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 GB |
24 | /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999, |
25 | gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */ | |
26 | ||
2b6b80bc | 27 | #ifdef HAVE_CONFIG_H |
5ac58d89 | 28 | #include <scmconfig.h> |
2b6b80bc JB |
29 | #endif |
30 | ||
31 | #ifdef HAVE_STRING_H | |
32 | #include <string.h> | |
33 | #endif | |
34 | #ifdef HAVE_STDLIB_H | |
35 | #include <stdlib.h> | |
36 | #endif | |
37 | ||
38 | #ifdef emacs | |
39 | #include "blockinput.h" | |
40 | #endif | |
41 | ||
42 | /* If compiling with GCC 2, this file's not needed. */ | |
43 | #if !defined (__GNUC__) || __GNUC__ < 2 | |
44 | ||
45 | /* If someone has defined alloca as a macro, | |
46 | there must be some other way alloca is supposed to work. */ | |
47 | #ifndef alloca | |
48 | ||
49 | #ifdef emacs | |
50 | #ifdef static | |
51 | /* actually, only want this if static is defined as "" | |
52 | -- this is for usg, in which emacs must undefine static | |
53 | in order to make unexec workable | |
54 | */ | |
55 | #ifndef STACK_DIRECTION | |
56 | you | |
57 | lose | |
58 | -- must know STACK_DIRECTION at compile-time | |
59 | #endif /* STACK_DIRECTION undefined */ | |
60 | #endif /* static */ | |
61 | #endif /* emacs */ | |
62 | ||
63 | /* If your stack is a linked list of frames, you have to | |
64 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
65 | ||
66 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
67 | long i00afunc (); | |
68 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | |
69 | #else | |
70 | #define ADDRESS_FUNCTION(arg) &(arg) | |
71 | #endif | |
72 | ||
73 | #if __STDC__ | |
74 | typedef void *pointer; | |
75 | #else | |
76 | typedef char *pointer; | |
77 | #endif | |
78 | ||
79 | #ifndef NULL | |
80 | #define NULL 0 | |
81 | #endif | |
82 | ||
2b6b80bc JB |
83 | /* Define STACK_DIRECTION if you know the direction of stack |
84 | growth for your system; otherwise it will be automatically | |
85 | deduced at run-time. | |
86 | ||
87 | STACK_DIRECTION > 0 => grows toward higher addresses | |
88 | STACK_DIRECTION < 0 => grows toward lower addresses | |
89 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
90 | ||
91 | #ifndef STACK_DIRECTION | |
92 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
93 | #endif | |
94 | ||
95 | #if STACK_DIRECTION != 0 | |
96 | ||
97 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
98 | ||
99 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
100 | ||
101 | static int stack_dir; /* 1 or -1 once known. */ | |
102 | #define STACK_DIR stack_dir | |
103 | ||
104 | static void | |
105 | find_stack_direction () | |
106 | { | |
107 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
108 | auto char dummy; /* To get stack address. */ | |
109 | ||
110 | if (addr == NULL) | |
111 | { /* Initial entry. */ | |
112 | addr = ADDRESS_FUNCTION (dummy); | |
113 | ||
114 | find_stack_direction (); /* Recurse once. */ | |
115 | } | |
116 | else | |
117 | { | |
118 | /* Second entry. */ | |
119 | if (ADDRESS_FUNCTION (dummy) > addr) | |
120 | stack_dir = 1; /* Stack grew upward. */ | |
121 | else | |
122 | stack_dir = -1; /* Stack grew downward. */ | |
123 | } | |
124 | } | |
125 | ||
126 | #endif /* STACK_DIRECTION == 0 */ | |
127 | ||
128 | /* An "alloca header" is used to: | |
129 | (a) chain together all alloca'ed blocks; | |
130 | (b) keep track of stack depth. | |
131 | ||
132 | It is very important that sizeof(header) agree with malloc | |
133 | alignment chunk size. The following default should work okay. */ | |
134 | ||
135 | #ifndef ALIGN_SIZE | |
136 | #define ALIGN_SIZE sizeof(double) | |
137 | #endif | |
138 | ||
139 | typedef union hdr | |
140 | { | |
141 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
142 | struct | |
143 | { | |
144 | union hdr *next; /* For chaining headers. */ | |
145 | char *deep; /* For stack depth measure. */ | |
146 | } h; | |
