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/* alloca.c -- allocate automatically reclaimed memory
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(Mostly) portable public-domain implementation -- D A Gwyn
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This implementation of the PWB library alloca function,
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which is used to allocate space off the run-time stack so
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that it is automatically reclaimed upon procedure exit,
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was inspired by discussions with J. Q. Johnson of Cornell.
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J.Otto Tennant <jot@cray.com> contributed the Cray support.
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a2ae7a |
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There are some preprocessor constants that can
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be defined when compiling for your specific system, for
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improved efficiency; however, the defaults should be okay.
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The general concept of this implementation is to keep
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track of all alloca-allocated blocks, and reclaim any
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that are found to be deeper in the stack than the current
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invocation. This heuristic does not reclaim storage as
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soon as it becomes invalid, but it will do so eventually.
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As a special case, alloca(0) reclaims storage without
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allocating any. It is a good idea to use alloca(0) in
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your main control loop, etc. to force garbage collection. */
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#include <config.h>
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a2ae7a |
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#include <alloca.h>
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#include <string.h>
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#include <stdlib.h>
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#ifdef emacs
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# include "lisp.h"
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# include "blockinput.h"
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# ifdef EMACS_FREE
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# undef free
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# define free EMACS_FREE
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# endif
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#else
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# define memory_full() abort ()
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#endif
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/* If compiling with GCC 2, this file's not needed. */
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#if !defined (__GNUC__) || __GNUC__ < 2
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/* If someone has defined alloca as a macro,
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there must be some other way alloca is supposed to work. */
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# ifndef alloca
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# ifdef emacs
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# ifdef static
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/* actually, only want this if static is defined as ""
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-- this is for usg, in which emacs must undefine static
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in order to make unexec workable
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*/
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# ifndef STACK_DIRECTION
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you
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lose
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-- must know STACK_DIRECTION at compile-time
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/* Using #error here is not wise since this file should work for
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old and obscure compilers. */
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# endif /* STACK_DIRECTION undefined */
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# endif /* static */
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# endif /* emacs */
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/* If your stack is a linked list of frames, you have to
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provide an "address metric" ADDRESS_FUNCTION macro. */
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# if defined (CRAY) && defined (CRAY_STACKSEG_END)
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long i00afunc ();
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# define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg))
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# else
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# define ADDRESS_FUNCTION(arg) &(arg)
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# endif
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/* Define STACK_DIRECTION if you know the direction of stack
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growth for your system; otherwise it will be automatically
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deduced at run-time.
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STACK_DIRECTION > 0 => grows toward higher addresses
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STACK_DIRECTION < 0 => grows toward lower addresses
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STACK_DIRECTION = 0 => direction of growth unknown */
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# ifndef STACK_DIRECTION
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# define STACK_DIRECTION 0 /* Direction unknown. */
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# endif
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# if STACK_DIRECTION != 0
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# define STACK_DIR STACK_DIRECTION /* Known at compile-time. */
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# else /* STACK_DIRECTION == 0; need run-time code. */
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static int stack_dir; /* 1 or -1 once known. */
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# define STACK_DIR stack_dir
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static int
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find_stack_direction (int *addr, int depth)
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{
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int dir, dummy = 0;
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if (! addr)
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addr = &dummy;
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*addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
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dir = depth ? find_stack_direction (addr, depth - 1) : 0;
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return dir + dummy;
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}
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# endif /* STACK_DIRECTION == 0 */
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/* An "alloca header" is used to:
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(a) chain together all alloca'ed blocks;
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(b) keep track of stack depth.
