Changes to alloca.c [branch-1_4]

[Eric Blake]

CVSROOT:        /sources/m4
Module name:    m4
Branch:         branch-1_4
Changes by:     Eric Blake <ericb>      06/06/15 13:13:26

Index: alloca.c
===================================================================
RCS file: alloca.c
diff -N alloca.c
--- alloca.c    17 Feb 2000 03:03:19 -0000      1.1.1.1
+++ /dev/null   1 Jan 1970 00:00:00 -0000
@@ -1,492 +0,0 @@
-/* alloca.c -- allocate automatically reclaimed memory
-   (Mostly) portable public-domain implementation -- D A Gwyn
-
-   This implementation of the PWB library alloca function,
-   which is used to allocate space off the run-time stack so
-   that it is automatically reclaimed upon procedure exit,
-   was inspired by discussions with J. Q. Johnson of Cornell.
-   J.Otto Tennant <address@hidden> contributed the Cray support.
-
-   There are some preprocessor constants that can
-   be defined when compiling for your specific system, for
-   improved efficiency; however, the defaults should be okay.
-
-   The general concept of this implementation is to keep
-   track of all alloca-allocated blocks, and reclaim any
-   that are found to be deeper in the stack than the current
-   invocation.  This heuristic does not reclaim storage as
-   soon as it becomes invalid, but it will do so eventually.
-
-   As a special case, alloca(0) reclaims storage without
-   allocating any.  It is a good idea to use alloca(0) in
-   your main control loop, etc. to force garbage collection.  */
-
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-#ifdef emacs
-#include "blockinput.h"
-#endif
-
-/* If compiling with GCC 2, this file's not needed.  */
-#if !defined (__GNUC__) || __GNUC__ < 2
-
-/* If someone has defined alloca as a macro,
-   there must be some other way alloca is supposed to work.  */
-#ifndef alloca
-
-#ifdef emacs
-#ifdef static
-/* actually, only want this if static is defined as ""
-   -- this is for usg, in which emacs must undefine static
-   in order to make unexec workable
-   */
-#ifndef STACK_DIRECTION
-you
-lose
--- must know STACK_DIRECTION at compile-time
-#endif /* STACK_DIRECTION undefined */
-#endif /* static */
-#endif /* emacs */
-
-/* If your stack is a linked list of frames, you have to
-   provide an "address metric" ADDRESS_FUNCTION macro.  */
-
-#if defined (CRAY) && defined (CRAY_STACKSEG_END)
-long i00afunc ();
-#define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg))
-#else
-#define ADDRESS_FUNCTION(arg) &(arg)
-#endif
-
-#if __STDC__
-typedef void *pointer;
-#else
-typedef char *pointer;
-#endif
-
-#define        NULL    0
-
-/* Different portions of Emacs need to call different versions of
-   malloc.  The Emacs executable needs alloca to call xmalloc, because
-   ordinary malloc isn't protected from input signals.  On the other
-   hand, the utilities in lib-src need alloca to call malloc; some of
-   them are very simple, and don't have an xmalloc routine.
-
-   Non-Emacs programs expect this to call use xmalloc.
-
-   Callers below should use malloc.  */
-
-#ifndef emacs
-#define malloc xmalloc
-#endif
-extern pointer malloc ();
-
-/* Define STACK_DIRECTION if you know the direction of stack
-   growth for your system; otherwise it will be automatically
-   deduced at run-time.