147 | } header; | |
148 | ||
149 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
150 | ||
151 | /* Return a pointer to at least SIZE bytes of storage, | |
152 | which will be automatically reclaimed upon exit from | |
153 | the procedure that called alloca. Originally, this space | |
154 | was supposed to be taken from the current stack frame of the | |
155 | caller, but that method cannot be made to work for some | |
156 | implementations of C, for example under Gould's UTX/32. */ | |
157 | ||
158 | pointer | |
6e8d25a6 | 159 | alloca (unsigned size) |
2b6b80bc JB |
160 | { |
161 | auto char probe; /* Probes stack depth: */ | |
162 | register char *depth = ADDRESS_FUNCTION (probe); | |
163 | ||
164 | #if STACK_DIRECTION == 0 | |
165 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
166 | find_stack_direction (); | |
167 | #endif | |
168 | ||
169 | /* Reclaim garbage, defined as all alloca'd storage that | |
170 | was allocated from deeper in the stack than currently. */ | |
171 | ||
172 | { | |
173 | register header *hp; /* Traverses linked list. */ | |
174 | ||
175 | #ifdef emacs | |
176 | BLOCK_INPUT; | |
177 | #endif | |
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 | #ifdef emacs | |
195 | UNBLOCK_INPUT; | |
196 | #endif | |
197 | } | |
198 | ||
199 | if (size == 0) | |
200 | return NULL; /* No allocation required. */ | |
201 | ||
202 | /* Allocate combined header + user data storage. */ | |
203 | ||
204 | { | |
a0a06f41 | 205 | register pointer new = (pointer) malloc (sizeof (header) + size); |
2b6b80bc JB |
206 | /* Address of header. */ |
207 | ||
208 | if (new == 0) | |
f122e56e JB |
209 | { |
210 | write (2, "alloca emulation: out of memory\n", 32); | |
211 | abort(); | |
212 | } | |
2b6b80bc JB |
213 | |
214 | ((header *) new)->h.next = last_alloca_header; | |
215 | ((header *) new)->h.deep = depth; | |
216 | ||
217 | last_alloca_header = (header *) new; | |
218 | ||
219 | /* User storage begins just after header. */ | |
220 | ||
221 | return (pointer) ((char *) new + sizeof (header)); | |
222 | } | |
223 | } | |
224 | ||
225 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
226 | ||
227 | #ifdef DEBUG_I00AFUNC | |
228 | #include <stdio.h> | |
229 | #endif | |
230 | ||
231 | #ifndef CRAY_STACK | |
232 | #define CRAY_STACK | |
233 | #ifndef CRAY2 | |
234 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
235 | struct stack_control_header | |
236 | { | |
237 | long shgrow:32; /* Number of times stack has grown. */ | |
238 | long shaseg:32; /* Size of increments to stack. */ | |
239 | long shhwm:32; /* High water mark of stack. */ | |
240 | long shsize:32; /* Current size of stack (all segments). */ | |
241 | }; | |
242 | ||
243 | /* The stack segment linkage control information occurs at | |
244 | the high-address end of a stack segment. (The stack | |
245 | grows from low addresses to high addresses.) The initial | |
246 | part of the stack segment linkage control information is | |
247 | 0200 (octal) words. This provides for register storage | |
248 | for the routine which overflows the stack. */ | |
249 | ||
250 | struct stack_segment_linkage | |
251 | { | |
252 | long ss[0200]; /* 0200 overflow words. */ | |
253 | long sssize:32; /* Number of words in this segment. */ | |
254 | long ssbase:32; /* Offset to stack base. */ | |
255 | long:32; | |
256 | long sspseg:32; /* Offset to linkage control of previous | |
257 | segment of stack. */ | |
258 | long:32; | |
259 | long sstcpt:32; /* Pointer to task common address block. */ | |
260 | long sscsnm; /* Private control structure number for | |
261 | microtasking. */ | |
262 | long ssusr1; /* Reserved for user. */ | |
263 | long ssusr2; /* Reserved for user. */ | |
264 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
265 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
266 | long sscray[7]; /* Reserved for Cray Research. */ | |
267 | long ssa0; | |
268 | long ssa1; | |
