#include "complain.h"
#include "closure.h"
#include "LR0.h"
+#include "lalr.h"
#include "reduce.h"
int nstates;
int final_state;
-state_t *first_state = NULL;
-shifts *first_shift = NULL;
-reductions *first_reduction = NULL;
+static state_t *first_state = NULL;
+static shifts *first_shift = NULL;
static state_t *this_state = NULL;
static state_t *last_state = NULL;
static shifts *last_shift = NULL;
-static reductions *last_reduction = NULL;
static int nshifts;
static short *shift_symbol = NULL;
shifts *p = shifts_new (nshifts);
p->number = this_state->number;
-
shortcpy (p->shifts, shiftset, nshifts);
+ this_state->shifts = p;
if (last_shift)
last_shift->next = p;
/*------------------------------------------------------------------.
| Subroutine of augment_automaton. Create the next-to-final state, |
| to which a shift has already been made in the initial state. |
+| |
+| The task of this state consists in shifting (actually, it's a |
+| goto, but shifts and gotos are both stored in SHIFTS) the start |
+| symbols, hence the name. |
`------------------------------------------------------------------*/
static void
-insert_start_shift (void)
+insert_start_shifting_state (void)
{
state_t *statep;
shifts *sp;
statep = STATE_ALLOC (0);
statep->number = nstates;
+
+ /* The distinctive feature of this state from the
+ eof_shifting_state, is that it is labeled as post-start-symbol
+ shifting. I fail to understand why this state, and the
+ post-start-start can't be merged into one. But it does fail if
+ you try. --akim */
statep->accessing_symbol = start_symbol;
last_state->next = statep;
/* Make a shift from this state to (what will be) the final state. */
sp = shifts_new (1);
+ statep->shifts = sp;
sp->number = nstates++;
sp->shifts[0] = nstates;
}
+/*-----------------------------------------------------------------.
+| Subroutine of augment_automaton. Create the final state, which |
+| shifts `0', the end of file. The initial state shifts the start |
+| symbol, and goes to here. |
+`-----------------------------------------------------------------*/
+
+static void
+insert_eof_shifting_state (void)
+{
+ state_t *statep;
+ shifts *sp;
+
+ /* Make the final state--the one that follows a shift from the
+ next-to-final state.
+ The symbol for that shift is 0 (end-of-file). */
+ statep = STATE_ALLOC (0);
+ statep->number = nstates;
+
+ last_state->next = statep;
+ last_state = statep;
+
+ /* Make the shift from the final state to the termination state. */
+ sp = shifts_new (1);
+ statep->shifts = sp;
+ sp->number = nstates++;
+ sp->shifts[0] = nstates;
+
+ last_shift->next = sp;
+ last_shift = sp;
+}
+
+
+/*---------------------------------------------------------------.
+| Subroutine of augment_automaton. Create the accepting state. |
+`---------------------------------------------------------------*/
+
+static void
+insert_accepting_state (void)
+{
+ state_t *statep;
+
+ /* Note that the variable `final_state' refers to what we sometimes
+ call the termination state. */
+ final_state = nstates;
+
+ /* Make the termination state. */
+ statep = STATE_ALLOC (0);
+ statep->number = nstates++;
+ last_state->next = statep;
+ last_state = statep;
+}
+
+
+
+
+
/*------------------------------------------------------------------.
| Make sure that the initial state has a shift that accepts the |
| grammar's start symbol and goes to the next-to-final state, which |
static void
augment_automaton (void)
{
- state_t *statep;
- shifts *sp;
- shifts *sp1 = NULL;
-
- sp = first_shift;
-
- if (!sp->nshifts)
+ if (!first_state->shifts->nshifts)
{
- /* There are no shifts for any state. Make one shift, from the
+ /* The first state has no shifts. Make one shift, from the
initial state to the next-to-final state. */
- sp = shifts_new (1);
+ shifts *sp = shifts_new (1);
+ first_state->shifts = sp;
sp->shifts[0] = nstates;
/* Initialize the chain of shifts with sp. */
/* Create the next-to-final state, with shift to
what will be the final state. */
- insert_start_shift ();
+ insert_start_shifting_state ();
}
- else if (sp->number == 0)
+ else
{
- statep = first_state->next;
-
+ state_t *statep = first_state->next;
+ shifts *sp = first_state->shifts;
+ shifts *sp1 = NULL;
/* The states reached by shifts from FIRST_STATE are numbered
- 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL. */
- while (statep->accessing_symbol < start_symbol
+ 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL.
+ This is typical of `start: start ... ;': there is a state
+ with the item `start: start . ...'. We want to add a `shift
+ on EOF to eof-shifting state here. */
+ while (statep->accessing_symbol != start_symbol
&& statep->number < sp->nshifts)
statep = statep->next;
if (statep->accessing_symbol == start_symbol)
{
- /* We already have a next-to-final state.
