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428
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1 /* alloca.c -- allocate automatically reclaimed memory
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2 (Mostly) portable public-domain implementation -- D A Gwyn
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3
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4 This implementation of the PWB library alloca function,
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5 which is used to allocate space off the run-time stack so
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6 that it is automatically reclaimed upon procedure exit,
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7 was inspired by discussions with J. Q. Johnson of Cornell.
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8 J.Otto Tennant <jot@cray.com> contributed the Cray support.
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9
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10 There are some preprocessor constants that can
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11 be defined when compiling for your specific system, for
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12 improved efficiency; however, the defaults should be okay.
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13
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14 The general concept of this implementation is to keep
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15 track of all alloca-allocated blocks, and reclaim any
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16 that are found to be deeper in the stack than the current
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17 invocation. This heuristic does not reclaim storage as
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18 soon as it becomes invalid, but it will do so eventually.
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19
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20 As a special case, alloca(0) reclaims storage without
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21 allocating any. It is a good idea to use alloca(0) in
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22 your main control loop, etc. to force garbage collection. */
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23
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24 /* Synched up with: FSF 19.30. */
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25
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442
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26 /* Authorship:
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428
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27
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28 FSF: A long time ago.
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851
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29 Some cleanups for XEmacs.
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428
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30 */
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31
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32 #ifdef HAVE_CONFIG_H
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33 #include <config.h>
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34 #endif
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35
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36 #ifdef emacs
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851
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37 #include "lisp.h"
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38 #endif
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428
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39
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40 /* If your stack is a linked list of frames, you have to
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41 provide an "address metric" ADDRESS_FUNCTION macro. */
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42
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43 #if defined (CRAY) && defined (CRAY_STACKSEG_END)
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44 long i00afunc ();
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45 #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg))
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46 #else
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47 #define ADDRESS_FUNCTION(arg) &(arg)
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48 #endif
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49
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50 typedef void *pointer;
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51
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442
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52 #ifndef NULL
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428
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53 #define NULL 0
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54 #endif
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55
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56 /* Define STACK_DIRECTION if you know the direction of stack
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57 growth for your system; otherwise it will be automatically
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58 deduced at run-time.
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59
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60 STACK_DIRECTION > 0 => grows toward higher addresses
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61 STACK_DIRECTION < 0 => grows toward lower addresses
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62 STACK_DIRECTION = 0 => direction of growth unknown */
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63
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64 #ifndef STACK_DIRECTION
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65 #define STACK_DIRECTION 0 /* Direction unknown. */
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66 #endif
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67
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68 #if STACK_DIRECTION != 0
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69
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70 #define STACK_DIR STACK_DIRECTION /* Known at compile-time. */
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71
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72 #else /* STACK_DIRECTION == 0; need run-time code. */
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73
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74 static int stack_dir; /* 1 or -1 once known. */
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75 #define STACK_DIR stack_dir
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76
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77 static void
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1111
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78 find_stack_direction (void)
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428
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79 {
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80 static char *addr = NULL; /* Address of first `dummy', once known. */
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81 auto char dummy; /* To get stack address. */
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82
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83 if (addr == NULL)
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84 { /* Initial entry. */
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85 addr = ADDRESS_FUNCTION (dummy);
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86
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87 find_stack_direction (); /* Recurse once. */
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88 }
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89 else
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90 {
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91 /* Second entry. */
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92 if (ADDRESS_FUNCTION (dummy) > addr)
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93 stack_dir = 1; /* Stack grew upward. */
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94 else
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95 stack_dir = -1; /* Stack grew downward. */
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96 }
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97 }
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98
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99 #endif /* STACK_DIRECTION == 0 */
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100
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101 /* An "alloca header" is used to:
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102 (a) chain together all alloca'ed blocks;
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103 (b) keep track of stack depth.
