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252b5132 RH |
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 | |
25 | #include <config.h> | |
26 | #endif | |
27 | ||
30673bf5 DD |
28 | #include <libiberty.h> |
29 | ||
252b5132 RH |
30 | #ifdef HAVE_STRING_H |
31 | #include <string.h> | |
32 | #endif | |
33 | #ifdef HAVE_STDLIB_H | |
34 | #include <stdlib.h> | |
35 | #endif | |
36 | ||
252b5132 RH |
37 | /* If your stack is a linked list of frames, you have to |
38 | provide an "address metric" ADDRESS_FUNCTION macro. */ | |
39 | ||
40 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
30673bf5 | 41 | static long i00afunc (); |
252b5132 RH |
42 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) |
43 | #else | |
44 | #define ADDRESS_FUNCTION(arg) &(arg) | |
45 | #endif | |
46 | ||
252b5132 RH |
47 | #ifndef NULL |
48 | #define NULL 0 | |
49 | #endif | |
50 | ||
252b5132 RH |
51 | /* Define STACK_DIRECTION if you know the direction of stack |
52 | growth for your system; otherwise it will be automatically | |
53 | deduced at run-time. | |
54 | ||
55 | STACK_DIRECTION > 0 => grows toward higher addresses | |
56 | STACK_DIRECTION < 0 => grows toward lower addresses | |
57 | STACK_DIRECTION = 0 => direction of growth unknown */ | |
58 | ||
59 | #ifndef STACK_DIRECTION | |
60 | #define STACK_DIRECTION 0 /* Direction unknown. */ | |
61 | #endif | |
62 | ||
63 | #if STACK_DIRECTION != 0 | |
64 | ||
65 | #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */ | |
66 | ||
67 | #else /* STACK_DIRECTION == 0; need run-time code. */ | |
68 | ||
69 | static int stack_dir; /* 1 or -1 once known. */ | |
70 | #define STACK_DIR stack_dir | |
71 | ||
72 | static void | |
73 | find_stack_direction () | |
74 | { | |
75 | static char *addr = NULL; /* Address of first `dummy', once known. */ | |
76 | auto char dummy; /* To get stack address. */ | |
77 | ||
78 | if (addr == NULL) | |
79 | { /* Initial entry. */ | |
80 | addr = ADDRESS_FUNCTION (dummy); | |
81 | ||
82 | find_stack_direction (); /* Recurse once. */ | |
83 | } | |
84 | else | |
85 | { | |
86 | /* Second entry. */ | |
87 | if (ADDRESS_FUNCTION (dummy) > addr) | |
88 | stack_dir = 1; /* Stack grew upward. */ | |
89 | else | |
90 | stack_dir = -1; /* Stack grew downward. */ | |
91 | } | |
92 | } | |
93 | ||
94 | #endif /* STACK_DIRECTION == 0 */ | |
95 | ||
96 | /* An "alloca header" is used to: | |
97 | (a) chain together all alloca'ed blocks; | |
98 | (b) keep track of stack depth. | |
99 | ||
100 | It is very important that sizeof(header) agree with malloc | |
101 | alignment chunk size. The following default should work okay. */ | |
102 | ||
103 | #ifndef ALIGN_SIZE | |
104 | #define ALIGN_SIZE sizeof(double) | |
105 | #endif | |
106 | ||
107 | typedef union hdr | |
108 | { | |
109 | char align[ALIGN_SIZE]; /* To force sizeof(header). */ | |
110 | struct | |
111 | { | |
112 | union hdr *next; /* For chaining headers. */ | |
113 | char *deep; /* For stack depth measure. */ | |
114 | } h; | |
115 | } header; | |
116 | ||
117 | static header *last_alloca_header = NULL; /* -> last alloca header. */ | |
118 | ||
119 | /* Return a pointer to at least SIZE bytes of storage, | |
120 | which will be automatically reclaimed upon exit from | |
121 | the procedure that called alloca. Originally, this space | |
122 | was supposed to be taken from the current stack frame of the | |
123 | caller, but that method cannot be made to work for some | |
124 | implementations of C, for example under Gould's UTX/32. */ | |
125 | ||
30673bf5 DD |
126 | PTR |
127 | C_alloca (size) | |
128 | size_t size; | |
252b5132 RH |
129 | { |
130 | auto char probe; /* Probes stack depth: */ | |
131 | register char *depth = ADDRESS_FUNCTION (probe); | |
