| 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 | /* | 
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| 25 |  | 
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| 26 | @deftypefn Replacement void* alloca (size_t @var{size}) | 
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| 27 |  | 
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| 28 | This function allocates memory which will be automatically reclaimed | 
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| 29 | after the procedure exits.  The @libib{} implementation does not free | 
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| 30 | the memory immediately but will do so eventually during subsequent | 
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| 31 | calls to this function.  Memory is allocated using @code{xmalloc} under | 
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| 32 | normal circumstances. | 
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| 33 |  | 
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| 34 | The header file @file{alloca-conf.h} can be used in conjunction with the | 
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| 35 | GNU Autoconf test @code{AC_FUNC_ALLOCA} to test for and properly make | 
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| 36 | available this function.  The @code{AC_FUNC_ALLOCA} test requires that | 
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| 37 | client code use a block of preprocessor code to be safe (see the Autoconf | 
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| 38 | manual for more); this header incorporates that logic and more, including | 
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| 39 | the possibility of a GCC built-in function. | 
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| 40 |  | 
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| 41 | @end deftypefn | 
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| 42 |  | 
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| 43 | */ | 
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| 44 |  | 
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| 45 | #ifdef HAVE_CONFIG_H | 
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| 46 | #include <config.h> | 
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| 47 | #endif | 
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| 48 |  | 
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| 49 | #include <libiberty.h> | 
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| 50 |  | 
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| 51 | #ifdef HAVE_STRING_H | 
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| 52 | #include <string.h> | 
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| 53 | #endif | 
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| 54 | #ifdef HAVE_STDLIB_H | 
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| 55 | #include <stdlib.h> | 
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| 56 | #endif | 
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| 57 |  | 
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| 58 | /* These variables are used by the ASTRDUP implementation that relies | 
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| 59 | on C_alloca.  */ | 
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| 60 | const char *libiberty_optr; | 
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| 61 | char *libiberty_nptr; | 
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| 62 | unsigned long libiberty_len; | 
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| 63 |  | 
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| 64 | /* If your stack is a linked list of frames, you have to | 
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| 65 | provide an "address metric" ADDRESS_FUNCTION macro.  */ | 
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| 66 |  | 
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| 67 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | 
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| 68 | static long i00afunc (); | 
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| 69 | #define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg)) | 
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| 70 | #else | 
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| 71 | #define ADDRESS_FUNCTION(arg) &(arg) | 
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| 72 | #endif | 
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| 73 |  | 
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| 74 | #ifndef NULL | 
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| 75 | #define NULL    0 | 
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| 76 | #endif | 
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| 77 |  | 
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| 78 | /* Define STACK_DIRECTION if you know the direction of stack | 
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| 79 | growth for your system; otherwise it will be automatically | 
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| 80 | deduced at run-time. | 
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| 81 |  | 
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| 82 | STACK_DIRECTION > 0 => grows toward higher addresses | 
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| 83 | STACK_DIRECTION < 0 => grows toward lower addresses | 
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| 84 | STACK_DIRECTION = 0 => direction of growth unknown  */ | 
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| 85 |  | 
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| 86 | #ifndef STACK_DIRECTION | 
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| 87 | #define STACK_DIRECTION 0       /* Direction unknown.  */ | 
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| 88 | #endif | 
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| 89 |  | 
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| 90 | #if STACK_DIRECTION != 0 | 
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| 91 |  | 
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| 92 | #define STACK_DIR       STACK_DIRECTION /* Known at compile-time.  */ | 
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| 93 |  | 
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| 94 | #else /* STACK_DIRECTION == 0; need run-time code.  */ | 
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| 95 |  | 
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| 96 | static int stack_dir;           /* 1 or -1 once known.  */ | 
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| 97 | #define STACK_DIR       stack_dir | 
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| 98 |  | 
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| 99 | static void | 
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| 100 | find_stack_direction () | 
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| 101 | { | 
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| 102 | static char *addr = NULL;     /* Address of first `dummy', once known.  */ | 
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| 103 | auto char dummy;              /* To get stack address.  */ | 
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| 104 |  | 
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| 105 | if (addr == NULL) | 
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| 106 | {                           /* Initial entry.  */ | 
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| 107 | addr = ADDRESS_FUNCTION (dummy); | 
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| 108 |  | 
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| 109 | find_stack_direction ();  /* Recurse once.  */ | 
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| 110 | } | 
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| 111 | else | 
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| 112 | { | 
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| 113 | /* Second entry.  */ | 
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| 114 | if (ADDRESS_FUNCTION (dummy) > addr) | 
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| 115 | stack_dir = 1;          /* Stack grew upward.  */ | 