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104
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105 It is very important that sizeof(header) agree with malloc
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106 alignment chunk size. The following default should work okay. */
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107
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|
851
|
108 #ifndef ALIGNMENT_SIZE
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109 #define ALIGNMENT_SIZE sizeof(double)
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428
|
110 #endif
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111
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112 typedef union hdr
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113 {
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851
|
114 char align[ALIGNMENT_SIZE]; /* To force sizeof(header). */
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428
|
115 struct
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116 {
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117 union hdr *next; /* For chaining headers. */
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118 char *deep; /* For stack depth measure. */
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119 } h;
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120 } header;
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121
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122 static header *last_alloca_header = NULL; /* -> last alloca header. */
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123
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124 /* Return a pointer to at least SIZE bytes of storage,
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125 which will be automatically reclaimed upon exit from
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126 the procedure that called alloca. Originally, this space
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127 was supposed to be taken from the current stack frame of the
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128 caller, but that method cannot be made to work for some
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129 implementations of C, for example under Gould's UTX/32. */
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130
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131 pointer
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|
851
|
132 xemacs_c_alloca (unsigned int size)
|
|
428
|
133 {
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134 auto char probe; /* Probes stack depth: */
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442
|
135 register char *depth = ADDRESS_FUNCTION (probe);
|
|
428
|
136
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137 #if STACK_DIRECTION == 0
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|
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138 if (STACK_DIR == 0) /* Unknown growth direction. */
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139 find_stack_direction ();
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140 #endif
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141
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|
142 /* Reclaim garbage, defined as all alloca'd storage that
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143 was allocated from deeper in the stack than currently. */
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144
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|
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145 {
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442
|
146 register header *hp; /* Traverses linked list. */
|
|
428
|
147
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|
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148 for (hp = last_alloca_header; hp != NULL;)
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|
149 if ((STACK_DIR > 0 && hp->h.deep > depth)
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|
150 || (STACK_DIR < 0 && hp->h.deep < depth))
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|
|
151 {
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|
442
|
152 register header *np = hp->h.next;
|
|
428
|
153
|
|
851
|
154 #ifdef emacs
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|
1726
|
155 xfree (hp, header *); /* Collect garbage. */
|
|
851
|
156 #else
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|
|
157 free (hp); /* Collect garbage. */
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|
|
158 #endif
|
|
428
|
159
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|
|
160 hp = np; /* -> next header. */
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|
