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+/* subsegs.h -> subsegs.c
+ Copyright (C) 1987 Free Software Foundation, Inc.
+
+This file is part of GAS, the GNU Assembler.
+
+GAS is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 1, or (at your option)
+any later version.
+
+GAS is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GAS; see the file COPYING. If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+/*
+ * For every sub-segment the user mentions in the ASsembler program,
+ * we make one struct frchain. Each sub-segment has exactly one struct frchain
+ * and vice versa.
+ *
+ * Struct frchain's are forward chained (in ascending order of sub-segment
+ * code number). The chain runs through frch_next of each subsegment.
+ * This makes it hard to find a subsegment's frags
+ * if programmer uses a lot of them. Most programs only use text0 and
+ * data0, so they don't suffer. At least this way:
+ * (1) There are no "arbitrary" restrictions on how many subsegments
+ * can be programmed;
+ * (2) Subsegments' frchain-s are (later) chained together in the order in
+ * which they are emitted for object file viz text then data.
+ *
+ * From each struct frchain dangles a chain of struct frags. The frags
+ * represent code fragments, for that sub-segment, forward chained.
+ */
+
+struct frchain /* control building of a frag chain */
+{ /* FRCH = FRagment CHain control */
+ struct frag * frch_root; /* 1st struct frag in chain, or NULL */
+ struct frag * frch_last; /* last struct frag in chain, or NULL */
+ struct frchain * frch_next; /* next in chain of struct frchain-s */
+ segT frch_seg; /* SEG_TEXT or SEG_DATA. */
+ subsegT frch_subseg; /* subsegment number of this chain */
+};
+
+typedef struct frchain frchainS;
+
+extern frchainS * frchain_root; /* NULL means no frchains yet. */
+ /* all subsegments' chains hang off here */
+
+extern frchainS * frchain_now;
+ /* Frchain we are assembling into now */
+ /* That is, the current segment's frag */
+ /* chain, even if it contains no (complete) */
+ /* frags. */
+
+extern frchainS * data0_frchainP;
+ /* Sentinel for frchain crawling. */
+ /* Points to the 1st data-segment frchain. */
+ /* (Which is pointed to by the last text- */
+ /* segment frchain.) */
+
+/* end: subsegs.h */