269 | long ssa2; | |
270 | long ssa3; | |
271 | long ssa4; | |
272 | long ssa5; | |
273 | long ssa6; | |
274 | long ssa7; | |
275 | long sss0; | |
276 | long sss1; | |
277 | long sss2; | |
278 | long sss3; | |
279 | long sss4; | |
280 | long sss5; | |
281 | long sss6; | |
282 | long sss7; | |
283 | }; | |
284 | ||
285 | #else /* CRAY2 */ | |
286 | /* The following structure defines the vector of words | |
287 | returned by the STKSTAT library routine. */ | |
288 | struct stk_stat | |
289 | { | |
290 | long now; /* Current total stack size. */ | |
291 | long maxc; /* Amount of contiguous space which would | |
292 | be required to satisfy the maximum | |
293 | stack demand to date. */ | |
294 | long high_water; /* Stack high-water mark. */ | |
295 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
296 | long hits; /* Number of internal buffer hits. */ | |
297 | long extends; /* Number of block extensions. */ | |
298 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
299 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
300 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
301 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
302 | long segments; /* Current number of stack segments. */ | |
303 | long maxs; /* Maximum number of stack segments so far. */ | |
304 | long pad_size; /* Stack pad size. */ | |
305 | long current_address; /* Current stack segment address. */ | |
306 | long current_size; /* Current stack segment size. This | |
307 | number is actually corrupted by STKSTAT to | |
308 | include the fifteen word trailer area. */ | |
309 | long initial_address; /* Address of initial segment. */ | |
310 | long initial_size; /* Size of initial segment. */ | |
311 | }; | |
312 | ||
313 | /* The following structure describes the data structure which trails | |
314 | any stack segment. I think that the description in 'asdef' is | |
315 | out of date. I only describe the parts that I am sure about. */ | |
316 | ||
317 | struct stk_trailer | |
318 | { | |
319 | long this_address; /* Address of this block. */ | |
320 | long this_size; /* Size of this block (does not include | |
321 | this trailer). */ | |
322 | long unknown2; | |
323 | long unknown3; | |
324 | long link; /* Address of trailer block of previous | |
325 | segment. */ | |
326 | long unknown5; | |
327 | long unknown6; | |
328 | long unknown7; | |
329 | long unknown8; | |
330 | long unknown9; | |
331 | long unknown10; | |
332 | long unknown11; | |
333 | long unknown12; | |
334 | long unknown13; | |
335 | long unknown14; | |
336 | }; | |
337 | ||
338 | #endif /* CRAY2 */ | |
339 | #endif /* not CRAY_STACK */ | |
340 | ||
341 | #ifdef CRAY2 | |
342 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
343 | I doubt that "lint" will like this much. */ | |
344 | ||
345 | static long | |
346 | i00afunc (long *address) | |
347 | { | |
348 | struct stk_stat status; | |
349 | struct stk_trailer *trailer; | |
350 | long *block, size; | |
351 | long result = 0; | |
352 | ||
353 | /* We want to iterate through all of the segments. The first | |
354 | step is to get the stack status structure. We could do this | |
355 | more quickly and more directly, perhaps, by referencing the | |
356 | $LM00 common block, but I know that this works. */ | |
357 | ||
358 | STKSTAT (&status); | |
359 | ||
360 | /* Set up the iteration. */ | |
361 | ||
362 | trailer = (struct stk_trailer *) (status.current_address | |
363 | + status.current_size | |
364 | - 15); | |
365 | ||
366 | /* There must be at least one stack segment. Therefore it is | |
367 | a fatal error if "trailer" is null. */ | |
368 | ||
369 | if (trailer == 0) | |
370 | abort (); | |
371 | ||
372 | /* Discard segments that do not contain our argument address. */ | |
373 | ||
374 | while (trailer != 0) | |
375 | { | |
376 | block = (long *) trailer->this_address; | |
377 | size = trailer->this_size; | |
378 | if (block == 0 || size == 0) | |
379 | abort (); | |
