 | /* Set the result to the offset in this segment and add the sizes | |
384 | of all predecessor segments. */ | |
385 | ||
386 | result = address - block; | |
387 | ||
388 | if (trailer == 0) | |
389 | { | |
390 | return result; | |
391 | } | |
392 | ||
393 | do | |
394 | { | |
395 | if (trailer->this_size <= 0) | |
396 | abort (); | |
397 | result += trailer->this_size; | |
398 | trailer = (struct stk_trailer *) trailer->link; | |
399 | } | |
400 | while (trailer != 0); | |
401 | ||
402 | /* We are done. Note that if you present a bogus address (one | |
403 | not in any segment), you will get a different number back, formed | |
404 | from subtracting the address of the first block. This is probably | |
405 | not what you want. */ | |
406 | ||
407 | return (result); | |
408 | } | |
409 | ||
410 | #else /* not CRAY2 */ | |
411 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
412 | Determine the number of the cell within the stack, | |
413 | given the address of the cell. The purpose of this | |
414 | routine is to linearize, in some sense, stack addresses | |
415 | for alloca. */ | |
416 | ||
417 | static long | |
418 | i00afunc (long address) | |
419 | { | |
420 | long stkl = 0; | |
421 | ||
422 | long size, pseg, this_segment, stack; | |
423 | long result = 0; | |
424 | ||
425 | struct stack_segment_linkage *ssptr; | |
426 | ||
427 | /* Register B67 contains the address of the end of the | |
428 | current stack segment. If you (as a subprogram) store | |
429 | your registers on the stack and find that you are past | |
430 | the contents of B67, you have overflowed the segment. | |
431 | ||
432 | B67 also points to the stack segment linkage control | |
433 | area, which is what we are really interested in. */ | |
434 | ||
435 | stkl = CRAY_STACKSEG_END (); | |
436 | ssptr = (struct stack_segment_linkage *) stkl; | |
437 | ||
438 | /* If one subtracts 'size' from the end of the segment, | |
439 | one has the address of the first word of the segment. | |
440 | ||
441 | If this is not the first segment, 'pseg' will be | |
442 | nonzero. */ | |
443 | ||
444 | pseg = ssptr->sspseg; | |
445 | size = ssptr->sssize; | |
446 | ||
447 | this_segment = stkl - size; | |
448 | ||
449 | /* It is possible that calling this routine itself caused | |
450 | a stack overflow. Discard stack segments which do not | |
451 | contain the target address. */ | |
452 | ||
453 | while (!(this_segment <= address && address <= stkl)) | |
454 | { | |
455 | #ifdef DEBUG_I00AFUNC | |
456 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
457 | #endif | |
458 | if (pseg == 0) | |
459 | break; | |
460 | stkl = stkl - pseg; | |
461 | ssptr = (struct stack_segment_linkage *) stkl; | |
462 | size = ssptr->sssize; | |
463 | pseg = ssptr->sspseg; | |
464 | this_segment = stkl - size; | |
465 | } | |
466 | ||
467 | result = address - this_segment; | |
468 | ||
469 | /* If you subtract pseg from the current end of the stack, | |
470 | you get the address of the previous stack segment's end. | |
471 | This seems a little convoluted to me, but I'll bet you save | |
472 | a cycle somewhere. */ | |
473 | ||
474 | while (pseg != 0) | |
475 | { | |
476 | #ifdef DEBUG_I00AFUNC | |
477 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
478 | #endif | |
479 | stkl = stkl - pseg; | |
480 | ssptr = (struct stack_segment_linkage *) stkl; | |
481 | size = ssptr->sssize; | |
482 | pseg = ssptr->sspseg; | |
483 | result += size; | |
484 | } | |
485 | return (result); | |
486 | } | |
487 | ||
488 | #endif /* not CRAY2 */ | |
489 | #endif /* CRAY */ | |
490 | ||
491 | #endif /* no alloca */ | |
492 | #endif /* not GCC version 2 */ | |
89e00824 ML |
493 | |
494 | /* | |
495 | Local Variables: | |
496 | c-file-style: "gnu" | |
497 | End: | |
498 | */ |