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| 116 | else | 
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| 117 | stack_dir = -1;         /* Stack grew downward.  */ | 
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| 118 | } | 
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| 119 | } | 
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| 120 |  | 
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| 121 | #endif /* STACK_DIRECTION == 0 */ | 
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| 122 |  | 
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| 123 | /* An "alloca header" is used to: | 
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| 124 | (a) chain together all alloca'ed blocks; | 
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| 125 | (b) keep track of stack depth. | 
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| 126 |  | 
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| 127 | It is very important that sizeof(header) agree with malloc | 
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| 128 | alignment chunk size.  The following default should work okay.  */ | 
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| 129 |  | 
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| 130 | #ifndef ALIGN_SIZE | 
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| 131 | #define ALIGN_SIZE      sizeof(double) | 
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| 132 | #endif | 
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| 133 |  | 
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| 134 | typedef union hdr | 
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| 135 | { | 
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| 136 | char align[ALIGN_SIZE];       /* To force sizeof(header).  */ | 
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| 137 | struct | 
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| 138 | { | 
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| 139 | union hdr *next;          /* For chaining headers.  */ | 
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| 140 | char *deep;               /* For stack depth measure.  */ | 
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| 141 | } h; | 
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| 142 | } header; | 
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| 143 |  | 
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| 144 | static header *last_alloca_header = NULL;       /* -> last alloca header.  */ | 
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| 145 |  | 
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| 146 | /* Return a pointer to at least SIZE bytes of storage, | 
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| 147 | which will be automatically reclaimed upon exit from | 
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| 148 | the procedure that called alloca.  Originally, this space | 
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| 149 | was supposed to be taken from the current stack frame of the | 
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| 150 | caller, but that method cannot be made to work for some | 
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| 151 | implementations of C, for example under Gould's UTX/32.  */ | 
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| 152 |  | 
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| 153 | /* @undocumented C_alloca */ | 
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| 154 |  | 
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| 155 | PTR | 
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| 156 | C_alloca (size) | 
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| 157 | size_t size; | 
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| 158 | { | 
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| 159 | auto char probe;              /* Probes stack depth: */ | 
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| 160 | register char *depth = ADDRESS_FUNCTION (probe); | 
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| 161 |  | 
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| 162 | #if STACK_DIRECTION == 0 | 
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| 163 | if (STACK_DIR == 0)           /* Unknown growth direction.  */ | 
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| 164 | find_stack_direction (); | 
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| 165 | #endif | 
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| 166 |  | 
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| 167 | /* Reclaim garbage, defined as all alloca'd storage that | 
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| 168 | was allocated from deeper in the stack than currently.  */ | 
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| 169 |  | 
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| 170 | { | 
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| 171 | register header *hp;        /* Traverses linked list.  */ | 
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| 172 |  | 
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| 173 | for (hp = last_alloca_header; hp != NULL;) | 
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| 174 | if ((STACK_DIR > 0 && hp->h.deep > depth) | 
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| 175 | || (STACK_DIR < 0 && hp->h.deep < depth)) | 
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| 176 | { | 
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| 177 | register header *np = hp->h.next; | 
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| 178 |  | 
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| 179 | free ((PTR) hp);      /* Collect garbage.  */ | 
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| 180 |  | 
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| 181 | hp = np;              /* -> next header.  */ | 
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| 182 | } | 
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| 183 | else | 
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| 184 | break;                  /* Rest are not deeper.  */ | 
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| 185 |  | 
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| 186 | last_alloca_header = hp;    /* -> last valid storage.  */ | 
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| 187 | } | 
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| 188 |  | 
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| 189 | if (size == 0) | 
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| 190 | return NULL;                /* No allocation required.  */ | 
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| 191 |  | 
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| 192 | /* Allocate combined header + user data storage.  */ | 
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| 193 |  | 
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| 194 | { | 
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| 195 | register PTR new = xmalloc (sizeof (header) + size); | 
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| 196 | /* Address of header.  */ | 
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| 197 |  | 
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| 198 | if (new == 0) | 
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| 199 | abort(); | 
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| 200 |  | 
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| 201 | ((header *) new)->h.next = last_alloca_header; | 
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| 202 | ((header *) new)->h.deep = depth; | 
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| 203 |  | 
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| 204 | last_alloca_header = (header *) new; | 
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| 205 |  | 
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| 206 | /* User storage begins just after header.  */ | 
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| 207 |  | 
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| 208 | return (PTR) ((char *) new + sizeof (header)); | 