132 | ||
133 | #if STACK_DIRECTION == 0 | |
134 | if (STACK_DIR == 0) /* Unknown growth direction. */ | |
135 | find_stack_direction (); | |
136 | #endif | |
137 | ||
138 | /* Reclaim garbage, defined as all alloca'd storage that | |
139 | was allocated from deeper in the stack than currently. */ | |
140 | ||
141 | { | |
142 | register header *hp; /* Traverses linked list. */ | |
143 | ||
252b5132 RH |
144 | for (hp = last_alloca_header; hp != NULL;) |
145 | if ((STACK_DIR > 0 && hp->h.deep > depth) | |
146 | || (STACK_DIR < 0 && hp->h.deep < depth)) | |
147 | { | |
148 | register header *np = hp->h.next; | |
149 | ||
30673bf5 | 150 | free ((PTR) hp); /* Collect garbage. */ |
252b5132 RH |
151 | |
152 | hp = np; /* -> next header. */ | |
153 | } | |
154 | else | |
155 | break; /* Rest are not deeper. */ | |
156 | ||
157 | last_alloca_header = hp; /* -> last valid storage. */ | |
252b5132 RH |
158 | } |
159 | ||
160 | if (size == 0) | |
161 | return NULL; /* No allocation required. */ | |
162 | ||
163 | /* Allocate combined header + user data storage. */ | |
164 | ||
165 | { | |
30673bf5 | 166 | register PTR new = xmalloc (sizeof (header) + size); |
252b5132 RH |
167 | /* Address of header. */ |
168 | ||
169 | if (new == 0) | |
170 | abort(); | |
171 | ||
172 | ((header *) new)->h.next = last_alloca_header; | |
173 | ((header *) new)->h.deep = depth; | |
174 | ||
175 | last_alloca_header = (header *) new; | |
176 | ||
177 | /* User storage begins just after header. */ | |
178 | ||
30673bf5 | 179 | return (PTR) ((char *) new + sizeof (header)); |
252b5132 RH |
180 | } |
181 | } | |
182 | ||
183 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | |
184 | ||
185 | #ifdef DEBUG_I00AFUNC | |
186 | #include <stdio.h> | |
187 | #endif | |
188 | ||
189 | #ifndef CRAY_STACK | |
190 | #define CRAY_STACK | |
191 | #ifndef CRAY2 | |
192 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | |
193 | struct stack_control_header | |
194 | { | |
195 | long shgrow:32; /* Number of times stack has grown. */ | |
196 | long shaseg:32; /* Size of increments to stack. */ | |
197 | long shhwm:32; /* High water mark of stack. */ | |
198 | long shsize:32; /* Current size of stack (all segments). */ | |
199 | }; | |
200 | ||
201 | /* The stack segment linkage control information occurs at | |
202 | the high-address end of a stack segment. (The stack | |
203 | grows from low addresses to high addresses.) The initial | |
204 | part of the stack segment linkage control information is | |
205 | 0200 (octal) words. This provides for register storage | |
206 | for the routine which overflows the stack. */ | |
207 | ||
208 | struct stack_segment_linkage | |
209 | { | |
210 | long ss[0200]; /* 0200 overflow words. */ | |
211 | long sssize:32; /* Number of words in this segment. */ | |
212 | long ssbase:32; /* Offset to stack base. */ | |
213 | long:32; | |
214 | long sspseg:32; /* Offset to linkage control of previous | |
215 | segment of stack. */ | |
216 | long:32; | |
217 | long sstcpt:32; /* Pointer to task common address block. */ | |
218 | long sscsnm; /* Private control structure number for | |
219 | microtasking. */ | |
220 | long ssusr1; /* Reserved for user. */ | |
221 | long ssusr2; /* Reserved for user. */ | |
222 | long sstpid; /* Process ID for pid based multi-tasking. */ | |
223 | long ssgvup; /* Pointer to multitasking thread giveup. */ | |
224 | long sscray[7]; /* Reserved for Cray Research. */ | |
225 | long ssa0; | |
226 | long ssa1; | |
227 | long ssa2; | |
228 | long ssa3; | |
229 | long ssa4; | |
230 | long ssa5; | |
231 | long ssa6; | |
232 | long ssa7; | |
233 | long sss0; | |
234 | long sss1; | |
235 | long sss2; | |
236 | long sss3; | |
237 | long sss4; | |
238 | long sss5; | |
