X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0fb669f9d648dfdd7a39478a6b658511455ae966..94ebeba53ffd20afbc5d0c9caa3c80c40e910e4c:/src/lalr.c diff --git a/src/lalr.c b/src/lalr.c index 8627f1cb..f2bfa967 100644 --- a/src/lalr.c +++ b/src/lalr.c @@ -1,7 +1,7 @@ -/* Compute look-ahead criteria for Bison. +/* Compute lookahead criteria for Bison. - Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004 - Free Software Foundation, Inc. + Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005, + 2006 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. @@ -22,9 +22,10 @@ /* Compute how to make the finite state machine deterministic; find - which rules need look-ahead in each state, and which look-ahead + which rules need lookahead in each state, and which lookahead tokens they accept. */ +#include #include "system.h" #include @@ -93,8 +94,7 @@ set_goto_map (void) ngotos++; /* Abort if (ngotos + 1) would overflow. */ - if (ngotos == GOTO_NUMBER_MAXIMUM) - abort (); + aver (ngotos != GOTO_NUMBER_MAXIMUM); goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++; } @@ -153,8 +153,7 @@ map_goto (state_number s0, symbol_number sym) for (;;) { - if (high < low) - abort (); + aver (low <= high); middle = (low + high) / 2; s = from_state[middle]; if (s == s0) @@ -220,9 +219,9 @@ add_lookback_edge (state *s, rule *r, goto_number gotono) { int ri = state_reduction_find (s, r); goto_list *sp = xmalloc (sizeof *sp); - sp->next = lookback[(s->reductions->look_ahead_tokens - LA) + ri]; + sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri]; sp->value = gotono; - lookback[(s->reductions->look_ahead_tokens - LA) + ri] = sp; + lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp; } @@ -246,11 +245,11 @@ build_relations (void) { bool done; int length = 1; - item_number *rp; + item_number const *rp; state *s = states[from_state[i]]; states1[0] = s->number; - for (rp = (*rulep)->rhs; *rp >= 0; rp++) + for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++) { s = transitions_to (s->transitions, item_number_as_symbol_number (*rp)); @@ -265,9 +264,11 @@ build_relations (void) while (!done) { done = true; + /* Each rhs ends in an item number, and there is a + sentinel before the first rhs, so it is safe to + decrement RP here. */ rp--; - /* JF added rp>=ritem && I hope to god its right! */ - if (rp >= ritem && ISVAR (*rp)) + if (ISVAR (*rp)) { /* Downcasting from item_number to symbol_number. */ edge[nedges++] = map_goto (states1[--length], @@ -313,7 +314,7 @@ compute_FOLLOWS (void) static void -compute_look_ahead_tokens (void) +compute_lookahead_tokens (void) { size_t i; goto_list *sp; @@ -331,27 +332,27 @@ compute_look_ahead_tokens (void) } -/*-----------------------------------------------------. -| Count the number of look-ahead tokens required for S | -| (N_LOOK_AHEAD_TOKENS member). | -`-----------------------------------------------------*/ +/*----------------------------------------------------. +| Count the number of lookahead tokens required for S | +| (N_LOOKAHEAD_TOKENS member). | +`----------------------------------------------------*/ static int -state_look_ahead_tokens_count (state *s) +state_lookahead_tokens_count (state *s) { int k; - int n_look_ahead_tokens = 0; + int n_lookahead_tokens = 0; reductions *rp = s->reductions; transitions *sp = s->transitions; - /* We need a look-ahead either to distinguish different + /* We need a lookahead either to distinguish different reductions (i.e., there are two or more), or to distinguish a reduction from a shift. Otherwise, it is straightforward, and the state is `consistent'. */ if (rp->num > 1 || (rp->num == 1 && sp->num && !TRANSITION_IS_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0))) - n_look_ahead_tokens += rp->num; + n_lookahead_tokens += rp->num; else s->consistent = 1; @@ -362,13 +363,13 @@ state_look_ahead_tokens_count (state *s) break; } - return n_look_ahead_tokens; + return n_lookahead_tokens; } -/*-----------------------------------------------------. -| Compute LA, NLA, and the look_ahead_tokens members. | -`-----------------------------------------------------*/ +/*----------------------------------------------------. +| Compute LA, NLA, and the lookahead_tokens members. | +`----------------------------------------------------*/ static void initialize_LA (void) @@ -376,10 +377,10 @@ initialize_LA (void) state_number i; bitsetv pLA; - /* Compute the total number of reductions requiring a look-ahead. */ + /* Compute the total number of reductions requiring a lookahead. */ nLA = 0; for (i = 0; i < nstates; i++) - nLA += state_look_ahead_tokens_count (states[i]); + nLA += state_lookahead_tokens_count (states[i]); /* Avoid having to special case 0. */ if (!nLA) nLA = 1; @@ -387,54 +388,54 @@ initialize_LA (void) pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED); lookback = xcalloc (nLA, sizeof *lookback); - /* Initialize the members LOOK_AHEAD_TOKENS for each state whose reductions - require look-ahead tokens. */ + /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions + require lookahead tokens. */ for (i = 0; i < nstates; i++) { - int count = state_look_ahead_tokens_count (states[i]); + int count = state_lookahead_tokens_count (states[i]); if (count) { - states[i]->reductions->look_ahead_tokens = pLA; + states[i]->reductions->lookahead_tokens = pLA; pLA += count; } } } -/*----------------------------------------------. -| Output the look-ahead tokens for each state. | -`----------------------------------------------*/ +/*---------------------------------------------. +| Output the lookahead tokens for each state. | +`---------------------------------------------*/ static void -look_ahead_tokens_print (FILE *out) +lookahead_tokens_print (FILE *out) { state_number i; int j, k; - fprintf (out, "Look-ahead tokens: BEGIN\n"); + fprintf (out, "Lookahead tokens: BEGIN\n"); for (i = 0; i < nstates; ++i) { reductions *reds = states[i]->reductions; bitset_iterator iter; - int n_look_ahead_tokens = 0; + int n_lookahead_tokens = 0; - if (reds->look_ahead_tokens) + if (reds->lookahead_tokens) for (k = 0; k < reds->num; ++k) - if (reds->look_ahead_tokens[k]) - ++n_look_ahead_tokens; + if (reds->lookahead_tokens[k]) + ++n_lookahead_tokens; - fprintf (out, "State %d: %d look-ahead tokens\n", - i, n_look_ahead_tokens); + fprintf (out, "State %d: %d lookahead tokens\n", + i, n_lookahead_tokens); - if (reds->look_ahead_tokens) + if (reds->lookahead_tokens) for (j = 0; j < reds->num; ++j) - BITSET_FOR_EACH (iter, reds->look_ahead_tokens[j], k, 0) + BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0) { fprintf (out, " on %d (%s) -> rule %d\n", k, symbols[k]->tag, reds->rules[j]->number); }; } - fprintf (out, "Look-ahead tokens: END\n"); + fprintf (out, "Lookahead tokens: END\n"); } void @@ -445,10 +446,10 @@ lalr (void) initialize_F (); build_relations (); compute_FOLLOWS (); - compute_look_ahead_tokens (); + compute_lookahead_tokens (); if (trace_flag & trace_sets) - look_ahead_tokens_print (stderr); + lookahead_tokens_print (stderr); } @@ -457,6 +458,6 @@ lalr_free (void) { state_number s; for (s = 0; s < nstates; ++s) - states[s]->reductions->look_ahead_tokens = NULL; + states[s]->reductions->lookahead_tokens = NULL; bitsetv_free (LA); }