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It is very important that sizeof(header) agree with malloc
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alignment chunk size. The following default should work okay. */
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# ifndef ALIGN_SIZE
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# define ALIGN_SIZE sizeof(double)
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# endif
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typedef union hdr
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{
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char align[ALIGN_SIZE]; /* To force sizeof(header). */
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struct
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{
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union hdr *next; /* For chaining headers. */
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char *deep; /* For stack depth measure. */
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} h;
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} header;
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static header *last_alloca_header = NULL; /* -> last alloca header. */
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/* Return a pointer to at least SIZE bytes of storage,
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which will be automatically reclaimed upon exit from
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the procedure that called alloca. Originally, this space
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was supposed to be taken from the current stack frame of the
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caller, but that method cannot be made to work for some
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implementations of C, for example under Gould's UTX/32. */
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void *
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alloca (size_t size)
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{
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auto char probe; /* Probes stack depth: */
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register char *depth = ADDRESS_FUNCTION (probe);
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# if STACK_DIRECTION == 0
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if (STACK_DIR == 0) /* Unknown growth direction. */
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STACK_DIR = find_stack_direction (NULL, (size & 1) + 20);
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# endif
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/* Reclaim garbage, defined as all alloca'd storage that
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was allocated from deeper in the stack than currently. */
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{
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register header *hp; /* Traverses linked list. */
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# ifdef emacs
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BLOCK_INPUT;
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# endif
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for (hp = last_alloca_header; hp != NULL;)
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if ((STACK_DIR > 0 && hp->h.deep > depth)
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|| (STACK_DIR < 0 && hp->h.deep < depth))
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{
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register header *np = hp->h.next;
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free (hp); /* Collect garbage. */
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hp = np; /* -> next header. */
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}
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else
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break; /* Rest are not deeper. */
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last_alloca_header = hp; /* -> last valid storage. */
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# ifdef emacs
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UNBLOCK_INPUT;
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# endif
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}
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if (size == 0)
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return NULL; /* No allocation required. */
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/* Allocate combined header + user data storage. */
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{
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a2ae7a |
/* Address of header. */
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a2ae7a |
register header *new;
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a2ae7a |
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size_t combined_size = sizeof (header) + size;
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if (combined_size < sizeof (header))
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memory_full ();
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new = malloc (combined_size);
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if (! new)
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memory_full ();
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new->h.next = last_alloca_header;
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new->h.deep = depth;
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last_alloca_header = new;
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/* User storage begins just after header. */
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return (void *) (new + 1);
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}
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}
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# if defined (CRAY) && defined (CRAY_STACKSEG_END)
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a2ae7a |
|
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a2ae7a |
# ifdef DEBUG_I00AFUNC
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# include <stdio.h>
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# endif
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a2ae7a |
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# ifndef CRAY_STACK
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# define CRAY_STACK
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a2ae7a |
# ifndef CRAY2
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a2ae7a |
/* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */
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struct stack_control_header
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{
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a2ae7a |
long shgrow:32; /* Number of times stack has grown. */
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a2ae7a |
long shaseg:32; /* Size of increments to stack. */
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long shhwm:32; /* High water mark of stack. */
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long shsize:32; /* Current size of stack (all segments). */
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};
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a2ae7a |
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/* The stack segment linkage control information occurs at
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a2ae7a |
the high-address end of a stack segment. (The stack
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a2ae7a |
grows from low addresses to high addresses.) The initial
|
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a2ae7a |
part of the stack segment linkage control information is
|
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a2ae7a |
0200 (octal) words. This provides for register storage
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for the routine which overflows the stack. */
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a2ae7a |
|
|
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a2ae7a |
struct stack_segment_linkage
|
|
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a2ae7a |
{
|
|
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a2ae7a |