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| 209 | } | 
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| 210 | } | 
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| 211 |  | 
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| 212 | #if defined (CRAY) && defined (CRAY_STACKSEG_END) | 
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| 213 |  | 
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| 214 | #ifdef DEBUG_I00AFUNC | 
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| 215 | #include <stdio.h> | 
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| 216 | #endif | 
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| 217 |  | 
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| 218 | #ifndef CRAY_STACK | 
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| 219 | #define CRAY_STACK | 
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| 220 | #ifndef CRAY2 | 
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| 221 | /* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */ | 
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| 222 | struct stack_control_header | 
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| 223 | { | 
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| 224 | long shgrow:32;             /* Number of times stack has grown.  */ | 
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| 225 | long shaseg:32;             /* Size of increments to stack.  */ | 
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| 226 | long shhwm:32;              /* High water mark of stack.  */ | 
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| 227 | long shsize:32;             /* Current size of stack (all segments).  */ | 
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| 228 | }; | 
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| 229 |  | 
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| 230 | /* The stack segment linkage control information occurs at | 
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| 231 | the high-address end of a stack segment.  (The stack | 
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| 232 | grows from low addresses to high addresses.)  The initial | 
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| 233 | part of the stack segment linkage control information is | 
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| 234 | 0200 (octal) words.  This provides for register storage | 
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| 235 | for the routine which overflows the stack.  */ | 
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| 236 |  | 
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| 237 | struct stack_segment_linkage | 
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| 238 | { | 
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| 239 | long ss[0200];              /* 0200 overflow words.  */ | 
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| 240 | long sssize:32;             /* Number of words in this segment.  */ | 
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| 241 | long ssbase:32;             /* Offset to stack base.  */ | 
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| 242 | long:32; | 
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| 243 | long sspseg:32;             /* Offset to linkage control of previous | 
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| 244 | segment of stack.  */ | 
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| 245 | long:32; | 
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| 246 | long sstcpt:32;             /* Pointer to task common address block.  */ | 
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| 247 | long sscsnm;                /* Private control structure number for | 
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| 248 | microtasking.  */ | 
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| 249 | long ssusr1;                /* Reserved for user.  */ | 
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| 250 | long ssusr2;                /* Reserved for user.  */ | 
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| 251 | long sstpid;                /* Process ID for pid based multi-tasking.  */ | 
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| 252 | long ssgvup;                /* Pointer to multitasking thread giveup.  */ | 
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| 253 | long sscray[7];             /* Reserved for Cray Research.  */ | 
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| 254 | long ssa0; | 
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| 255 | long ssa1; | 
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| 256 | long ssa2; | 
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| 257 | long ssa3; | 
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| 258 | long ssa4; | 
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| 259 | long ssa5; | 
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| 260 | long ssa6; | 
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| 261 | long ssa7; | 
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| 262 | long sss0; | 
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| 263 | long sss1; | 
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| 264 | long sss2; | 
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| 265 | long sss3; | 
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| 266 | long sss4; | 
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| 267 | long sss5; | 
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| 268 | long sss6; | 
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| 269 | long sss7; | 
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| 270 | }; | 
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| 271 |  | 
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| 272 | #else /* CRAY2 */ | 
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| 273 | /* The following structure defines the vector of words | 
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| 274 | returned by the STKSTAT library routine.  */ | 
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| 275 | struct stk_stat | 
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| 276 | { | 
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| 277 | long now;                   /* Current total stack size.  */ | 
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| 278 | long maxc;                  /* Amount of contiguous space which would | 
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| 279 | be required to satisfy the maximum | 
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| 280 | stack demand to date.  */ | 
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| 281 | long high_water;            /* Stack high-water mark.  */ | 
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| 282 | long overflows;             /* Number of stack overflow ($STKOFEN) calls.  */ | 
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| 283 | long hits;                  /* Number of internal buffer hits.  */ | 
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| 284 | long extends;               /* Number of block extensions.  */ | 
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| 285 | long stko_mallocs;          /* Block allocations by $STKOFEN.  */ | 
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| 286 | long underflows;            /* Number of stack underflow calls ($STKRETN).  */ | 
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| 287 | long stko_free;             /* Number of deallocations by $STKRETN.  */ | 
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| 288 | long stkm_free;             /* Number of deallocations by $STKMRET.  */ | 
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| 289 | long segments;              /* Current number of stack segments.  */ | 
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| 290 | long maxs;                  /* Maximum number of stack segments so far.  */ | 
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| 291 | long pad_size;              /* Stack pad size.  */ | 
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| 292 | long current_address;       /* Current stack segment address.  */ | 