-
-   STACK_DIRECTION > 0 => grows toward higher addresses
-   STACK_DIRECTION < 0 => grows toward lower addresses
-   STACK_DIRECTION = 0 => direction of growth unknown  */
-
-#ifndef STACK_DIRECTION
-#define        STACK_DIRECTION 0       /* Direction unknown.  */
-#endif
-
-#if STACK_DIRECTION != 0
-
-#define        STACK_DIR       STACK_DIRECTION /* Known at compile-time.  */
-
-#else /* STACK_DIRECTION == 0; need run-time code.  */
-
-static int stack_dir;          /* 1 or -1 once known.  */
-#define        STACK_DIR       stack_dir
-
-static void
-find_stack_direction ()
-{
-  static char *addr = NULL;    /* Address of first `dummy', once known.  */
-  auto char dummy;             /* To get stack address.  */
-
-  if (addr == NULL)
-    {                          /* Initial entry.  */
-      addr = ADDRESS_FUNCTION (dummy);
-
-      find_stack_direction (); /* Recurse once.  */
-    }
-  else
-    {
-      /* Second entry.  */
-      if (ADDRESS_FUNCTION (dummy) > addr)
-       stack_dir = 1;          /* Stack grew upward.  */
-      else
-       stack_dir = -1;         /* Stack grew downward.  */
-    }
-}
-
-#endif /* STACK_DIRECTION == 0 */
-
-/* An "alloca header" is used to:
-   (a) chain together all alloca'ed blocks;
-   (b) keep track of stack depth.
-
-   It is very important that sizeof(header) agree with malloc
-   alignment chunk size.  The following default should work okay.  */
-
-#ifndef        ALIGN_SIZE
-#define        ALIGN_SIZE      sizeof(double)
-#endif
-
-typedef union hdr
-{
-  char align[ALIGN_SIZE];      /* To force sizeof(header).  */
-  struct
-    {
-      union hdr *next;         /* For chaining headers.  */
-      char *deep;              /* For stack depth measure.  */
-    } h;
-} header;
-
-static header *last_alloca_header = NULL;      /* -> last alloca header.  */
-
-/* Return a pointer to at least SIZE bytes of storage,
-   which will be automatically reclaimed upon exit from
-   the procedure that called alloca.  Originally, this space
-   was supposed to be taken from the current stack frame of the
-   caller, but that method cannot be made to work for some
-   implementations of C, for example under Gould's UTX/32.  */
-
-pointer
-alloca (size)
-     unsigned size;
-{
-  auto char probe;             /* Probes stack depth: */
-  register char *depth = ADDRESS_FUNCTION (probe);
-
-#if STACK_DIRECTION == 0
-  if (STACK_DIR == 0)          /* Unknown growth direction.  */
-    find_stack_direction ();
-#endif
-
-  /* Reclaim garbage, defined as all alloca'd storage that
-     was allocated from deeper in the stack than currently. */
-
-  {
-    register header *hp;       /* Traverses linked list.  */
-
-#ifdef emacs
-    BLOCK_INPUT;
-#endif
-
-    for (hp = last_alloca_header; hp != NULL;)
-      if ((STACK_DIR > 0 && hp->h.deep > depth)
-         || (STACK_DIR < 0 && hp->h.deep < depth))
-       {
-         register header *np = hp->h.next;
-
-         free ((pointer) hp);  /* Collect garbage.  */
-
-         hp = np;              /* -> next header.  */
-       }
-      else
-       break;                  /* Rest are not deeper.  */
-
-    last_alloca_header = hp;   /* -> last valid storage.  */
-
-#ifdef emacs
-    UNBLOCK_INPUT;
-#endif
-  }
-
-  if (size == 0)
-    return NULL;               /* No allocation required.  */
-
-  /* Allocate combined header + user data storage.  */
-
-  {
-    register pointer new = malloc (sizeof (header) + size);
-    /* Address of header.  */
-
-    ((header *) new)->h.next = last_alloca_header;
-    ((header *) new)->h.deep = depth;
-
-    last_alloca_header = (header *) new;
-
-    /* User storage begins just after header.  */
-
-    return (pointer) ((char *) new + sizeof (header));
-  }
-}
-
-#if defined (CRAY) && defined (CRAY_STACKSEG_END)
-
-#ifdef DEBUG_I00AFUNC
-#include <stdio.h>
-#endif
-
-#ifndef CRAY_STACK
-#define CRAY_STACK
-#ifndef CRAY2
-/* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */
-struct stack_control_header
-  {
-    long shgrow:32;            /* Number of times stack has grown.  */
-    long shaseg:32;            /* Size of increments to stack.  */
-    long shhwm:32;             /* High water mark of stack.  */