long ss[0200]; /* 0200 overflow words. */
|
|
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a2ae7a |
long sssize:32; /* Number of words in this segment. */
|
|
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a2ae7a |
long ssbase:32; /* Offset to stack base. */
|
|
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a2ae7a |
long:32;
|
|
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a2ae7a |
long sspseg:32; /* Offset to linkage control of previous
|
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a2ae7a |
segment of stack. */
|
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a2ae7a |
long:32;
|
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a2ae7a |
long sstcpt:32; /* Pointer to task common address block. */
|
|
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a2ae7a |
long sscsnm; /* Private control structure number for
|
|
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a2ae7a |
microtasking. */
|
|
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a2ae7a |
long ssusr1; /* Reserved for user. */
|
|
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a2ae7a |
long ssusr2; /* Reserved for user. */
|
|
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a2ae7a |
long sstpid; /* Process ID for pid based multi-tasking. */
|
|
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a2ae7a |
long ssgvup; /* Pointer to multitasking thread giveup. */
|
|
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a2ae7a |
long sscray[7]; /* Reserved for Cray Research. */
|
|
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a2ae7a |
long ssa0;
|
|
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a2ae7a |
long ssa1;
|
|
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a2ae7a |
long ssa2;
|
|
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a2ae7a |
long ssa3;
|
|
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a2ae7a |
long ssa4;
|
|
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a2ae7a |
long ssa5;
|
|
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a2ae7a |
long ssa6;
|
|
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a2ae7a |
long ssa7;
|
|
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a2ae7a |
long sss0;
|
|
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a2ae7a |
long sss1;
|
|
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a2ae7a |
long sss2;
|
|
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a2ae7a |
long sss3;
|
|
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a2ae7a |
long sss4;
|
|
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a2ae7a |
long sss5;
|
|
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a2ae7a |
long sss6;
|
|
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a2ae7a |
long sss7;
|
|
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a2ae7a |
};
|
|
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a2ae7a |
|
|
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a2ae7a |
# else /* CRAY2 */
|
|
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a2ae7a |
/* The following structure defines the vector of words
|
|
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a2ae7a |
returned by the STKSTAT library routine. */
|
|
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a2ae7a |
struct stk_stat
|
|
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a2ae7a |
{
|
|
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a2ae7a |
long now; /* Current total stack size. */
|
|
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a2ae7a |
long maxc; /* Amount of contiguous space which would
|
|
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a2ae7a |
be required to satisfy the maximum
|
|
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a2ae7a |
stack demand to date. */
|
|
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a2ae7a |
long high_water; /* Stack high-water mark. */
|
|
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a2ae7a |
long overflows; /* Number of stack overflow ($STKOFEN) calls. */
|
|
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a2ae7a |
long hits; /* Number of internal buffer hits. */
|
|
Packit Service |
a2ae7a |
long extends; /* Number of block extensions. */
|
|
Packit Service |
a2ae7a |
long stko_mallocs; /* Block allocations by $STKOFEN. */
|
|
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a2ae7a |
long underflows; /* Number of stack underflow calls ($STKRETN). */
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a2ae7a |
long stko_free; /* Number of deallocations by $STKRETN. */
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a2ae7a |
long stkm_free; /* Number of deallocations by $STKMRET. */
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a2ae7a |
long segments; /* Current number of stack segments. */
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a2ae7a |
long maxs; /* Maximum number of stack segments so far. */
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a2ae7a |
long pad_size; /* Stack pad size. */
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a2ae7a |
long current_address; /* Current stack segment address. */
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a2ae7a |
long current_size; /* Current stack segment size. This
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a2ae7a |
number is actually corrupted by STKSTAT to
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a2ae7a |
include the fifteen word trailer area. */
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a2ae7a |
long initial_address; /* Address of initial segment. */
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a2ae7a |
long initial_size; /* Size of initial segment. */
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a2ae7a |
};
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a2ae7a |
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a2ae7a |
/* The following structure describes the data structure which trails
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a2ae7a |
any stack segment. I think that the description in 'asdef' is
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a2ae7a |
out of date. I only describe the parts that I am sure about. */
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a2ae7a |
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a2ae7a |
struct stk_trailer
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a2ae7a |
{
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a2ae7a |
long this_address; /* Address of this block. */
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a2ae7a |
long this_size; /* Size of this block (does not include
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a2ae7a |
this trailer). */
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a2ae7a |
long unknown2;
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a2ae7a |
long unknown3;
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a2ae7a |
long link; /* Address of trailer block of previous
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a2ae7a |
segment. */
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a2ae7a |
long unknown5;
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a2ae7a |
long unknown6;
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a2ae7a |
long unknown7;
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a2ae7a |
long unknown8;
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a2ae7a |
long unknown9;
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a2ae7a |
long unknown10;
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a2ae7a |
long unknown11;
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a2ae7a |
long unknown12;
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a2ae7a |
long unknown13;
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a2ae7a |
long unknown14;
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a2ae7a |
};
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a2ae7a |
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a2ae7a |
# endif /* CRAY2 */
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a2ae7a |
# endif /* not CRAY_STACK */
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a2ae7a |
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a2ae7a |
# ifdef CRAY2
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a2ae7a |
/* Determine a "stack measure" for an arbitrary ADDRESS.