- Make sure it has a shift to what will be the final state. */
+ /* We already have a next-to-final state, i.e., for `start:
+ start . ...'. Make sure it has a shift to what will be
+ the final state. */
while (sp && sp->number < statep->number)
{
sp1 = sp;
int i;
shifts *sp2 = shifts_new (sp->nshifts + 1);
sp2->number = statep->number;
+ statep->shifts = sp2;
sp2->shifts[0] = nstates;
for (i = sp->nshifts; i > 0; i--)
sp2->shifts[i] = sp->shifts[i - 1];
{
shifts *sp2 = shifts_new (1);
sp2->number = statep->number;
+ statep->shifts = sp2;
sp2->shifts[0] = nstates;
/* Patch sp2 into the chain of shifts between sp1 and sp. */
if (sp == 0)
last_shift = sp2;
}
+ insert_eof_shifting_state ();
}
else
{
+ /* There is no state for `start: start . ...'. */
int i, k;
shifts *sp2;
+ sp = first_shift;
/* There is no next-to-final state as yet. */
/* Add one more shift in first_shift,
going to the next-to-final state (yet to be made). */
- sp = first_shift;
-
sp2 = shifts_new (sp->nshifts + 1);
-
+ first_state->shifts = sp2;
/* Stick this shift into the vector at the proper place. */
statep = first_state->next;
for (k = 0, i = 0; i < sp->nshifts; k++, i++)
XFREE (sp);
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shift ();
+ /* Create the next-to-final state, with shift to what will
+ be the final state. Corresponds to `start: start . ...'. */
+ insert_start_shifting_state ();
}
}
- else
- {
- /* The initial state didn't even have any shifts.
- Give it one shift, to the next-to-final state. */
- sp = shifts_new (1);
- sp->shifts[0] = nstates;
-
- /* Patch sp into the chain of shifts at the beginning. */
- sp->next = first_shift;
- first_shift = sp;
-
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shift ();
- }
-
- /* Make the final state--the one that follows a shift from the
- next-to-final state.
- The symbol for that shift is 0 (end-of-file). */
- statep = STATE_ALLOC (0);
- statep->number = nstates;
- last_state->next = statep;
- last_state = statep;
-
- /* Make the shift from the final state to the termination state. */
- sp = shifts_new (1);
- sp->number = nstates++;
- sp->shifts[0] = nstates;
- last_shift->next = sp;
- last_shift = sp;
-
- /* Note that the variable `final_state' refers to what we sometimes call
- the termination state. */
- final_state = nstates;
- /* Make the termination state. */
- statep = STATE_ALLOC (0);
- statep->number = nstates++;
- last_state->next = statep;
- last_state = statep;
+ insert_accepting_state ();
}
if (count)
{
reductions *p = REDUCTIONS_ALLOC (count);
-
- p->number = this_state->number;
p->nreds = count;
-
shortcpy (p->rules, redset, count);
- if (last_reduction)
- last_reduction->next = p;
- else
- first_reduction = p;
- last_reduction = p;
+ this_state->reductions = p;
}
}
\f
+/*--------------------.
+| Build STATE_TABLE. |
+`--------------------*/
+
+static void
+set_state_table (void)
+{
+ /* NSTATES + 1 because lookahead for the pseudo state number NSTATES
+ might be used (see conflicts.c). It is too opaque for me to
+ provide a probably less hacky implementation. --akim */
+ state_table = XCALLOC (state_t *, nstates + 1);
+
+ {
+ state_t *sp;
+ for (sp = first_state; sp; sp = sp->next)
+ state_table[sp->number] = sp;
+ }
+
+ /* Pessimization, but simplification of the code: make sure all the
+ states have a shifts, even if reduced to 0 shifts. */
+ {
+ int i;
+ for (i = 0; i < nstates; i++)
+ if (!state_table[i]->shifts)
+ state_table[i]->shifts = shifts_new (0);
+ }
+
+ /* Initializing the lookaheads members. Please note that it must be
+ performed after having set some of the other members which are
+ used below. Change with extreme caution. */
+ {
+ int i;
+ int count = 0;
+ for (i = 0; i < nstates; i++)
+ {
+ int k;
+ reductions *rp = state_table[i]->reductions;
+ shifts *sp = state_table[i]->shifts;
+
+ state_table[i]->lookaheads = count;
+
+ if (rp
+ && (rp->nreds > 1 || (sp->nshifts && SHIFT_IS_SHIFT (sp, 0))))
+ count += rp->nreds;
+ else
+ state_table[i]->consistent = 1;
+
+ for (k = 0; k < sp->nshifts; k++)
+ if (SHIFT_IS_ERROR (sp, k))
+ {
+ state_table[i]->consistent = 0;
+ break;
+ }
+ }
+
+ /* Seems to be needed by conflicts.c. */
+ state_table[nstates] = STATE_ALLOC (0);
+ state_table[nstates]->lookaheads = count;
+ }
+}
+
/*-------------------------------------------------------------------.
| Compute the nondeterministic finite state machine (see state.h for |
| details) from the grammar. |
/* set up initial and final states as parser wants them */
augment_automaton ();
+
+ /* Set up STATE_TABLE. */
+ set_state_table ();
}
projects / bison.git / blobdiff