gas/subsegs.h

   1 /* subsegs.h -> subsegs.c
   2    Copyright (C) 1987 Free Software Foundation, Inc.
   3
   4 This file is part of GAS, the GNU Assembler.
   5
   6 GAS is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 1, or (at your option)
   9 any later version.
  10
  11 GAS is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GAS; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /*
  21  * For every sub-segment the user mentions in the ASsembler program,
  22  * we make one struct frchain. Each sub-segment has exactly one struct frchain
  23  * and vice versa.
  24  *
  25  * Struct frchain's are forward chained (in ascending order of sub-segment
  26  * code number). The chain runs through frch_next of each subsegment.
  27  * This makes it hard to find a subsegment's frags
  28  * if programmer uses a lot of them. Most programs only use text0 and
  29  * data0, so they don't suffer. At least this way:
  30  * (1)  There are no "arbitrary" restrictions on how many subsegments
  31  *      can be programmed;
  32  * (2)  Subsegments' frchain-s are (later) chained together in the order in
  33  *      which they are emitted for object file viz text then data.
  34  *
  35  * From each struct frchain dangles a chain of struct frags. The frags
  36  * represent code fragments, for that sub-segment, forward chained.
  37  */
  38
  39 struct frchain                  /* control building of a frag chain */
  40 {                               /* FRCH = FRagment CHain control */
  41   struct frag * frch_root;      /* 1st struct frag in chain, or NULL */
  42   struct frag * frch_last;      /* last struct frag in chain, or NULL */
  43   struct frchain * frch_next;   /* next in chain of struct frchain-s */
  44   segT          frch_seg;       /* SEG_TEXT or SEG_DATA. */
  45   subsegT       frch_subseg;    /* subsegment number of this chain */
  46 };
  47
  48 typedef struct frchain frchainS;
  49
  50 extern frchainS * frchain_root; /* NULL means no frchains yet. */
  51                                 /* all subsegments' chains hang off here */
  52
  53 extern frchainS * frchain_now;
  54                                 /* Frchain we are assembling into now */
  55                                 /* That is, the current segment's frag */
  56                                 /* chain, even if it contains no (complete) */
  57                                 /* frags. */
  58
  59 extern frchainS * data0_frchainP;
  60                                 /* Sentinel for frchain crawling. */
  61                                 /* Points to the 1st data-segment frchain. */
  62                                 /* (Which is pointed to by the last text- */
  63                                 /* segment frchain.) */
  64
  65 /* end: subsegs.h */