xref: /freebsd-10.1-release/usr.bin/make/make.c

/*-
 * Copyright (c) 1988, 1989, 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1989 by Berkeley Softworks
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#)make.c	8.1 (Berkeley) 6/6/93
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * make.c
 *	The functions which perform the examination of targets and
 *	their suitability for creation
 *
 * Interface:
 *	Make_Run	Initialize things for the module and recreate
 *			whatever needs recreating. Returns TRUE if
 *			work was (or would have been) done and FALSE
 *			otherwise.
 *
 *	Make_Update	Update all parents of a given child. Performs
 *			various bookkeeping chores like the updating
 *			of the cmtime field of the parent, filling
 *			of the IMPSRC context variable, etc. It will
 *			place the parent on the toBeMade queue if it should be.
 *
 *	Make_TimeStamp	Function to set the parent's cmtime field
 *			based on a child's modification time.
 *
 *	Make_DoAllVar	Set up the various local variables for a
 *			target, including the .ALLSRC variable, making
 *			sure that any variable that needs to exist
 *			at the very least has the empty value.
 *
 *	Make_OODate	Determine if a target is out-of-date.
 *
 *	Make_HandleUse	See if a child is a .USE node for a parent
 *			and perform the .USE actions if so.
 */

#include "arch.h"
#include "config.h"
#include "dir.h"
#include "globals.h"
#include "GNode.h"
#include "job.h"
#include "make.h"
#include "parse.h"
#include "suff.h"
#include "targ.h"
#include "util.h"
#include "var.h"

/* The current fringe of the graph. These are nodes which await examination
 * by MakeOODate. It is added to by Make_Update and subtracted from by
 * MakeStartJobs */
static Lst toBeMade = Lst_Initializer(toBeMade);

/*
 * Number of nodes to be processed. If this is non-zero when Job_Empty()
 * returns TRUE, there's a cycle in the graph.
 */
static int numNodes;

static Boolean MakeStartJobs(void);

/**
 * Make_TimeStamp
 *	Set the cmtime field of a parent node based on the mtime stamp in its
 *	child. Called from MakeOODate via LST_FOREACH.
 *
 * Results:
 *	Always returns 0.
 *
 * Side Effects:
 *	The cmtime of the parent node will be changed if the mtime
 *	field of the child is greater than it.
 */
int
Make_TimeStamp(GNode *pgn, GNode *cgn)
{

	if (cgn->mtime > pgn->cmtime) {
		pgn->cmtime = cgn->mtime;
		pgn->cmtime_gn = cgn;
	}
	return (0);
}

/**
 * Make_OODate
 *	See if a given node is out of date with respect to its sources.
 *	Used by Make_Run when deciding which nodes to place on the
 *	toBeMade queue initially and by Make_Update to screen out USE and
 *	EXEC nodes. In the latter case, however, any other sort of node
 *	must be considered out-of-date since at least one of its children
 *	will have been recreated.
 *
 * Results:
 *	TRUE if the node is out of date. FALSE otherwise.
 *
 * Side Effects:
 *	The mtime field of the node and the cmtime field of its parents
 *	will/may be changed.
 */
Boolean
Make_OODate(GNode *gn)
{
	Boolean	oodate;
	LstNode	*ln;

	/*
	 * Certain types of targets needn't even be sought as their datedness
	 * doesn't depend on their modification time...
	 */
	if ((gn->type & (OP_JOIN | OP_USE | OP_EXEC)) == 0) {
		Dir_MTime(gn);
		if (gn->mtime != 0) {
			DEBUGF(MAKE, ("modified %s...",
			    Targ_FmtTime(gn->mtime)));
		} else {
			DEBUGF(MAKE, ("non-existent..."));
		}
	}

	/*
	 * A target is remade in one of the following circumstances:
	 *	its modification time is smaller than that of its youngest child
	 *	    and it would actually be run (has commands or type OP_NOP)
	 *	it's the object of a force operator
	 *	it has no children, was on the lhs of an operator and doesn't
	 *	    exist already.
	 *
	 * Libraries are only considered out-of-date if the archive module says
	 * they are.
	 *
	 * These weird rules are brought to you by Backward-Compatibility and
	 * the strange people who wrote 'Make'.
	 */
	if (gn->type & OP_USE) {
		/*
		 * If the node is a USE node it is *never* out of date
		 * no matter *what*.
		 */
		DEBUGF(MAKE, (".USE node..."));
		oodate = FALSE;