-    long shsize:32;            /* Current size of stack (all segments).  */
-  };
-
-/* The stack segment linkage control information occurs at
-   the high-address end of a stack segment.  (The stack
-   grows from low addresses to high addresses.)  The initial
-   part of the stack segment linkage control information is
-   0200 (octal) words.  This provides for register storage
-   for the routine which overflows the stack.  */
-
-struct stack_segment_linkage
-  {
-    long ss[0200];             /* 0200 overflow words.  */
-    long sssize:32;            /* Number of words in this segment.  */
-    long ssbase:32;            /* Offset to stack base.  */
-    long:32;
-    long sspseg:32;            /* Offset to linkage control of previous
-                                  segment of stack.  */
-    long:32;
-    long sstcpt:32;            /* Pointer to task common address block.  */
-    long sscsnm;               /* Private control structure number for
-                                  microtasking.  */
-    long ssusr1;               /* Reserved for user.  */
-    long ssusr2;               /* Reserved for user.  */
-    long sstpid;               /* Process ID for pid based multi-tasking.  */
-    long ssgvup;               /* Pointer to multitasking thread giveup.  */
-    long sscray[7];            /* Reserved for Cray Research.  */
-    long ssa0;
-    long ssa1;
-    long ssa2;
-    long ssa3;
-    long ssa4;
-    long ssa5;
-    long ssa6;
-    long ssa7;
-    long sss0;
-    long sss1;
-    long sss2;
-    long sss3;
-    long sss4;
-    long sss5;
-    long sss6;
-    long sss7;
-  };
-
-#else /* CRAY2 */
-/* The following structure defines the vector of words
-   returned by the STKSTAT library routine.  */
-struct stk_stat
-  {
-    long now;                  /* Current total stack size.  */
-    long maxc;                 /* Amount of contiguous space which would
-                                  be required to satisfy the maximum
-                                  stack demand to date.  */
-    long high_water;           /* Stack high-water mark.  */
-    long overflows;            /* Number of stack overflow ($STKOFEN) calls.  
*/
-    long hits;                 /* Number of internal buffer hits.  */
-    long extends;              /* Number of block extensions.  */
-    long stko_mallocs;         /* Block allocations by $STKOFEN.  */
-    long underflows;           /* Number of stack underflow calls ($STKRETN).  
*/
-    long stko_free;            /* Number of deallocations by $STKRETN.  */
-    long stkm_free;            /* Number of deallocations by $STKMRET.  */
-    long segments;             /* Current number of stack segments.  */
-    long maxs;                 /* Maximum number of stack segments so far.  */
-    long pad_size;             /* Stack pad size.  */
-    long current_address;      /* Current stack segment address.  */
-    long current_size;         /* Current stack segment size.  This
-                                  number is actually corrupted by STKSTAT to
-                                  include the fifteen word trailer area.  */
-    long initial_address;      /* Address of initial segment.  */
-    long initial_size;         /* Size of initial segment.  */
-  };
-
-/* The following structure describes the data structure which trails
-   any stack segment.  I think that the description in 'asdef' is
-   out of date.  I only describe the parts that I am sure about.  */
-
-struct stk_trailer
-  {
-    long this_address;         /* Address of this block.  */
-    long this_size;            /* Size of this block (does not include
-                                  this trailer).  */
-    long unknown2;
-    long unknown3;
-    long link;                 /* Address of trailer block of previous
-                                  segment.  */
-    long unknown5;
-    long unknown6;
-    long unknown7;
-    long unknown8;
-    long unknown9;
-    long unknown10;
-    long unknown11;
-    long unknown12;
-    long unknown13;
-    long unknown14;
-  };
-
-#endif /* CRAY2 */
-#endif /* not CRAY_STACK */
-
-#ifdef CRAY2
-/* Determine a "stack measure" for an arbitrary ADDRESS.