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a2ae7a |
I doubt that "lint" will like this much. */
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a2ae7a |
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a2ae7a |
static long
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a2ae7a |
i00afunc (long *address)
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a2ae7a |
{
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a2ae7a |
struct stk_stat status;
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a2ae7a |
struct stk_trailer *trailer;
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a2ae7a |
long *block, size;
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a2ae7a |
long result = 0;
|
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a2ae7a |
|
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a2ae7a |
/* We want to iterate through all of the segments. The first
|
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a2ae7a |
step is to get the stack status structure. We could do this
|
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a2ae7a |
more quickly and more directly, perhaps, by referencing the
|
|
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a2ae7a |
$LM00 common block, but I know that this works. */
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a2ae7a |
|
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a2ae7a |
STKSTAT (&status);
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a2ae7a |
|
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a2ae7a |
/* Set up the iteration. */
|
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a2ae7a |
|
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a2ae7a |
trailer = (struct stk_trailer *) (status.current_address
|
|
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a2ae7a |
+ status.current_size
|
|
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a2ae7a |
- 15);
|
|
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a2ae7a |
|
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a2ae7a |
/* There must be at least one stack segment. Therefore it is
|
|
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a2ae7a |
a fatal error if "trailer" is null. */
|
|
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a2ae7a |
|
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a2ae7a |
if (trailer == NULL)
|
|
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a2ae7a |
abort ();
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* Discard segments that do not contain our argument address. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
while (trailer != NULL)
|
|
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a2ae7a |
{
|
|
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a2ae7a |
block = (long *) trailer->this_address;
|
|
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a2ae7a |
size = trailer->this_size;
|
|
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a2ae7a |
if (block == NULL || size == 0)
|
|
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a2ae7a |
abort ();
|
|
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a2ae7a |
trailer = (struct stk_trailer *) trailer->link;
|
|
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a2ae7a |
if ((block <= address) && (address < (block + size)))
|
|
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a2ae7a |
break;
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* Set the result to the offset in this segment and add the sizes
|
|
Packit Service |
a2ae7a |
of all predecessor segments. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
result = address - block;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
if (trailer == NULL)
|
|
Packit Service |
a2ae7a |
{
|
|
Packit Service |
a2ae7a |
return result;
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
do
|
|
Packit Service |
a2ae7a |
{
|
|
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a2ae7a |
if (trailer->this_size <= 0)
|
|
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a2ae7a |
abort ();
|
|
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a2ae7a |
result += trailer->this_size;
|
|
Packit Service |
a2ae7a |
trailer = (struct stk_trailer *) trailer->link;
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
while (trailer != NULL);
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* We are done. Note that if you present a bogus address (one
|
|
Packit Service |
a2ae7a |
not in any segment), you will get a different number back, formed
|
|
Packit Service |
a2ae7a |
from subtracting the address of the first block. This is probably
|
|
Packit Service |
a2ae7a |
not what you want. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
return (result);
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
# else /* not CRAY2 */
|
|
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a2ae7a |
/* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP.