	} else if (gn->type & OP_LIB) {
		DEBUGF(MAKE, ("library..."));

		/*
		 * always out of date if no children and :: target
		 */
		oodate = Arch_LibOODate(gn) ||
		    ((gn->cmtime == 0) && (gn->type & OP_DOUBLEDEP));

	} else if (gn->type & OP_JOIN) {
		/*
		 * A target with the .JOIN attribute is only considered
		 * out-of-date if any of its children was out-of-date.
		 */
		DEBUGF(MAKE, (".JOIN node..."));
		oodate = gn->childMade;

	} else if (gn->type & (OP_FORCE|OP_EXEC|OP_PHONY)) {
		/*
		 * A node which is the object of the force (!) operator or
		 * which has the .EXEC attribute is always considered
		 * out-of-date.
		 */
		if (gn->type & OP_FORCE) {
			DEBUGF(MAKE, ("! operator..."));
		} else if (gn->type & OP_PHONY) {
			DEBUGF(MAKE, (".PHONY node..."));
		} else {
			DEBUGF(MAKE, (".EXEC node..."));
		}

		if (remakingMakefiles) {
			DEBUGF(MAKE, ("skipping (remaking makefiles)..."));
			oodate = FALSE;
		} else {
			oodate = TRUE;
		}
	} else if (gn->mtime < gn->cmtime ||
	    (gn->cmtime == 0 && (gn->mtime == 0 || (gn->type & OP_DOUBLEDEP)))) {
		/*
		 * A node whose modification time is less than that of its
		 * youngest child or that has no children (cmtime == 0) and
		 * either doesn't exist (mtime == 0) or was the object of a
		 * :: operator is out-of-date. Why? Because that's the way
		 * Make does it.
		 */
		if (gn->mtime < gn->cmtime) {
			DEBUGF(MAKE, ("modified before source (%s)...",
			    gn->cmtime_gn ? gn->cmtime_gn->path : "???"));
			oodate = TRUE;
		} else if (gn->mtime == 0) {
			DEBUGF(MAKE, ("non-existent and no sources..."));
			if (remakingMakefiles && Lst_IsEmpty(&gn->commands)) {
				DEBUGF(MAKE, ("skipping (no commands and remaking makefiles)..."));
				oodate = FALSE;
			} else {
				oodate = TRUE;
			}
		} else {
			DEBUGF(MAKE, (":: operator and no sources..."));
			if (remakingMakefiles) {
				DEBUGF(MAKE, ("skipping (remaking makefiles)..."));
				oodate = FALSE;
			} else {
				oodate = TRUE;
			}
		}
	} else
		oodate = FALSE;

	/*
	 * If the target isn't out-of-date, the parents need to know its
	 * modification time. Note that targets that appear to be out-of-date
	 * but aren't, because they have no commands and aren't of type OP_NOP,
	 * have their mtime stay below their children's mtime to keep parents
	 * from thinking they're out-of-date.
	 */
	if (!oodate) {
		LST_FOREACH(ln, &gn->parents)
			if (Make_TimeStamp(Lst_Datum(ln), gn))
				break;
	}

	return (oodate);
}

/**
 * Make_HandleUse
 *	Function called by Make_Run and SuffApplyTransform on the downward
 *	pass to handle .USE and transformation nodes. A callback function
 *	for LST_FOREACH, it implements the .USE and transformation
 *	functionality by copying the node's commands, type flags
 *	and children to the parent node. Should be called before the
 *	children are enqueued to be looked at.
 *
 *	A .USE node is much like an explicit transformation rule, except
 *	its commands are always added to the target node, even if the
 *	target already has commands.
 *
 * Results:
 *	returns 0.
 *
 * Side Effects:
 *	Children and commands may be added to the parent and the parent's
 *	type may be changed.
 *
 *-----------------------------------------------------------------------
 */
int
Make_HandleUse(GNode *cgn, GNode *pgn)
{
	GNode	*gn;	/* A child of the .USE node */
	LstNode	*ln;	/* An element in the children list */

	if (cgn->type & (OP_USE | OP_TRANSFORM)) {
		if ((cgn->type & OP_USE) || Lst_IsEmpty(&pgn->commands)) {
			/*
			 * .USE or transformation and target has no commands --
			 * append the child's commands to the parent.
			 */
			Lst_Concat(&pgn->commands, &cgn->commands, LST_CONCNEW);
		}

		for (ln = Lst_First(&cgn->children); ln != NULL;
		    ln = Lst_Succ(ln)) {
			gn = Lst_Datum(ln);

			if (Lst_Member(&pgn->children, gn) == NULL) {
				Lst_AtEnd(&pgn->children, gn);
				Lst_AtEnd(&gn->parents, pgn);
				pgn->unmade += 1;
			}
		}

		pgn->type |= cgn->type & ~(OP_OPMASK | OP_USE | OP_TRANSFORM);