239 | long sss6; | |
240 | long sss7; | |
241 | }; | |
242 | ||
243 | #else /* CRAY2 */ | |
244 | /* The following structure defines the vector of words | |
245 | returned by the STKSTAT library routine. */ | |
246 | struct stk_stat | |
247 | { | |
248 | long now; /* Current total stack size. */ | |
249 | long maxc; /* Amount of contiguous space which would | |
250 | be required to satisfy the maximum | |
251 | stack demand to date. */ | |
252 | long high_water; /* Stack high-water mark. */ | |
253 | long overflows; /* Number of stack overflow ($STKOFEN) calls. */ | |
254 | long hits; /* Number of internal buffer hits. */ | |
255 | long extends; /* Number of block extensions. */ | |
256 | long stko_mallocs; /* Block allocations by $STKOFEN. */ | |
257 | long underflows; /* Number of stack underflow calls ($STKRETN). */ | |
258 | long stko_free; /* Number of deallocations by $STKRETN. */ | |
259 | long stkm_free; /* Number of deallocations by $STKMRET. */ | |
260 | long segments; /* Current number of stack segments. */ | |
261 | long maxs; /* Maximum number of stack segments so far. */ | |
262 | long pad_size; /* Stack pad size. */ | |
263 | long current_address; /* Current stack segment address. */ | |
264 | long current_size; /* Current stack segment size. This | |
265 | number is actually corrupted by STKSTAT to | |
266 | include the fifteen word trailer area. */ | |
267 | long initial_address; /* Address of initial segment. */ | |
268 | long initial_size; /* Size of initial segment. */ | |
269 | }; | |
270 | ||
271 | /* The following structure describes the data structure which trails | |
272 | any stack segment. I think that the description in 'asdef' is | |
273 | out of date. I only describe the parts that I am sure about. */ | |
274 | ||
275 | struct stk_trailer | |
276 | { | |
277 | long this_address; /* Address of this block. */ | |
278 | long this_size; /* Size of this block (does not include | |
279 | this trailer). */ | |
280 | long unknown2; | |
281 | long unknown3; | |
282 | long link; /* Address of trailer block of previous | |
283 | segment. */ | |
284 | long unknown5; | |
285 | long unknown6; | |
286 | long unknown7; | |
287 | long unknown8; | |
288 | long unknown9; | |
289 | long unknown10; | |
290 | long unknown11; | |
291 | long unknown12; | |
292 | long unknown13; | |
293 | long unknown14; | |
294 | }; | |
295 | ||
296 | #endif /* CRAY2 */ | |
297 | #endif /* not CRAY_STACK */ | |
298 | ||
299 | #ifdef CRAY2 | |
300 | /* Determine a "stack measure" for an arbitrary ADDRESS. | |
301 | I doubt that "lint" will like this much. */ | |
302 | ||
303 | static long | |
304 | i00afunc (long *address) | |
305 | { | |
306 | struct stk_stat status; | |
307 | struct stk_trailer *trailer; | |
308 | long *block, size; | |
309 | long result = 0; | |
310 | ||
311 | /* We want to iterate through all of the segments. The first | |
312 | step is to get the stack status structure. We could do this | |
313 | more quickly and more directly, perhaps, by referencing the | |
314 | $LM00 common block, but I know that this works. */ | |
315 | ||
316 | STKSTAT (&status); | |
317 | ||
318 | /* Set up the iteration. */ | |
319 | ||
320 | trailer = (struct stk_trailer *) (status.current_address | |
321 | + status.current_size | |
322 | - 15); | |
323 | ||
324 | /* There must be at least one stack segment. Therefore it is | |
325 | a fatal error if "trailer" is null. */ | |
326 | ||
327 | if (trailer == 0) | |
328 | abort (); | |
329 | ||
330 | /* Discard segments that do not contain our argument address. */ | |
331 | ||
332 | while (trailer != 0) | |
333 | { | |
334 | block = (long *) trailer->this_address; | |
335 | size = trailer->this_size; | |
336 | if (block == 0 || size == 0) | |
337 | abort (); | |