|
|
Packit Service |
a2ae7a |
Determine the number of the cell within the stack,
|
|
Packit Service |
a2ae7a |
given the address of the cell. The purpose of this
|
|
Packit Service |
a2ae7a |
routine is to linearize, in some sense, stack addresses
|
|
Packit Service |
a2ae7a |
for alloca. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
static long
|
|
Packit Service |
a2ae7a |
i00afunc (long address)
|
|
Packit Service |
a2ae7a |
{
|
|
Packit Service |
a2ae7a |
long stkl = 0;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
long size, pseg, this_segment, stack;
|
|
Packit Service |
a2ae7a |
long result = 0;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
struct stack_segment_linkage *ssptr;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* Register B67 contains the address of the end of the
|
|
Packit Service |
a2ae7a |
current stack segment. If you (as a subprogram) store
|
|
Packit Service |
a2ae7a |
your registers on the stack and find that you are past
|
|
Packit Service |
a2ae7a |
the contents of B67, you have overflowed the segment.
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
B67 also points to the stack segment linkage control
|
|
Packit Service |
a2ae7a |
area, which is what we are really interested in. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
stkl = CRAY_STACKSEG_END ();
|
|
Packit Service |
a2ae7a |
ssptr = (struct stack_segment_linkage *) stkl;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* If one subtracts 'size' from the end of the segment,
|
|
Packit Service |
a2ae7a |
one has the address of the first word of the segment.
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
If this is not the first segment, 'pseg' will be
|
|
Packit Service |
a2ae7a |
nonzero. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
pseg = ssptr->sspseg;
|
|
Packit Service |
a2ae7a |
size = ssptr->sssize;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
this_segment = stkl - size;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* It is possible that calling this routine itself caused
|
|
Packit Service |
a2ae7a |
a stack overflow. Discard stack segments which do not
|
|
Packit Service |
a2ae7a |
contain the target address. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
while (!(this_segment <= address && address <= stkl))
|
|
Packit Service |
a2ae7a |
{
|
|
Packit Service |
a2ae7a |
# ifdef DEBUG_I00AFUNC
|
|
Packit Service |
a2ae7a |
fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl);
|
|
Packit Service |
a2ae7a |
# endif
|
|
Packit Service |
a2ae7a |
if (pseg == 0)
|
|
Packit Service |
a2ae7a |
break;
|
|
Packit Service |
a2ae7a |
stkl = stkl - pseg;
|
|
Packit Service |
a2ae7a |
ssptr = (struct stack_segment_linkage *) stkl;
|
|
Packit Service |
a2ae7a |
size = ssptr->sssize;
|
|
Packit Service |
a2ae7a |
pseg = ssptr->sspseg;
|
|
Packit Service |
a2ae7a |
this_segment = stkl - size;
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
result = address - this_segment;
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
/* If you subtract pseg from the current end of the stack,
|
|
Packit Service |
a2ae7a |
you get the address of the previous stack segment's end.
|
|
Packit Service |
a2ae7a |
This seems a little convoluted to me, but I'll bet you save
|
|
Packit Service |
a2ae7a |
a cycle somewhere. */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
while (pseg != 0)
|
|
Packit Service |
a2ae7a |
{
|
|
Packit Service |
a2ae7a |
# ifdef DEBUG_I00AFUNC
|
|
Packit Service |
a2ae7a |
fprintf (stderr, "%011o %011o\n", pseg, size);
|
|
Packit Service |
a2ae7a |
# endif
|
|
Packit Service |
a2ae7a |
stkl = stkl - pseg;
|
|
Packit Service |
a2ae7a |
ssptr = (struct stack_segment_linkage *) stkl;
|
|
Packit Service |
a2ae7a |
size = ssptr->sssize;
|
|
Packit Service |
a2ae7a |
pseg = ssptr->sspseg;
|
|
Packit Service |
a2ae7a |
result += size;
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
return (result);
|
|
Packit Service |
a2ae7a |
}
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
# endif /* not CRAY2 */
|
|
Packit Service |
a2ae7a |
# endif /* CRAY */
|
|
Packit Service |
a2ae7a |
|
|
Packit Service |
a2ae7a |
# endif /* no alloca */
|
|
Packit Service |
a2ae7a |
#endif /* not GCC 2 */
|