|
161 }
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|
|
162 else
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|
|
163 break; /* Rest are not deeper. */
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164
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|
|
165 last_alloca_header = hp; /* -> last valid storage. */
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|
|
166 }
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|
|
167
|
|
851
|
168 #ifdef emacs
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|
|
169 need_to_check_c_alloca = size > 0 || last_alloca_header;
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|
|
170 recompute_funcall_allocation_flag ();
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|
|
171 #endif
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|
|
172
|
|
428
|
173 if (size == 0)
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|
|
174 return NULL; /* No allocation required. */
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|
|
175
|
|
|
176 /* Allocate combined header + user data storage. */
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|
|
177
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|
|
178 {
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|
851
|
179 #ifdef emacs
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|
|
180 register pointer new = xmalloc (sizeof (header) + size);
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|
|
181 #else
|
|
442
|
182 register pointer new = malloc (sizeof (header) + size);
|
|
851
|
183 #endif
|
|
428
|
184 /* Address of header. */
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|
|
185
|
|
|
186 ((header *) new)->h.next = last_alloca_header;
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|
|
187 ((header *) new)->h.deep = depth;
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|
|
188
|
|
|
189 last_alloca_header = (header *) new;
|
|
|
190
|
|
|
191 /* User storage begins just after header. */
|
|
|
192
|
|
|
193 return (pointer) ((char *) new + sizeof (header));
|
|
|
194 }
|
|
|
195 }
|
|
|
196
|
|
|
197 #if defined (CRAY) && defined (CRAY_STACKSEG_END)
|
|
|
198
|
|
|
199 #ifdef DEBUG_I00AFUNC
|
|
|
200 #include <stdio.h>
|
|
|
201 #endif
|
|
|
202
|
|
|
203 #ifndef CRAY_STACK
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|
|
204 #define CRAY_STACK
|
|
|
205 #ifndef CRAY2
|
|
|
206 /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */
|
|
|
207 struct stack_control_header
|
|
|
208 {
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|
|
209 long shgrow:32; /* Number of times stack has grown. */
|
|
|
210 long shaseg:32; /* Size of increments to stack. */
|
|
|
211 long shhwm:32; /* High water mark of stack. */
|
|
|
212 long shsize:32; /* Current size of stack (all segments). */
|
|
|
213 };
|
|
|
214
|
|
|
215 /* The stack segment linkage control information occurs at
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|
|
216 the high-address end of a stack segment. (The stack
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|
|
217 grows from low addresses to high addresses.) The initial
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|
|
218 part of the stack segment linkage control information is
|
|
|
219 0200 (octal) words. This provides for register storage
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|
|
220 for the routine which overflows the stack. */
|
|
|
221
|
|
|
222 struct stack_segment_linkage
|
|
|
223 {
|
|
|
224 long ss[0200]; /* 0200 overflow words. */
|
|
|
225 long sssize:32; /* Number of words in this segment. */
|
|
|
226 long ssbase:32; /* Offset to stack base. */
|
|
|
227 long:32;
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|
|
228 long sspseg:32; /* Offset to linkage control of previous
|
|
|
229 segment of stack. */
|
|
|
230 long:32;
|
|
|
231 long sstcpt:32; /* Pointer to task common address block. */
|
|
|
232 long sscsnm; /* Private control structure number for
|
|
|
233 microtasking. */
|
|
|
234 long ssusr1; /* Reserved for user. */
|
|
|
235 long ssusr2; /* Reserved for user. */
|
|
|
236 long sstpid; /* Process ID for pid based multi-tasking. */
|
|
|
237 long ssgvup; /* Pointer to multitasking thread giveup. */
|
|
|
238 long sscray[7]; /* Reserved for Cray Research. */
|
|
|
239 long ssa0;
|
|
|
240 long ssa1;
|
|
|
241 long ssa2;
|
|
|
242 long ssa3;
|
|
|
243 long ssa4;
|
|
|
244 long ssa5;
|
|
|
245 long ssa6;
|
|
|
246 long ssa7;
|
|
|
247 long sss0;
|
|
|
248 long sss1;
|
|
|
249 long sss2;
|
|
|
250 long sss3;
|
|
|
251 long sss4;
|
|
|
252 long sss5;
|
|
|
253 long sss6;
|
|
|
254 long sss7;
|
|
|
255 };
|
|
|
256
|
|
|
257 #else /* CRAY2 */
|
|
|
258 /* The following structure defines the vector of words
