source: kBuild/trunk/src/kmk/dir.c@ 30

/*
 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
 * Copyright (c) 1988, 1989 by Adam de Boor
 * 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.
 */

#ifndef lint
#if 0
static char sccsid[] = "@(#)dir.c       8.2 (Berkeley) 1/2/94";
#else
static const char rcsid[] =
  "$FreeBSD: src/usr.bin/make/dir.c,v 1.10.2.1 2001/02/13 03:13:57 will Exp $";
#endif
#endif /* not lint */

/*-
 * dir.c --
 *      Directory searching using wildcards and/or normal names...
 *      Used both for source wildcarding in the Makefile and for finding
 *      implicit sources.
 *
 * The interface for this module is:
 *      Dir_Init            Initialize the module.
 *
 *      Dir_End             Cleanup the module.
 *
 *      Dir_HasWildcards    Returns TRUE if the name given it needs to
 *                          be wildcard-expanded.
 *
 *      Dir_Expand          Given a pattern and a path, return a Lst of names
 *                          which match the pattern on the search path.
 *
 *      Dir_FindFile        Searches for a file on a given search path.
 *                          If it exists, the entire path is returned.
 *                          Otherwise NULL is returned.
 *
 *      Dir_MTime           Return the modification time of a node. The file
 *                          is searched for along the default search path.
 *                          The path and mtime fields of the node are filled
 *                          in.
 *
 *      Dir_AddDir          Add a directory to a search path.
 *
 *      Dir_MakeFlags       Given a search path and a command flag, create
 *                          a string with each of the directories in the path
 *                          preceded by the command flag and all of them
 *                          separated by a space.
 *
 *      Dir_Destroy         Destroy an element of a search path. Frees up all
 *                          things that can be freed for the element as long
 *                          as the element is no longer referenced by any other
 *                          search path.
 *      Dir_ClearPath       Resets a search path to the empty list.
 *
 * For debugging:
 *      Dir_PrintDirectories    Print stats about the directory cache.
 */

#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include "make.h"
#include "hash.h"
#include "dir.h"

/*
 *      A search path consists of a Lst of Path structures. A Path structure
 *      has in it the name of the directory and a hash table of all the files
 *      in the directory. This is used to cut down on the number of system
 *      calls necessary to find implicit dependents and their like. Since
 *      these searches are made before any actions are taken, we need not
 *      worry about the directory changing due to creation commands. If this
 *      hampers the style of some makefiles, they must be changed.
 *
 *      A list of all previously-read directories is kept in the
 *      openDirectories Lst. This list is checked first before a directory
 *      is opened.
 *
 *      The need for the caching of whole directories is brought about by
 *      the multi-level transformation code in suff.c, which tends to search
 *      for far more files than regular make does. In the initial
 *      implementation, the amount of time spent performing "stat" calls was
 *      truly astronomical. The problem with hashing at the start is,
 *      of course, that pmake doesn't then detect changes to these directories
 *      during the course of the make. Three possibilities suggest themselves:
 *
 *          1) just use stat to test for a file's existence. As mentioned
 *             above, this is very inefficient due to the number of checks
 *             engendered by the multi-level transformation code.
 *          2) use readdir() and company to search the directories, keeping
 *             them open between checks. I have tried this and while it
 *             didn't slow down the process too much, it could severely
 *             affect the amount of parallelism available as each directory
 *             open would take another file descriptor out of play for
 *             handling I/O for another job. Given that it is only recently
 *             that UNIX OS's have taken to allowing more than 20 or 32
 *             file descriptors for a process, this doesn't seem acceptable
 *             to me.
 *          3) record the mtime of the directory in the Path structure and
 *             verify the directory hasn't changed since the contents were
 *             hashed. This will catch the creation or deletion of files,
 *             but not the updating of files. However, since it is the
 *             creation and deletion that is the problem, this could be
 *             a good thing to do. Unfortunately, if the directory (say ".")
 *             were fairly large and changed fairly frequently, the constant
 *             rehashing could seriously degrade performance. It might be
 *             good in such cases to keep track of the number of rehashes
 *             and if the number goes over a (small) limit, resort to using
 *             stat in its place.
 *
 *      An additional thing to consider is that pmake is used primarily
 *      to create C programs and until recently pcc-based compilers refused
 *      to allow you to specify where the resulting object file should be
 *      placed. This forced all objects to be created in the current
 *      directory. This isn't meant as a full excuse, just an explanation of
 *      some of the reasons for the caching used here.
 *
 *      One more note: the location of a target's file is only performed
 *      on the downward traversal of the graph and then only for terminal
 *      nodes in the graph. This could be construed as wrong in some cases,
 *      but prevents inadvertent modification of files when the "installed"
 *      directory for a file is provided in the search path.
 *
 *      Another data structure maintained by this module is an mtime
 *      cache used when the searching of cached directories fails to find
 *      a file. In the past, Dir_FindFile would simply perform an access()
 *      call in such a case to determine if the file could be found using
 *      just the name given. When this hit, however, all that was gained
 *      was the knowledge that the file existed. Given that an access() is
 *      essentially a stat() without the copyout() call, and that the same
 *      filesystem overhead would have to be incurred in Dir_MTime, it made
 *      sense to replace the access() with a stat() and record the mtime
 *      in a cache for when Dir_MTime was actually called.
 */

