src/sheap.c

   1 /* simulate `sbrk' with an array in .bss, for `unexec' support for Cygwin;
   2    complete rewrite of xemacs Cygwin `unexec' code
   3
   4    Copyright (C) 2004-2018 Free Software Foundation, Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or (at
  11 your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22
  23 #include "sheap.h"
  24
  25 #include <stdio.h>
  26 #include "lisp.h"
  27 #include <unistd.h>
  28 #include <stdlib.h>             /* for exit */
  29
  30 static int debug_sheap;
  31
  32 char bss_sbrk_buffer[STATIC_HEAP_SIZE];
  33 char *max_bss_sbrk_ptr;
  34 bool bss_sbrk_did_unexec;
  35
  36 void *
  37 bss_sbrk (ptrdiff_t request_size)
  38 {
  39   static char *bss_sbrk_ptr;
  40
  41   if (!bss_sbrk_ptr)
  42     {
  43       max_bss_sbrk_ptr = bss_sbrk_ptr = bss_sbrk_buffer;
  44 #ifdef CYGWIN
  45       /* Force space for fork to work.  */
  46       sbrk (4096);
  47 #endif
  48     }
  49
  50   int used = bss_sbrk_ptr - bss_sbrk_buffer;
  51
  52   if (request_size < -used)
  53     {
  54       printf (("attempt to free too much: "
  55                "avail %d used %d failed request %"pD"d\n"),
  56               STATIC_HEAP_SIZE, used, request_size);
  57       exit (-1);
  58       return 0;
  59     }
  60   else if (STATIC_HEAP_SIZE - used < request_size)
  61     {
  62       printf ("static heap exhausted: avail %d used %d failed request %"pD"d\n",
  63               STATIC_HEAP_SIZE, used, request_size);
  64       exit (-1);
  65       return 0;
  66     }
  67
  68   void *ret = bss_sbrk_ptr;
  69   bss_sbrk_ptr += request_size;
  70   if (max_bss_sbrk_ptr < bss_sbrk_ptr)
  71     max_bss_sbrk_ptr = bss_sbrk_ptr;
  72   if (debug_sheap)
  73     {
  74       if (request_size < 0)
  75         printf ("freed size %"pD"d\n", request_size);
  76       else
  77         printf ("allocated %p size %"pD"d\n", ret, request_size);
  78     }
  79   return ret;
  80 }