|
|
|
259 returned by the STKSTAT library routine. */
|
|
|
260 struct stk_stat
|
|
|
261 {
|
|
|
262 long now; /* Current total stack size. */
|
|
|
263 long maxc; /* Amount of contiguous space which would
|
|
|
264 be required to satisfy the maximum
|
|
|
265 stack demand to date. */
|
|
|
266 long high_water; /* Stack high-water mark. */
|
|
|
267 long overflows; /* Number of stack overflow ($STKOFEN) calls. */
|
|
|
268 long hits; /* Number of internal buffer hits. */
|
|
|
269 long extends; /* Number of block extensions. */
|
|
|
270 long stko_mallocs; /* Block allocations by $STKOFEN. */
|
|
|
271 long underflows; /* Number of stack underflow calls ($STKRETN). */
|
|
|
272 long stko_free; /* Number of deallocations by $STKRETN. */
|
|
|
273 long stkm_free; /* Number of deallocations by $STKMRET. */
|
|
|
274 long segments; /* Current number of stack segments. */
|
|
|
275 long maxs; /* Maximum number of stack segments so far. */
|
|
|
276 long pad_size; /* Stack pad size. */
|
|
|
277 long current_address; /* Current stack segment address. */
|
|
|
278 long current_size; /* Current stack segment size. This
|
|
|
279 number is actually corrupted by STKSTAT to
|
|
|
280 include the fifteen word trailer area. */
|
|
|
281 long initial_address; /* Address of initial segment. */
|
|
|
282 long initial_size; /* Size of initial segment. */
|
|
|
283 };
|
|
|
284
|
|
|
285 /* The following structure describes the data structure which trails
|
|
|
286 any stack segment. I think that the description in 'asdef' is
|
|
|
287 out of date. I only describe the parts that I am sure about. */
|
|
|
288
|
|
|
289 struct stk_trailer
|
|
|
290 {
|
|
|
291 long this_address; /* Address of this block. */
|
|
|
292 long this_size; /* Size of this block (does not include
|
|
|
293 this trailer). */
|
|
|
294 long unknown2;
|
|
|
295 long unknown3;
|
|
|
296 long link; /* Address of trailer block of previous
|
|
|
297 segment. */
|
|
|
298 long unknown5;
|
|
|
299 long unknown6;
|
|
|
300 long unknown7;
|
|
|
301 long unknown8;
|
|
|
302 long unknown9;
|
|
|
303 long unknown10;
|
|
|
304 long unknown11;
|
|
|
305 long unknown12;
|
|
|
306 long unknown13;
|
|
|
307 long unknown14;
|
|
|
308 };
|
|
|
309
|
|
|
310 #endif /* CRAY2 */
|
|
|
311 #endif /* not CRAY_STACK */
|
|
|
312
|
|
|
313 #ifdef CRAY2
|
|
|
314 /* Determine a "stack measure" for an arbitrary ADDRESS.
|
|
|
315 I doubt that "lint" will like this much. */
|
|
|
316
|
|
|
317 static long
|
|
|
318 i00afunc (long *address)
|
|
|
319 {
|
|
|
320 struct stk_stat status;
|
|
|
321 struct stk_trailer *trailer;
|
|
|
322 long *block, size;
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|
|
323 long result = 0;
|
|
|
324
|
|
|
325 /* We want to iterate through all of the segments. The first
|
|
|
326 step is to get the stack status structure. We could do this
|
|
|
327 more quickly and more directly, perhaps, by referencing the
|
|
|
328 $LM00 common block, but I know that this works. */
|
|
|
329
|
|
|
330 STKSTAT (&status);
|
|
|
331
|
|
|
332 /* Set up the iteration. */
|
|
|
333
|
|
|
334 trailer = (struct stk_trailer *) (status.current_address
|
|
|
335 + status.current_size
|
|
|
336 - 15);
|
|
|
337
|
|
|
338 /* There must be at least one stack segment. Therefore it is
|
|
|
339 a fatal error if "trailer" is null. */
|
|
|
340
|
|
|
341 if (trailer == 0)
|
|
|
342 abort ();
|
|
|
343
|
|
|
344 /* Discard segments that do not contain our argument address. */
|
|
|
345
|
|
|
346 while (trailer != 0)
|
|
|
347 {
|
|
|
348 block = (long *) trailer->this_address;
|
|
|
349 size = trailer->this_size;
|
|
|
350 if (block == 0 || size == 0)
|
|
|
351 abort ();
|
|
|
352 trailer = (struct stk_trailer *) trailer->link;
|
|
|
353 if ((block <= address) && (address < (block + size)))
|
|
|
354 break;
|
|
|
355 }
|
|
|
356
|
|
|
357 /* Set the result to the offset in this segment and add the sizes
|
|
|
358 of all predecessor segments. */
|
|
|
359
|
|
|
360 result = address - block;
|
|
|
361
|
|
|
362 if (trailer == 0)
|
|
|
363 {
|
|
|
364 return result;
|
|
|
365 }
|
|
|
366
|
|
|
367 do
|
|
|
368 {
|
|
|
369 if (trailer->this_size <= 0)
|
|
|
370 abort ();
|
|
|
371 result += trailer->this_size;
|
|
|
372 trailer = (struct stk_trailer *) trailer->link;
|
|
|
373 }
|
|
|
374 while (trailer != 0);
|
|
|
375
|
|
|
376 /* We are done. Note that if you present a bogus address (one
|
|
|
377 not in any segment), you will get a different number back, formed
|
|
|
378 from subtracting the address of the first block. This is probably
|
|
|
379 not what you want. */
|
|
|
380
|
|
|
381 return (result);
|
|
|
382 }
|
|
|
383
|
|
|
384 #else /* not CRAY2 */
|
|
|
385 /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP.