Lst          dirSearchPath;     /* main search path */

static Lst   openDirectories;   /* the list of all open directories */

/*
 * Variables for gathering statistics on the efficiency of the hashing
 * mechanism.
 */
static int    hits,           /* Found in directory cache */
              misses,         /* Sad, but not evil misses */
              nearmisses,     /* Found under search path */
              bigmisses;      /* Sought by itself */

static Path       *dot;     /* contents of current directory */
static Hash_Table mtimes;   /* Results of doing a last-resort stat in
                             * Dir_FindFile -- if we have to go to the
                             * system to find the file, we might as well
                             * have its mtime on record. XXX: If this is done
                             * way early, there's a chance other rules will
                             * have already updated the file, in which case
                             * we'll update it again. Generally, there won't
                             * be two rules to update a single file, so this
                             * should be ok, but... */


static int DirFindName __P((ClientData, ClientData));
static int DirMatchFiles __P((char *, Path *, Lst));
static void DirExpandCurly __P((char *, char *, Lst, Lst));
static void DirExpandInt __P((char *, Lst, Lst));
static int DirPrintWord __P((ClientData, ClientData));
static int DirPrintDir __P((ClientData, ClientData));

/*-
 *-----------------------------------------------------------------------
 * Dir_Init --
 *      initialize things for this module
 *
 * Results:
 *      none
 *
 * Side Effects:
 *      some directories may be opened.
 *-----------------------------------------------------------------------
 */
void
Dir_Init ()
{
    dirSearchPath = Lst_Init (FALSE);
    openDirectories = Lst_Init (FALSE);
    Hash_InitTable(&mtimes, 0);

    /*
     * Since the Path structure is placed on both openDirectories and
     * the path we give Dir_AddDir (which in this case is openDirectories),
     * we need to remove "." from openDirectories and what better time to
     * do it than when we have to fetch the thing anyway?
     */
    Dir_AddDir (openDirectories, ".");
    dot = (Path *) Lst_DeQueue (openDirectories);
    if (dot == (Path *) NULL)
        err(1, "cannot open current directory");

    /*
     * We always need to have dot around, so we increment its reference count
     * to make sure it's not destroyed.
     */
    dot->refCount += 1;
}

/*-
 *-----------------------------------------------------------------------
 * Dir_End --
 *      cleanup things for this module
 *
 * Results:
 *      none
 *
 * Side Effects:
 *      none
 *-----------------------------------------------------------------------
 */
void
Dir_End()
{
    dot->refCount -= 1;
    Dir_Destroy((ClientData) dot);
    Dir_ClearPath(dirSearchPath);
    Lst_Destroy(dirSearchPath, NOFREE);
    Dir_ClearPath(openDirectories);
    Lst_Destroy(openDirectories, NOFREE);
    Hash_DeleteTable(&mtimes);
}

/*-
 *-----------------------------------------------------------------------
 * DirFindName --
 *      See if the Path structure describes the same directory as the
 *      given one by comparing their names. Called from Dir_AddDir via
 *      Lst_Find when searching the list of open directories.
 *
 * Results:
 *      0 if it is the same. Non-zero otherwise
 *
 * Side Effects:
 *      None
 *-----------------------------------------------------------------------
 */
static int
DirFindName (p, dname)
    ClientData    p;          /* Current name */
    ClientData    dname;      /* Desired name */
{
    return (strcmp (((Path *)p)->name, (char *) dname));
}

