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) 2004-2013 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
  11 (at 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 <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23
  24 #include "lisp.h"
  25
  26 #include <unistd.h>
  27
  28 #define STATIC_HEAP_SIZE        (13 * 1024 * 1024)
  29
  30 int debug_sheap = 0;
  31
  32 #define BLOCKSIZE 4096
  33
  34 char bss_sbrk_buffer[STATIC_HEAP_SIZE];
  35 char *bss_sbrk_ptr;
  36 int bss_sbrk_did_unexec;
  37
  38 void *
  39 bss_sbrk (ptrdiff_t request_size)
  40 {
  41   if (!bss_sbrk_ptr)
  42     {
  43       bss_sbrk_ptr = bss_sbrk_buffer;
  44 #ifdef CYGWIN
  45       sbrk (BLOCKSIZE);         /* force space for fork to work */
  46 #endif
  47     }
  48
  49   if (!(int) request_size)
  50     {
  51       return (bss_sbrk_ptr);
  52     }
  53   else if (bss_sbrk_ptr + (int) request_size < bss_sbrk_buffer)
  54     {
  55       printf
  56         ("attempt to free too much: avail %d used %d failed request %d\n",
  57          STATIC_HEAP_SIZE, bss_sbrk_ptr - bss_sbrk_buffer,
  58          (int) request_size);
  59       exit (-1);
  60       return 0;
  61     }
  62   else if (bss_sbrk_ptr + (int) request_size >
  63            bss_sbrk_buffer + STATIC_HEAP_SIZE)
  64     {
  65       printf ("static heap exhausted: avail %d used %d failed request %d\n",
  66               STATIC_HEAP_SIZE,
  67               bss_sbrk_ptr - bss_sbrk_buffer, (int) request_size);
  68       exit (-1);
  69       return 0;
  70     }
  71   else if ((int) request_size < 0)
  72     {
  73       bss_sbrk_ptr += (int) request_size;
  74       if (debug_sheap)
  75         printf ("freed size %d\n", request_size);
  76       return bss_sbrk_ptr;
  77     }
  78   else
  79     {
  80       char *ret = bss_sbrk_ptr;
  81       if (debug_sheap)
  82         printf ("allocated 0x%08x size %d\n", ret, request_size);
  83       bss_sbrk_ptr += (int) request_size;
  84       return ret;
  85     }
  86 }
  87
  88 void
  89 report_sheap_usage (int die_if_pure_storage_exceeded)
  90 {
  91   char buf[200];
  92   sprintf (buf, "Static heap usage: %d of %d bytes",
  93            bss_sbrk_ptr - bss_sbrk_buffer, STATIC_HEAP_SIZE);
  94   message ("%s", buf);
  95 }