|
|
|
386 Determine the number of the cell within the stack,
|
|
|
387 given the address of the cell. The purpose of this
|
|
|
388 routine is to linearize, in some sense, stack addresses
|
|
|
389 for alloca. */
|
|
|
390
|
|
|
391 static long
|
|
|
392 i00afunc (long address)
|
|
|
393 {
|
|
|
394 long stkl = 0;
|
|
|
395
|
|
|
396 long size, pseg, this_segment, stack;
|
|
|
397 long result = 0;
|
|
|
398
|
|
|
399 struct stack_segment_linkage *ssptr;
|
|
|
400
|
|
|
401 /* Register B67 contains the address of the end of the
|
|
|
402 current stack segment. If you (as a subprogram) store
|
|
|
403 your registers on the stack and find that you are past
|
|
|
404 the contents of B67, you have overflowed the segment.
|
|
|
405
|
|
|
406 B67 also points to the stack segment linkage control
|
|
|
407 area, which is what we are really interested in. */
|
|
|
408
|
|
|
409 stkl = CRAY_STACKSEG_END ();
|
|
|
410 ssptr = (struct stack_segment_linkage *) stkl;
|
|
|
411
|
|
|
412 /* If one subtracts 'size' from the end of the segment,
|
|
|
413 one has the address of the first word of the segment.
|
|
|
414
|
|
|
415 If this is not the first segment, 'pseg' will be
|
|
|
416 nonzero. */
|
|
|
417
|
|
|
418 pseg = ssptr->sspseg;
|
|
|
419 size = ssptr->sssize;
|
|
|
420
|
|
|
421 this_segment = stkl - size;
|
|
|
422
|
|
|
423 /* It is possible that calling this routine itself caused
|
|
|
424 a stack overflow. Discard stack segments which do not
|
|
|
425 contain the target address. */
|
|
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426
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427 while (!(this_segment <= address && address <= stkl))
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428 {
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429 #ifdef DEBUG_I00AFUNC
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430 fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl);
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431 #endif
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432 if (pseg == 0)
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433 break;
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434 stkl = stkl - pseg;
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435 ssptr = (struct stack_segment_linkage *) stkl;
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436 size = ssptr->sssize;
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437 pseg = ssptr->sspseg;
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438 this_segment = stkl - size;
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439 }
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440
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441 result = address - this_segment;
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442
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443 /* If you subtract pseg from the current end of the stack,
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444 you get the address of the previous stack segment's end.
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445 This seems a little convoluted to me, but I'll bet you save
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446 a cycle somewhere. */
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447
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448 while (pseg != 0)
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449 {
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450 #ifdef DEBUG_I00AFUNC
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451 fprintf (stderr, "%011o %011o\n", pseg, size);
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452 #endif
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453 stkl = stkl - pseg;
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454 ssptr = (struct stack_segment_linkage *) stkl;
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455 size = ssptr->sssize;
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456 pseg = ssptr->sspseg;
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457 result += size;
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458 }
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459 return (result);
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460 }
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461
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462 #endif /* not CRAY2 */
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463 #endif /* CRAY */
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