/*-
 *-----------------------------------------------------------------------
 * Dir_HasWildcards  --
 *      see if the given name has any wildcard characters in it
 *
 * Results:
 *      returns TRUE if the word should be expanded, FALSE otherwise
 *
 * Side Effects:
 *      none
 *-----------------------------------------------------------------------
 */
Boolean
Dir_HasWildcards (name)
    char          *name;        /* name to check */
{
    register char *cp;

    for (cp = name; *cp; cp++) {
        switch(*cp) {
        case '{':
        case '[':
        case '?':
        case '*':
            return (TRUE);
        }
    }
    return (FALSE);
}

/*-
 *-----------------------------------------------------------------------
 * DirMatchFiles --
 *      Given a pattern and a Path structure, see if any files
 *      match the pattern and add their names to the 'expansions' list if
 *      any do. This is incomplete -- it doesn't take care of patterns like
 *      src / *src / *.c properly (just *.c on any of the directories), but it
 *      will do for now.
 *
 * Results:
 *      Always returns 0
 *
 * Side Effects:
 *      File names are added to the expansions lst. The directory will be
 *      fully hashed when this is done.
 *-----------------------------------------------------------------------
 */
static int
DirMatchFiles (pattern, p, expansions)
    char          *pattern;     /* Pattern to look for */
    Path          *p;           /* Directory to search */
    Lst           expansions;   /* Place to store the results */
{
    Hash_Search   search;       /* Index into the directory's table */
    Hash_Entry    *entry;       /* Current entry in the table */
    Boolean       isDot;        /* TRUE if the directory being searched is . */

    isDot = (*p->name == '.' && p->name[1] == '\0');

    for (entry = Hash_EnumFirst(&p->files, &search);
         entry != (Hash_Entry *)NULL;
         entry = Hash_EnumNext(&search))
    {
        /*
         * See if the file matches the given pattern. Note we follow the UNIX
         * convention that dot files will only be found if the pattern
         * begins with a dot (note also that as a side effect of the hashing
         * scheme, .* won't match . or .. since they aren't hashed).
         */
        if (Str_Match(entry->name, pattern) &&
            ((entry->name[0] != '.') ||
             (pattern[0] == '.')))
        {
            (void)Lst_AtEnd(expansions,
                            (isDot ? estrdup(entry->name) :
                             str_concat(p->name, entry->name,
                                        STR_ADDSLASH)));
        }
    }
    return (0);
}

/*-
 *-----------------------------------------------------------------------
 * DirExpandCurly --
 *      Expand curly braces like the C shell. Does this recursively.
 *      Note the special case: if after the piece of the curly brace is
 *      done there are no wildcard characters in the result, the result is
 *      placed on the list WITHOUT CHECKING FOR ITS EXISTENCE.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The given list is filled with the expansions...
 *
 *-----------------------------------------------------------------------
 */
static void
DirExpandCurly(word, brace, path, expansions)
    char          *word;        /* Entire word to expand */
    char          *brace;       /* First curly brace in it */
    Lst           path;         /* Search path to use */
    Lst           expansions;   /* Place to store the expansions */
{
    char          *end;         /* Character after the closing brace */
    char          *cp;          /* Current position in brace clause */
    char          *start;       /* Start of current piece of brace clause */
    int           bracelevel;   /* Number of braces we've seen. If we see a
                                 * right brace when this is 0, we've hit the
                                 * end of the clause. */
    char          *file;        /* Current expansion */
    int           otherLen;     /* The length of the other pieces of the
                                 * expansion (chars before and after the
                                 * clause in 'word') */
    char          *cp2;         /* Pointer for checking for wildcards in
                                 * expansion before calling Dir_Expand */

    start = brace+1;