		/*
		 * This child node is now "made", so we decrement the count of
		 * unmade children in the parent... We also remove the child
		 * from the parent's list to accurately reflect the number of
		 * decent children the parent has. This is used by Make_Run to
		 * decide whether to queue the parent or examine its children...
		 */
		if (cgn->type & OP_USE) {
			pgn->unmade--;
		}
	}
	return (0);
}

/**
 * Make_Update
 *	Perform update on the parents of a node. Used by JobFinish once
 *	a node has been dealt with and by MakeStartJobs if it finds an
 *	up-to-date node.
 *
 * Results:
 *	Always returns 0
 *
 * Side Effects:
 *	The unmade field of pgn is decremented and pgn may be placed on
 *	the toBeMade queue if this field becomes 0.
 *
 * 	If the child was made, the parent's childMade field will be set true
 *	and its cmtime set to now.
 *
 *	If the child wasn't made, the cmtime field of the parent will be
 *	altered if the child's mtime is big enough.
 *
 *	Finally, if the child is the implied source for the parent, the
 *	parent's IMPSRC variable is set appropriately.
 */
void
Make_Update(GNode *cgn)
{
	GNode		*pgn;	/* the parent node */
	const char	*cname;	/* the child's name */
	LstNode		*ln;	/* Element in parents and iParents lists */
	const char	*cpref;

	cname = Var_Value(TARGET, cgn);

	/*
	 * If the child was actually made, see what its modification time is
	 * now -- some rules won't actually update the file. If the file still
	 * doesn't exist, make its mtime now.
	 */
	if (cgn->made != UPTODATE) {
#ifndef RECHECK
		/*
		 * We can't re-stat the thing, but we can at least take care
		 * of rules where a target depends on a source that actually
		 * creates the target, but only if it has changed, e.g.
		 *
		 * parse.h : parse.o
		 *
		 * parse.o : parse.y
		 *  	yacc -d parse.y
		 *  	cc -c y.tab.c
		 *  	mv y.tab.o parse.o
		 *  	cmp -s y.tab.h parse.h || mv y.tab.h parse.h
		 *
		 * In this case, if the definitions produced by yacc haven't
		 * changed from before, parse.h won't have been updated and
		 * cgn->mtime will reflect the current modification time for
		 * parse.h. This is something of a kludge, I admit, but it's a
		 * useful one..
		 * XXX: People like to use a rule like
		 *
		 * FRC:
		 *
		 * To force things that depend on FRC to be made, so we have to
		 * check for gn->children being empty as well...
		 */
		if (!Lst_IsEmpty(&cgn->commands) ||
		    Lst_IsEmpty(&cgn->children)) {
			cgn->mtime = now;
		}
	#else
		/*
		 * This is what Make does and it's actually a good thing, as it
		 * allows rules like
		 *
		 *	cmp -s y.tab.h parse.h || cp y.tab.h parse.h
		 *
		 * to function as intended. Unfortunately, thanks to the
		 * stateless nature of NFS (by which I mean the loose coupling
		 * of two clients using the same file from a common server),
		 * there are times when the modification time of a file created
		 * on a remote machine will not be modified before the local
		 * stat() implied by the Dir_MTime occurs, thus leading us to
		 * believe that the file is unchanged, wreaking havoc with
		 * files that depend on this one.
		 *
		 * I have decided it is better to make too much than to make too
		 * little, so this stuff is commented out unless you're sure
		 * it's ok.
		 * -- ardeb 1/12/88
		 */
		/*
		 * Christos, 4/9/92: If we are  saving commands pretend that
		 * the target is made now. Otherwise archives with ... rules
		 * don't work!
		 */
		if (noExecute || (cgn->type & OP_SAVE_CMDS) ||
		    Dir_MTime(cgn) == 0) {
			cgn->mtime = now;
		}
		DEBUGF(MAKE, ("update time: %s\n", Targ_FmtTime(cgn->mtime)));
#endif
	}