380 | trailer = (struct stk_trailer *) trailer->link; | |
381 | if ((block <= address) && (address < (block + size))) | |
382 | break; | |
383 | } | |
384 | ||
385 | /* Set the result to the offset in this segment and add the sizes | |
386 | of all predecessor segments. */ | |
387 | ||
388 | result = address - block; | |
389 | ||
390 | if (trailer == 0) | |
391 | { | |
392 | return result; | |
393 | } | |
394 | ||
395 | do | |
396 | { | |
397 | if (trailer->this_size <= 0) | |
398 | abort (); | |
399 | result += trailer->this_size; | |
400 | trailer = (struct stk_trailer *) trailer->link; | |
401 | } | |
402 | while (trailer != 0); | |
403 | ||
404 | /* We are done. Note that if you present a bogus address (one | |
405 | not in any segment), you will get a different number back, formed | |
406 | from subtracting the address of the first block. This is probably | |
407 | not what you want. */ | |
408 | ||
409 | return (result); | |
410 | } | |
411 | ||
412 | #else /* not CRAY2 */ | |
413 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
414 | Determine the number of the cell within the stack, | |
415 | given the address of the cell. The purpose of this | |
416 | routine is to linearize, in some sense, stack addresses | |
417 | for alloca. */ | |
418 | ||
419 | static long | |
420 | i00afunc (long address) | |
421 | { | |
422 | long stkl = 0; | |
423 | ||
424 | long size, pseg, this_segment, stack; | |
425 | long result = 0; | |
426 | ||
427 | struct stack_segment_linkage *ssptr; | |
428 | ||
429 | /* Register B67 contains the address of the end of the | |
430 | current stack segment. If you (as a subprogram) store | |
431 | your registers on the stack and find that you are past | |
432 | the contents of B67, you have overflowed the segment. | |
433 | ||
434 | B67 also points to the stack segment linkage control | |
435 | area, which is what we are really interested in. */ | |
436 | ||
437 | stkl = CRAY_STACKSEG_END (); | |
438 | ssptr = (struct stack_segment_linkage *) stkl; | |
439 | ||
440 | /* If one subtracts 'size' from the end of the segment, | |
441 | one has the address of the first word of the segment. | |
442 | ||
443 | If this is not the first segment, 'pseg' will be | |
444 | nonzero. */ | |
445 | ||
446 | pseg = ssptr->sspseg; | |
447 | size = ssptr->sssize; | |
448 | ||
449 | this_segment = stkl - size; | |
450 | ||
451 | /* It is possible that calling this routine itself caused | |
452 | a stack overflow. Discard stack segments which do not | |
453 | contain the target address. */ | |
454 | ||
455 | while (!(this_segment <= address && address <= stkl)) | |
456 | { | |
457 | #ifdef DEBUG_I00AFUNC | |
458 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
459 | #endif | |
460 | if (pseg == 0) | |
461 | break; | |
462 | stkl = stkl - pseg; | |
463 | ssptr = (struct stack_segment_linkage *) stkl; | |
464 | size = ssptr->sssize; | |
465 | pseg = ssptr->sspseg; | |
466 | this_segment = stkl - size; | |
467 | } | |
468 | ||
469 | result = address - this_segment; | |
470 | ||
471 | /* If you subtract pseg from the current end of the stack, | |
472 | you get the address of the previous stack segment's end. | |
473 | This seems a little convoluted to me, but I'll bet you save | |
474 | a cycle somewhere. */ | |
475 | ||
476 | while (pseg != 0) | |
477 | { | |
478 | #ifdef DEBUG_I00AFUNC | |
479 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
480 | #endif | |
481 | stkl = stkl - pseg; | |
482 | ssptr = (struct stack_segment_linkage *) stkl; | |
483 | size = ssptr->sssize; | |
484 | pseg = ssptr->sspseg; | |
485 | result += size; | |
486 | } | |
487 | return (result); | |
488 | } | |
489 | ||
490 | #endif /* not CRAY2 */ | |
491 | #endif /* CRAY */ | |
492 | ||
493 | #endif /* no alloca */ | |
494 | #endif /* not GCC version 2 */ | |
89e00824 ML |
495 | |
496 | /* | |
497 | Local Variables: | |
498 | c-file-style: "gnu" | |
499 | End: | |
500 | */ |