    /*
     * Find the end of the brace clause first, being wary of nested brace
     * clauses.
     */
    for (end = start, bracelevel = 0; *end != '\0'; end++) {
        if (*end == '{') {
            bracelevel++;
        } else if ((*end == '}') && (bracelevel-- == 0)) {
            break;
        }
    }
    if (*end == '\0') {
        Error("Unterminated {} clause \"%s\"", start);
        return;
    } else {
        end++;
    }
    otherLen = brace - word + strlen(end);

    for (cp = start; cp < end; cp++) {
        /*
         * Find the end of this piece of the clause.
         */
        bracelevel = 0;
        while (*cp != ',') {
            if (*cp == '{') {
                bracelevel++;
            } else if ((*cp == '}') && (bracelevel-- <= 0)) {
                break;
            }
            cp++;
        }
        /*
         * Allocate room for the combination and install the three pieces.
         */
        file = emalloc(otherLen + cp - start + 1);
        if (brace != word) {
            strncpy(file, word, brace-word);
        }
        if (cp != start) {
            strncpy(&file[brace-word], start, cp-start);
        }
        strcpy(&file[(brace-word)+(cp-start)], end);

        /*
         * See if the result has any wildcards in it. If we find one, call
         * Dir_Expand right away, telling it to place the result on our list
         * of expansions.
         */
        for (cp2 = file; *cp2 != '\0'; cp2++) {
            switch(*cp2) {
            case '*':
            case '?':
            case '{':
            case '[':
                Dir_Expand(file, path, expansions);
                goto next;
            }
        }
        if (*cp2 == '\0') {
            /*
             * Hit the end w/o finding any wildcards, so stick the expansion
             * on the end of the list.
             */
            (void)Lst_AtEnd(expansions, file);
        } else {
        next:
            free(file);
        }
        start = cp+1;
    }
}


/*-
 *-----------------------------------------------------------------------
 * DirExpandInt --
 *      Internal expand routine. Passes through the directories in the
 *      path one by one, calling DirMatchFiles for each. NOTE: This still
 *      doesn't handle patterns in directories...
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Things are added to the expansions list.
 *
 *-----------------------------------------------------------------------
 */
static void
DirExpandInt(word, path, expansions)
    char          *word;        /* Word to expand */
    Lst           path;         /* Path on which to look */
    Lst           expansions;   /* Place to store the result */
{
    LstNode       ln;           /* Current node */
    Path          *p;           /* Directory in the node */

    if (Lst_Open(path) == SUCCESS) {
        while ((ln = Lst_Next(path)) != NILLNODE) {
            p = (Path *)Lst_Datum(ln);
            DirMatchFiles(word, p, expansions);
        }
        Lst_Close(path);
    }
}

/*-
 *-----------------------------------------------------------------------
 * DirPrintWord --
 *      Print a word in the list of expansions. Callback for Dir_Expand
 *      when DEBUG(DIR), via Lst_ForEach.
 *
 * Results:
 *      === 0
 *
 * Side Effects:
 *      The passed word is printed, followed by a space.
 *
 *-----------------------------------------------------------------------
 */
static int
DirPrintWord(word, dummy)
    ClientData  word;
    ClientData  dummy;
{
    printf("%s ", (char *) word);

    return(dummy ? 0 : 0);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_Expand  --
 *      Expand the given word into a list of words by globbing it looking
 *      in the directories on the given search path.
 *
 * Results:
 *      A list of words consisting of the files which exist along the search
 *      path matching the given pattern.
 *
 * Side Effects:
 *      Directories may be opened. Who knows?
 *-----------------------------------------------------------------------
 */
void
Dir_Expand (word, path, expansions)
    char    *word;      /* the word to expand */
    Lst     path;       /* the list of directories in which to find
                         * the resulting files */
    Lst     expansions; /* the list on which to place the results */
{
    char          *cp;

    if (DEBUG(DIR)) {
        printf("expanding \"%s\"...", word);
    }

    cp = strchr(word, '{');
    if (cp) {
        DirExpandCurly(word, cp, path, expansions);
    } else {
        cp = strchr(word, '/');
        if (cp) {
            /*
             * The thing has a directory component -- find the first wildcard
             * in the string.
             */
            for (cp = word; *cp; cp++) {
                if (*cp == '?' || *cp == '[' || *cp == '*' || *cp == '{') {
                    break;
                }
            }
            if (*cp == '{') {
                /*
                 * This one will be fun.
                 */
                DirExpandCurly(word, cp, path, expansions);
                return;
            } else if (*cp != '\0') {
                /*
                 * Back up to the start of the component
                 */
                char  *dirpath;