	for (ln = Lst_First(&cgn->parents); ln != NULL; ln = Lst_Succ(ln)) {
		pgn = Lst_Datum(ln);
		if (pgn->make) {
			pgn->unmade -= 1;

			if (!(cgn->type & (OP_EXEC | OP_USE))) {
				if (cgn->made == MADE)
					pgn->childMade = TRUE;
				Make_TimeStamp(pgn, cgn);
			}
			if (pgn->unmade == 0) {
				/*
				 * Queue the node up -- any unmade predecessors
				 * will be dealt with in MakeStartJobs.
				 */
				Lst_EnQueue(&toBeMade, pgn);
			} else if (pgn->unmade < 0) {
				Error("Graph cycles through %s", pgn->name);
			}
		}
	}

	/*
	 * Deal with successor nodes. If any is marked for making and has an
	 * unmade count of 0, has not been made and isn't in the examination
	 * queue, it means we need to place it in the queue as it restrained
	 * itself before.
	 */
	for (ln = Lst_First(&cgn->successors); ln != NULL; ln = Lst_Succ(ln)) {
		GNode	*succ = Lst_Datum(ln);

		if (succ->make && succ->unmade == 0 && succ->made == UNMADE &&
		    Lst_Member(&toBeMade, succ) == NULL) {
			Lst_EnQueue(&toBeMade, succ);
		}
	}

	/*
	 * Set the .PREFIX and .IMPSRC variables for all the implied parents
	 * of this node.
	 */
	cpref = Var_Value(PREFIX, cgn);
	for (ln = Lst_First(&cgn->iParents); ln != NULL; ln = Lst_Succ(ln)) {
		pgn = Lst_Datum(ln);
		if (pgn->make) {
			Var_Set(IMPSRC, cname, pgn);
			Var_Set(PREFIX, cpref, pgn);
		}
	}
}

/**
 * Make_DoAllVar
 *	Set up the ALLSRC and OODATE variables. Sad to say, it must be
 *	done separately, rather than while traversing the graph. This is
 *	because Make defined OODATE to contain all sources whose modification
 *	times were later than that of the target, *not* those sources that
 *	were out-of-date. Since in both compatibility and native modes,
 *	the modification time of the parent isn't found until the child
 *	has been dealt with, we have to wait until now to fill in the
 *	variable. As for ALLSRC, the ordering is important and not
 *	guaranteed when in native mode, so it must be set here, too.
 *
 * Side Effects:
 *	The ALLSRC and OODATE variables of the given node is filled in.
 *	If the node is a .JOIN node, its TARGET variable will be set to
 * 	match its ALLSRC variable.
 */
void
Make_DoAllVar(GNode *gn)
{
	LstNode		*ln;
	GNode		*cgn;
	const char	*child;

	LST_FOREACH(ln, &gn->children) {
		/*
		 * Add the child's name to the ALLSRC and OODATE variables of
		 * the given node. The child is added only if it has not been
		 * given the .EXEC, .USE or .INVISIBLE attributes. .EXEC and
		 * .USE children are very rarely going to be files, so...
		 *
		 * A child is added to the OODATE variable if its modification
		 * time is later than that of its parent, as defined by Make,
		 * except if the parent is a .JOIN node. In that case, it is
		 * only added to the OODATE variable if it was actually made
		 * (since .JOIN nodes don't have modification times, the
		 * comparison is rather unfair...).
		 */
		cgn = Lst_Datum(ln);