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| 293 | long current_size;          /* Current stack segment size.  This | 
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| 294 | number is actually corrupted by STKSTAT to | 
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| 295 | include the fifteen word trailer area.  */ | 
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| 296 | long initial_address;       /* Address of initial segment.  */ | 
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| 297 | long initial_size;          /* Size of initial segment.  */ | 
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| 298 | }; | 
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| 299 |  | 
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| 300 | /* The following structure describes the data structure which trails | 
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| 301 | any stack segment.  I think that the description in 'asdef' is | 
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| 302 | out of date.  I only describe the parts that I am sure about.  */ | 
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| 303 |  | 
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| 304 | struct stk_trailer | 
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| 305 | { | 
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| 306 | long this_address;          /* Address of this block.  */ | 
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| 307 | long this_size;             /* Size of this block (does not include | 
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| 308 | this trailer).  */ | 
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| 309 | long unknown2; | 
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| 310 | long unknown3; | 
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| 311 | long link;                  /* Address of trailer block of previous | 
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| 312 | segment.  */ | 
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| 313 | long unknown5; | 
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| 314 | long unknown6; | 
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| 315 | long unknown7; | 
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| 316 | long unknown8; | 
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| 317 | long unknown9; | 
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| 318 | long unknown10; | 
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| 319 | long unknown11; | 
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| 320 | long unknown12; | 
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| 321 | long unknown13; | 
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| 322 | long unknown14; | 
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| 323 | }; | 
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| 324 |  | 
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| 325 | #endif /* CRAY2 */ | 
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| 326 | #endif /* not CRAY_STACK */ | 
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| 327 |  | 
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| 328 | #ifdef CRAY2 | 
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| 329 | /* Determine a "stack measure" for an arbitrary ADDRESS. | 
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| 330 | I doubt that "lint" will like this much.  */ | 
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| 331 |  | 
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| 332 | static long | 
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| 333 | i00afunc (long *address) | 
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| 334 | { | 
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| 335 | struct stk_stat status; | 
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| 336 | struct stk_trailer *trailer; | 
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| 337 | long *block, size; | 
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| 338 | long result = 0; | 
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| 339 |  | 
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| 340 | /* We want to iterate through all of the segments.  The first | 
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| 341 | step is to get the stack status structure.  We could do this | 
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| 342 | more quickly and more directly, perhaps, by referencing the | 
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| 343 | $LM00 common block, but I know that this works.  */ | 
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| 344 |  | 
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| 345 | STKSTAT (&status); | 
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| 346 |  | 
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| 347 | /* Set up the iteration.  */ | 
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| 348 |  | 
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| 349 | trailer = (struct stk_trailer *) (status.current_address | 
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| 350 | + status.current_size | 
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| 351 | - 15); | 
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| 352 |  | 
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| 353 | /* There must be at least one stack segment.  Therefore it is | 
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| 354 | a fatal error if "trailer" is null.  */ | 
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| 355 |  | 
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| 356 | if (trailer == 0) | 
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| 357 | abort (); | 
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| 358 |  | 
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| 359 | /* Discard segments that do not contain our argument address.  */ | 
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| 360 |  | 
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| 361 | while (trailer != 0) | 
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| 362 | { | 
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| 363 | block = (long *) trailer->this_address; | 
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| 364 | size = trailer->this_size; | 
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| 365 | if (block == 0 || size == 0) | 
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| 366 | abort (); | 
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| 367 | trailer = (struct stk_trailer *) trailer->link; | 
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| 368 | if ((block <= address) && (address < (block + size))) | 
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| 369 | break; | 
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| 370 | } | 
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| 371 |  | 
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| 372 | /* Set the result to the offset in this segment and add the sizes | 
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| 373 | of all predecessor segments.  */ | 
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| 374 |  | 
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| 375 | result = address - block; | 
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| 376 |  | 
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| 377 | if (trailer == 0) | 
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| 378 | { | 
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| 379 | return result; | 
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| 380 | } | 
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| 381 |  | 
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| 382 | do | 
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| 383 | { | 
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| 384 | if (trailer->this_size <= 0) | 
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| 385 | abort (); | 
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| 386 | result += trailer->this_size; | 