                while (cp > word && *cp != '/') {
                    cp--;
                }
                if (cp != word) {
                    char sc;
                    /*
                     * If the glob isn't in the first component, try and find
                     * all the components up to the one with a wildcard.
                     */
                    sc = cp[1];
                    cp[1] = '\0';
                    dirpath = Dir_FindFile(word, path);
                    cp[1] = sc;
                    /*
                     * dirpath is null if can't find the leading component
                     * XXX: Dir_FindFile won't find internal components.
                     * i.e. if the path contains ../Etc/Object and we're
                     * looking for Etc, it won't be found. Ah well.
                     * Probably not important.
                     */
                    if (dirpath != (char *)NULL) {
                        char *dp = &dirpath[strlen(dirpath) - 1];
                        if (*dp == '/')
                            *dp = '\0';
                        path = Lst_Init(FALSE);
                        Dir_AddDir(path, dirpath);
                        DirExpandInt(cp+1, path, expansions);
                        Lst_Destroy(path, NOFREE);
                    }
                } else {
                    /*
                     * Start the search from the local directory
                     */
                    DirExpandInt(word, path, expansions);
                }
            } else {
                /*
                 * Return the file -- this should never happen.
                 */
                DirExpandInt(word, path, expansions);
            }
        } else {
            /*
             * First the files in dot
             */
            DirMatchFiles(word, dot, expansions);

            /*
             * Then the files in every other directory on the path.
             */
            DirExpandInt(word, path, expansions);
        }
    }
    if (DEBUG(DIR)) {
        Lst_ForEach(expansions, DirPrintWord, (ClientData) 0);
        fputc('\n', stdout);
    }
}

/*-
 *-----------------------------------------------------------------------
 * Dir_FindFile  --
 *      Find the file with the given name along the given search path.
 *
 * Results:
 *      The path to the file or NULL. This path is guaranteed to be in a
 *      different part of memory than name and so may be safely free'd.
 *
 * Side Effects:
 *      If the file is found in a directory which is not on the path
 *      already (either 'name' is absolute or it is a relative path
 *      [ dir1/.../dirn/file ] which exists below one of the directories
 *      already on the search path), its directory is added to the end
 *      of the path on the assumption that there will be more files in
 *      that directory later on. Sometimes this is true. Sometimes not.
 *-----------------------------------------------------------------------
 */
char *
Dir_FindFile (name, path)
    char          *name;    /* the file to find */
    Lst           path;     /* the Lst of directories to search */
{
    register char *p1;      /* pointer into p->name */
    register char *p2;      /* pointer into name */
    LstNode       ln;       /* a list element */
    register char *file;    /* the current filename to check */
    register Path *p;       /* current path member */
    register char *cp;      /* index of first slash, if any */
    Boolean       hasSlash; /* true if 'name' contains a / */
    struct stat   stb;      /* Buffer for stat, if necessary */
    Hash_Entry    *entry;   /* Entry for mtimes table */

    /*
     * Find the final component of the name and note whether it has a
     * slash in it (the name, I mean)
     */
    cp = strrchr (name, '/');
    if (cp) {
        hasSlash = TRUE;
        cp += 1;
    } else {
        hasSlash = FALSE;
        cp = name;
    }

    if (DEBUG(DIR)) {
        printf("Searching for %s...", name);
    }
    /*
     * No matter what, we always look for the file in the current directory
     * before anywhere else and we *do not* add the ./ to it if it exists.
     * This is so there are no conflicts between what the user specifies
     * (fish.c) and what pmake finds (./fish.c).
     */
    if ((!hasSlash || (cp - name == 2 && *name == '.')) &&
        (Hash_FindEntry (&dot->files, cp) != (Hash_Entry *)NULL)) {
            if (DEBUG(DIR)) {
                printf("in '.'\n");
            }
            hits += 1;
            dot->hits += 1;
            return (estrdup (name));
    }

    if (Lst_Open (path) == FAILURE) {
        if (DEBUG(DIR)) {
            printf("couldn't open path, file not found\n");
        }
        misses += 1;
        return ((char *) NULL);
    }