		if ((cgn->type & (OP_EXEC | OP_USE | OP_INVISIBLE)) == 0) {
			if (OP_NOP(cgn->type)) {
				/*
				 * this node is only source; use the specific
				 * pathname for it
				 */
				child = cgn->path ? cgn->path : cgn->name;
			} else
				child = Var_Value(TARGET, cgn);
			Var_Append(ALLSRC, child, gn);
			if (gn->type & OP_JOIN) {
				if (cgn->made == MADE) {
					Var_Append(OODATE, child, gn);
				}
			} else if (gn->mtime < cgn->mtime ||
			    (cgn->mtime >= now && cgn->made == MADE)) {
				/*
				 * It goes in the OODATE variable if the parent
				 * is younger than the child or if the child has
				 * been modified more recently than the start of
				 * the make. This is to keep pmake from getting
				 * confused if something else updates the parent
				 * after the make starts (shouldn't happen, I
				 * know, but sometimes it does). In such a case,
				 * if we've updated the kid, the parent is
				 * likely to have a modification time later than
				 * that of the kid and anything that relies on
				 * the OODATE variable will be hosed.
				 *
				 * XXX: This will cause all made children to
				 * go in the OODATE variable, even if they're
				 * not touched, if RECHECK isn't defined, since
				 * cgn->mtime is set to now in Make_Update.
				 * According to some people, this is good...
				 */
				Var_Append(OODATE, child, gn);
			}
		}
	}

	if (!Var_Exists (OODATE, gn)) {
		Var_Set(OODATE, "", gn);
	}
	if (!Var_Exists (ALLSRC, gn)) {
		Var_Set(ALLSRC, "", gn);
	}

	if (gn->type & OP_JOIN) {
		Var_Set(TARGET, Var_Value(ALLSRC, gn), gn);
	}
}

/**
 * MakeStartJobs
 *	Start as many jobs as possible.
 *
 * Results:
 *	If the query flag was given to pmake, no job will be started,
 *	but as soon as an out-of-date target is found, this function
 *	returns TRUE. At all other times, this function returns FALSE.
 *
 * Side Effects:
 *	Nodes are removed from the toBeMade queue and job table slots
 *	are filled.
 */
static Boolean
MakeStartJobs(void)
{
	GNode	*gn;

	while (!Lst_IsEmpty(&toBeMade) && !Job_Full()) {
		gn = Lst_DeQueue(&toBeMade);
		DEBUGF(MAKE, ("Examining %s...", gn->name));

		/*
		 * Make sure any and all predecessors that are going to be made,
		 * have been.
		 */
		if (!Lst_IsEmpty(&gn->preds)) {
			LstNode *ln;

			for (ln = Lst_First(&gn->preds); ln != NULL;
			    ln = Lst_Succ(ln)){
				GNode	*pgn = Lst_Datum(ln);

				if (pgn->make && pgn->made == UNMADE) {
					DEBUGF(MAKE, ("predecessor %s not made "
					    "yet.\n", pgn->name));
					break;
				}
			}
			/*
			 * If ln isn't NULL, there's a predecessor as yet
			 * unmade, so we just drop this node on the floor.
			 * When the node in question has been made, it will
			 * notice this node as being ready to make but as yet
			 * unmade and will place the node on the queue.
			 */
			if (ln != NULL) {
				continue;
			}
		}

		numNodes--;
		if (Make_OODate(gn)) {
			DEBUGF(MAKE, ("out-of-date\n"));
			if (queryFlag) {
				return (TRUE);
			}
			Make_DoAllVar(gn);
			Job_Make(gn);
		} else {
			DEBUGF(MAKE, ("up-to-date\n"));
			gn->made = UPTODATE;
			if (gn->type & OP_JOIN) {
				/*
				 * Even for an up-to-date .JOIN node, we need
				 * it to have its context variables so
				 * references to it get the correct value for
				 * .TARGET when building up the context
				 * variables of its parent(s)...
				 */
				Make_DoAllVar(gn);
			}

			Make_Update(gn);
		}
	}
	return (FALSE);
}

/**
 * MakePrintStatus
 *	Print the status of a top-level node, viz. it being up-to-date
 *	already or not created due to an error in a lower level.
 *	Callback function for Make_Run via LST_FOREACH.  If gn->unmade is
 *	nonzero and that is meant to imply a cycle in the graph, then
 *	cycle is TRUE.
 *
 * Side Effects:
 *	A message may be printed.
 */
static void
MakePrintStatus(GNode *gn, Boolean cycle)
{
	LstNode	*ln;

	if (gn->made == UPTODATE) {
		printf("`%s' is up to date.\n", gn->name);