-   I doubt that "lint" will like this much. */
-
-static long
-i00afunc (long *address)
-{
-  struct stk_stat status;
-  struct stk_trailer *trailer;
-  long *block, size;
-  long result = 0;
-
-  /* We want to iterate through all of the segments.  The first
-     step is to get the stack status structure.  We could do this
-     more quickly and more directly, perhaps, by referencing the
-     $LM00 common block, but I know that this works.  */
-
-  STKSTAT (&status);
-
-  /* Set up the iteration.  */
-
-  trailer = (struct stk_trailer *) (status.current_address
-                                   + status.current_size
-                                   - 15);
-
-  /* There must be at least one stack segment.  Therefore it is
-     a fatal error if "trailer" is null.  */
-
-  if (trailer == 0)
-    abort ();
-
-  /* Discard segments that do not contain our argument address.  */
-
-  while (trailer != 0)
-    {
-      block = (long *) trailer->this_address;
-      size = trailer->this_size;
-      if (block == 0 || size == 0)
-       abort ();
-      trailer = (struct stk_trailer *) trailer->link;
-      if ((block <= address) && (address < (block + size)))
-       break;
-    }
-
-  /* Set the result to the offset in this segment and add the sizes
-     of all predecessor segments.  */
-
-  result = address - block;
-
-  if (trailer == 0)
-    {
-      return result;
-    }
-
-  do
-    {
-      if (trailer->this_size <= 0)
-       abort ();
-      result += trailer->this_size;
-      trailer = (struct stk_trailer *) trailer->link;
-    }
-  while (trailer != 0);
-
-  /* We are done.  Note that if you present a bogus address (one
-     not in any segment), you will get a different number back, formed
-     from subtracting the address of the first block.  This is probably
-     not what you want.  */
-
-  return (result);
-}
-
-#else /* not CRAY2 */
-/* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP.
-   Determine the number of the cell within the stack,
-   given the address of the cell.  The purpose of this
-   routine is to linearize, in some sense, stack addresses
-   for alloca.  */
-
-static long
-i00afunc (long address)
-{
-  long stkl = 0;
-
-  long size, pseg, this_segment, stack;
-  long result = 0;
-
-  struct stack_segment_linkage *ssptr;
-
-  /* Register B67 contains the address of the end of the
-     current stack segment.  If you (as a subprogram) store
-     your registers on the stack and find that you are past
-     the contents of B67, you have overflowed the segment.
-
-     B67 also points to the stack segment linkage control
-     area, which is what we are really interested in.  */
-
-  stkl = CRAY_STACKSEG_END ();
-  ssptr = (struct stack_segment_linkage *) stkl;
-
-  /* If one subtracts 'size' from the end of the segment,
-     one has the address of the first word of the segment.
-
-     If this is not the first segment, 'pseg' will be
-     nonzero.  */
-
-  pseg = ssptr->sspseg;
-  size = ssptr->sssize;
-
-  this_segment = stkl - size;
-
-  /* It is possible that calling this routine itself caused
-     a stack overflow.  Discard stack segments which do not
-     contain the target address.  */
-
-  while (!(this_segment <= address && address <= stkl))
-    {
-#ifdef DEBUG_I00AFUNC
-      fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl);
-#endif
-      if (pseg == 0)
-       break;
-      stkl = stkl - pseg;
-      ssptr = (struct stack_segment_linkage *) stkl;
-      size = ssptr->sssize;
-      pseg = ssptr->sspseg;
-      this_segment = stkl - size;
-    }
-
-  result = address - this_segment;
-
-  /* If you subtract pseg from the current end of the stack,
-     you get the address of the previous stack segment's end.
-     This seems a little convoluted to me, but I'll bet you save
-     a cycle somewhere.  */
-
-  while (pseg != 0)
-    {
-#ifdef DEBUG_I00AFUNC
-      fprintf (stderr, "%011o %011o\n", pseg, size);
-#endif
-      stkl = stkl - pseg;
-      ssptr = (struct stack_segment_linkage *) stkl;
-      size = ssptr->sssize;
-      pseg = ssptr->sspseg;
-      result += size;
-    }
-  return (result);
-}
-
-#endif /* not CRAY2 */
-#endif /* CRAY */
-
-#endif /* no alloca */
-#endif /* not GCC version 2 */