    /*
     * We look through all the directories on the path seeking one which
     * contains the final component of the given name and whose final
     * component(s) match the name's initial component(s). If such a beast
     * is found, we concatenate the directory name and the final component
     * and return the resulting string. If we don't find any such thing,
     * we go on to phase two...
     */
    while ((ln = Lst_Next (path)) != NILLNODE) {
        p = (Path *) Lst_Datum (ln);
        if (DEBUG(DIR)) {
            printf("%s...", p->name);
        }
        if (Hash_FindEntry (&p->files, cp) != (Hash_Entry *)NULL) {
            if (DEBUG(DIR)) {
                printf("here...");
            }
            if (hasSlash) {
                /*
                 * If the name had a slash, its initial components and p's
                 * final components must match. This is false if a mismatch
                 * is encountered before all of the initial components
                 * have been checked (p2 > name at the end of the loop), or
                 * we matched only part of one of the components of p
                 * along with all the rest of them (*p1 != '/').
                 */
                p1 = p->name + strlen (p->name) - 1;
                p2 = cp - 2;
                while (p2 >= name && p1 >= p->name && *p1 == *p2) {
                    p1 -= 1; p2 -= 1;
                }
                if (p2 >= name || (p1 >= p->name && *p1 != '/')) {
                    if (DEBUG(DIR)) {
                        printf("component mismatch -- continuing...");
                    }
                    continue;
                }
            }
            file = str_concat (p->name, cp, STR_ADDSLASH);
            if (DEBUG(DIR)) {
                printf("returning %s\n", file);
            }
            Lst_Close (path);
            p->hits += 1;
            hits += 1;
            return (file);
        } else if (hasSlash) {
            /*
             * If the file has a leading path component and that component
             * exactly matches the entire name of the current search
             * directory, we assume the file doesn't exist and return NULL.
             */
            for (p1 = p->name, p2 = name; *p1 && *p1 == *p2; p1++, p2++) {
                continue;
            }
            if (*p1 == '\0' && p2 == cp - 1) {
                if (DEBUG(DIR)) {
                    printf("must be here but isn't -- returing NULL\n");
                }
                Lst_Close (path);
                return ((char *) NULL);
            }
        }
    }

    /*
     * We didn't find the file on any existing members of the directory.
     * If the name doesn't contain a slash, that means it doesn't exist.
     * If it *does* contain a slash, however, there is still hope: it
     * could be in a subdirectory of one of the members of the search
     * path. (eg. /usr/include and sys/types.h. The above search would
     * fail to turn up types.h in /usr/include, but it *is* in
     * /usr/include/sys/types.h) If we find such a beast, we assume there
     * will be more (what else can we assume?) and add all but the last
     * component of the resulting name onto the search path (at the
     * end). This phase is only performed if the file is *not* absolute.
     */
    if (!hasSlash) {
        if (DEBUG(DIR)) {
            printf("failed.\n");
        }
        misses += 1;
        return ((char *) NULL);
    }

    if (*name != '/') {
        Boolean checkedDot = FALSE;

        if (DEBUG(DIR)) {
            printf("failed. Trying subdirectories...");
        }
        (void) Lst_Open (path);
        while ((ln = Lst_Next (path)) != NILLNODE) {
            p = (Path *) Lst_Datum (ln);
            if (p != dot) {
                file = str_concat (p->name, name, STR_ADDSLASH);
            } else {
                /*
                 * Checking in dot -- DON'T put a leading ./ on the thing.
                 */
                file = estrdup(name);
                checkedDot = TRUE;
            }
            if (DEBUG(DIR)) {
                printf("checking %s...", file);
            }


            if (stat (file, &stb) == 0) {
                if (DEBUG(DIR)) {
                    printf("got it.\n");
                }

                Lst_Close (path);

                /*
                 * We've found another directory to search. We know there's
                 * a slash in 'file' because we put one there. We nuke it after
                 * finding it and call Dir_AddDir to add this new directory
                 * onto the existing search path. Once that's done, we restore
                 * the slash and triumphantly return the file name, knowing
                 * that should a file in this directory every be referenced
                 * again in such a manner, we will find it without having to do
                 * numerous numbers of access calls. Hurrah!
                 */
                cp = strrchr (file, '/');
                *cp = '\0';
                Dir_AddDir (path, file);
                *cp = '/';