	} else if (gn->unmade != 0) {
		if (cycle) {
			/*
			 * If printing cycles and came to one that has unmade
			 * children, print out the cycle by recursing on its
			 * children. Note a cycle like:
			 *	a : b
			 *	b : c
			 *	c : b
			 * will cause this to erroneously complain about a
			 * being in the cycle, but this is a good approximation.
			 */
			if (gn->made == CYCLE) {
				Error("Graph cycles through `%s'", gn->name);
				gn->made = ENDCYCLE;
				LST_FOREACH(ln, &gn->children)
					MakePrintStatus(Lst_Datum(ln), TRUE);
				gn->made = UNMADE;
			} else if (gn->made != ENDCYCLE) {
				gn->made = CYCLE;
				LST_FOREACH(ln, &gn->children)
					MakePrintStatus(Lst_Datum(ln), TRUE);
			}
		} else {
			printf("`%s' not remade because of errors.\n",
			    gn->name);
		}
	}
}

/**
 * Make_Run
 *	Initialize the nodes to remake and the list of nodes which are
 *	ready to be made by doing a breadth-first traversal of the graph
 *	starting from the nodes in the given list. Once this traversal
 *	is finished, all the 'leaves' of the graph are in the toBeMade
 *	queue.
 *	Using this queue and the Job module, work back up the graph,
 *	calling on MakeStartJobs to keep the job table as full as
 *	possible.
 *
 * Results:
 *	TRUE if work was done. FALSE otherwise.
 *
 * Side Effects:
 *	The make field of all nodes involved in the creation of the given
 *	targets is set to 1. The toBeMade list is set to contain all the
 *	'leaves' of these subgraphs.
 */
Boolean
Make_Run(Lst *targs)
{
	GNode	*gn;		/* a temporary pointer */
	GNode	*cgn;
	Lst	examine;	/* List of targets to examine */
	LstNode	*ln;

	Lst_Init(&examine);
	Lst_Duplicate(&examine, targs, NOCOPY);
	numNodes = 0;

	/*
	 * Make an initial downward pass over the graph, marking nodes to be
	 * made as we go down. We call Suff_FindDeps to find where a node is and
	 * to get some children for it if it has none and also has no commands.
	 * If the node is a leaf, we stick it on the toBeMade queue to
	 * be looked at in a minute, otherwise we add its children to our queue
	 * and go on about our business.
	 */
	while (!Lst_IsEmpty(&examine)) {
		gn = Lst_DeQueue(&examine);

		if (!gn->make) {
			gn->make = TRUE;
			numNodes++;

			/*
			 * Apply any .USE rules before looking for implicit
			 * dependencies to make sure everything has commands
			 * that should...
			 */
			LST_FOREACH(ln, &gn->children)
				if (Make_HandleUse(Lst_Datum(ln), gn))
					break;

			Suff_FindDeps(gn);

			if (gn->unmade != 0) {
				LST_FOREACH(ln, &gn->children) {
					cgn = Lst_Datum(ln);
					if (!cgn->make && !(cgn->type & OP_USE))
						Lst_EnQueue(&examine, cgn);
				}
			} else {
				Lst_EnQueue(&toBeMade, gn);
			}
		}
	}

	if (queryFlag) {
		/*
		 * We wouldn't do any work unless we could start some jobs in
		 * the next loop... (we won't actually start any, of course,
		 * this is just to see if any of the targets was out of date)
		 */
		return (MakeStartJobs());

	} else {
		/*
		 * Initialization. At the moment, no jobs are running and
		 * until some get started, nothing will happen since the
		 * remaining upward traversal of the graph is performed by the
		 * routines in job.c upon the finishing of a job. So we fill
		 * the Job table as much as we can before going into our loop.
		 */
		MakeStartJobs();
	}

	/*
	 * Main Loop: The idea here is that the ending of jobs will take
	 * care of the maintenance of data structures and the waiting for output
	 * will cause us to be idle most of the time while our children run as
	 * much as possible. Because the job table is kept as full as possible,
	 * the only time when it will be empty is when all the jobs which need
	 * running have been run, so that is the end condition of this loop.
	 * Note that the Job module will exit if there were any errors unless
	 * the keepgoing flag was given.
	 */
	while (!Job_Empty()) {
		Job_CatchOutput(!Lst_IsEmpty(&toBeMade));
		Job_CatchChildren(!usePipes);
		MakeStartJobs();
	}

	Job_Finish();

	/*
	 * Print the final status of each target. E.g. if it wasn't made
	 * because some inferior reported an error.
	 */
	LST_FOREACH(ln, targs)
		MakePrintStatus(Lst_Datum(ln), (makeErrors == 0) && (numNodes != 0));

	return (TRUE);
}