338 | trailer = (struct stk_trailer *) trailer->link; | |
339 | if ((block <= address) && (address < (block + size))) | |
340 | break; | |
341 | } | |
342 | ||
343 | /* Set the result to the offset in this segment and add the sizes | |
344 | of all predecessor segments. */ | |
345 | ||
346 | result = address - block; | |
347 | ||
348 | if (trailer == 0) | |
349 | { | |
350 | return result; | |
351 | } | |
352 | ||
353 | do | |
354 | { | |
355 | if (trailer->this_size <= 0) | |
356 | abort (); | |
357 | result += trailer->this_size; | |
358 | trailer = (struct stk_trailer *) trailer->link; | |
359 | } | |
360 | while (trailer != 0); | |
361 | ||
362 | /* We are done. Note that if you present a bogus address (one | |
363 | not in any segment), you will get a different number back, formed | |
364 | from subtracting the address of the first block. This is probably | |
365 | not what you want. */ | |
366 | ||
367 | return (result); | |
368 | } | |
369 | ||
370 | #else /* not CRAY2 */ | |
371 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | |
372 | Determine the number of the cell within the stack, | |
373 | given the address of the cell. The purpose of this | |
374 | routine is to linearize, in some sense, stack addresses | |
375 | for alloca. */ | |
376 | ||
377 | static long | |
378 | i00afunc (long address) | |
379 | { | |
380 | long stkl = 0; | |
381 | ||
382 | long size, pseg, this_segment, stack; | |
383 | long result = 0; | |
384 | ||
385 | struct stack_segment_linkage *ssptr; | |
386 | ||
387 | /* Register B67 contains the address of the end of the | |
388 | current stack segment. If you (as a subprogram) store | |
389 | your registers on the stack and find that you are past | |
390 | the contents of B67, you have overflowed the segment. | |
391 | ||
392 | B67 also points to the stack segment linkage control | |
393 | area, which is what we are really interested in. */ | |
394 | ||
395 | stkl = CRAY_STACKSEG_END (); | |
396 | ssptr = (struct stack_segment_linkage *) stkl; | |
397 | ||
398 | /* If one subtracts 'size' from the end of the segment, | |
399 | one has the address of the first word of the segment. | |
400 | ||
401 | If this is not the first segment, 'pseg' will be | |
402 | nonzero. */ | |
403 | ||
404 | pseg = ssptr->sspseg; | |
405 | size = ssptr->sssize; | |
406 | ||
407 | this_segment = stkl - size; | |
408 | ||
409 | /* It is possible that calling this routine itself caused | |
410 | a stack overflow. Discard stack segments which do not | |
411 | contain the target address. */ | |
412 | ||
413 | while (!(this_segment <= address && address <= stkl)) | |
414 | { | |
415 | #ifdef DEBUG_I00AFUNC | |
416 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | |
417 | #endif | |
418 | if (pseg == 0) | |
419 | break; | |
420 | stkl = stkl - pseg; | |
421 | ssptr = (struct stack_segment_linkage *) stkl; | |
422 | size = ssptr->sssize; | |
423 | pseg = ssptr->sspseg; | |
424 | this_segment = stkl - size; | |
425 | } | |
426 | ||
427 | result = address - this_segment; | |
428 | ||
429 | /* If you subtract pseg from the current end of the stack, | |
430 | you get the address of the previous stack segment's end. | |
431 | This seems a little convoluted to me, but I'll bet you save | |
432 | a cycle somewhere. */ | |
433 | ||
434 | while (pseg != 0) | |
435 | { | |
436 | #ifdef DEBUG_I00AFUNC | |
437 | fprintf (stderr, "%011o %011o\n", pseg, size); | |
438 | #endif | |
439 | stkl = stkl - pseg; | |
440 | ssptr = (struct stack_segment_linkage *) stkl; | |
441 | size = ssptr->sssize; | |
442 | pseg = ssptr->sspseg; | |
443 | result += size; | |
444 | } | |
445 | return (result); | |
446 | } | |
447 | ||
448 | #endif /* not CRAY2 */ | |
449 | #endif /* CRAY */ |