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| 387 | trailer = (struct stk_trailer *) trailer->link; | 
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| 388 | } | 
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| 389 | while (trailer != 0); | 
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| 390 |  | 
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| 391 | /* We are done.  Note that if you present a bogus address (one | 
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| 392 | not in any segment), you will get a different number back, formed | 
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| 393 | from subtracting the address of the first block.  This is probably | 
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| 394 | not what you want.  */ | 
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| 395 |  | 
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| 396 | return (result); | 
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| 397 | } | 
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| 398 |  | 
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| 399 | #else /* not CRAY2 */ | 
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| 400 | /* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP. | 
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| 401 | Determine the number of the cell within the stack, | 
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| 402 | given the address of the cell.  The purpose of this | 
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| 403 | routine is to linearize, in some sense, stack addresses | 
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| 404 | for alloca.  */ | 
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| 405 |  | 
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| 406 | static long | 
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| 407 | i00afunc (long address) | 
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| 408 | { | 
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| 409 | long stkl = 0; | 
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| 410 |  | 
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| 411 | long size, pseg, this_segment, stack; | 
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| 412 | long result = 0; | 
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| 413 |  | 
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| 414 | struct stack_segment_linkage *ssptr; | 
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| 415 |  | 
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| 416 | /* Register B67 contains the address of the end of the | 
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| 417 | current stack segment.  If you (as a subprogram) store | 
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| 418 | your registers on the stack and find that you are past | 
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| 419 | the contents of B67, you have overflowed the segment. | 
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| 420 |  | 
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| 421 | B67 also points to the stack segment linkage control | 
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| 422 | area, which is what we are really interested in.  */ | 
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| 423 |  | 
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| 424 | stkl = CRAY_STACKSEG_END (); | 
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| 425 | ssptr = (struct stack_segment_linkage *) stkl; | 
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| 426 |  | 
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| 427 | /* If one subtracts 'size' from the end of the segment, | 
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| 428 | one has the address of the first word of the segment. | 
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| 429 |  | 
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| 430 | If this is not the first segment, 'pseg' will be | 
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| 431 | nonzero.  */ | 
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| 432 |  | 
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| 433 | pseg = ssptr->sspseg; | 
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| 434 | size = ssptr->sssize; | 
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| 435 |  | 
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| 436 | this_segment = stkl - size; | 
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| 437 |  | 
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| 438 | /* It is possible that calling this routine itself caused | 
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| 439 | a stack overflow.  Discard stack segments which do not | 
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| 440 | contain the target address.  */ | 
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| 441 |  | 
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| 442 | while (!(this_segment <= address && address <= stkl)) | 
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| 443 | { | 
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| 444 | #ifdef DEBUG_I00AFUNC | 
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| 445 | fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl); | 
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| 446 | #endif | 
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| 447 | if (pseg == 0) | 
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| 448 | break; | 
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| 449 | stkl = stkl - pseg; | 
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| 450 | ssptr = (struct stack_segment_linkage *) stkl; | 
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| 451 | size = ssptr->sssize; | 
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| 452 | pseg = ssptr->sspseg; | 
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| 453 | this_segment = stkl - size; | 
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| 454 | } | 
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| 455 |  | 
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| 456 | result = address - this_segment; | 
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| 457 |  | 
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| 458 | /* If you subtract pseg from the current end of the stack, | 
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| 459 | you get the address of the previous stack segment's end. | 
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| 460 | This seems a little convoluted to me, but I'll bet you save | 
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| 461 | a cycle somewhere.  */ | 
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| 462 |  | 
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| 463 | while (pseg != 0) | 
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| 464 | { | 
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| 465 | #ifdef DEBUG_I00AFUNC | 
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| 466 | fprintf (stderr, "%011o %011o\n", pseg, size); | 
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| 467 | #endif | 
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| 468 | stkl = stkl - pseg; | 
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| 469 | ssptr = (struct stack_segment_linkage *) stkl; | 
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| 470 | size = ssptr->sssize; | 
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| 471 | pseg = ssptr->sspseg; | 
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| 472 | result += size; | 
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| 473 | } | 
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| 474 | return (result); | 
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| 475 | } | 
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| 476 |  | 
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| 477 | #endif /* not CRAY2 */ | 
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| 478 | #endif /* CRAY */ | 
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