                /*
                 * Save the modification time so if it's needed, we don't have
                 * to fetch it again.
                 */
                if (DEBUG(DIR)) {
                    printf("Caching %s for %s\n", Targ_FmtTime(stb.st_mtime),
                            file);
                }
                entry = Hash_CreateEntry(&mtimes, (char *) file,
                                         (Boolean *)NULL);
                Hash_SetValue(entry, (long)stb.st_mtime);
                nearmisses += 1;
                return (file);
            } else {
                free (file);
            }
        }

        if (DEBUG(DIR)) {
            printf("failed. ");
        }
        Lst_Close (path);

        if (checkedDot) {
            /*
             * Already checked by the given name, since . was in the path,
             * so no point in proceeding...
             */
            if (DEBUG(DIR)) {
                printf("Checked . already, returning NULL\n");
            }
            return(NULL);
        }
    }

    /*
     * Didn't find it that way, either. Sigh. Phase 3. Add its directory
     * onto the search path in any case, just in case, then look for the
     * thing in the hash table. If we find it, grand. We return a new
     * copy of the name. Otherwise we sadly return a NULL pointer. Sigh.
     * Note that if the directory holding the file doesn't exist, this will
     * do an extra search of the final directory on the path. Unless something
     * weird happens, this search won't succeed and life will be groovy.
     *
     * Sigh. We cannot add the directory onto the search path because
     * of this amusing case:
     * $(INSTALLDIR)/$(FILE): $(FILE)
     *
     * $(FILE) exists in $(INSTALLDIR) but not in the current one.
     * When searching for $(FILE), we will find it in $(INSTALLDIR)
     * b/c we added it here. This is not good...
     */
#ifdef notdef
    cp[-1] = '\0';
    Dir_AddDir (path, name);
    cp[-1] = '/';

    bigmisses += 1;
    ln = Lst_Last (path);
    if (ln == NILLNODE) {
        return ((char *) NULL);
    } else {
        p = (Path *) Lst_Datum (ln);
    }

    if (Hash_FindEntry (&p->files, cp) != (Hash_Entry *)NULL) {
        return (estrdup (name));
    } else {
        return ((char *) NULL);
    }
#else /* !notdef */
    if (DEBUG(DIR)) {
        printf("Looking for \"%s\"...", name);
    }

    bigmisses += 1;
    entry = Hash_FindEntry(&mtimes, name);
    if (entry != (Hash_Entry *)NULL) {
        if (DEBUG(DIR)) {
            printf("got it (in mtime cache)\n");
        }
        return(estrdup(name));
    } else if (stat (name, &stb) == 0) {
        entry = Hash_CreateEntry(&mtimes, name, (Boolean *)NULL);
        if (DEBUG(DIR)) {
            printf("Caching %s for %s\n", Targ_FmtTime(stb.st_mtime),
                    name);
        }
        Hash_SetValue(entry, (long)stb.st_mtime);
        return (estrdup (name));
    } else {
        if (DEBUG(DIR)) {
            printf("failed. Returning NULL\n");
        }
        return ((char *)NULL);
    }
#endif /* notdef */
}

/*-
 *-----------------------------------------------------------------------
 * Dir_MTime  --
 *      Find the modification time of the file described by gn along the
 *      search path dirSearchPath.
 *
 * Results:
 *      The modification time or 0 if it doesn't exist
 *
 * Side Effects:
 *      The modification time is placed in the node's mtime slot.
 *      If the node didn't have a path entry before, and Dir_FindFile
 *      found one for it, the full name is placed in the path slot.
 *-----------------------------------------------------------------------
 */
int
Dir_MTime (gn)
    GNode         *gn;        /* the file whose modification time is
                               * desired */
{
    char          *fullName;  /* the full pathname of name */
    struct stat   stb;        /* buffer for finding the mod time */
    Hash_Entry    *entry;

    if (gn->type & OP_ARCHV) {
        return Arch_MTime (gn);
    } else if (gn->path == (char *)NULL) {
        fullName = Dir_FindFile (gn->name, dirSearchPath);
    } else {
        fullName = gn->path;
    }

    if (fullName == (char *)NULL) {
        fullName = estrdup(gn->name);
    }

    entry = Hash_FindEntry(&mtimes, fullName);
    if (entry != (Hash_Entry *)NULL) {
        /*
         * Only do this once -- the second time folks are checking to
         * see if the file was actually updated, so we need to actually go
         * to the file system.
         */
        if (DEBUG(DIR)) {
            printf("Using cached time %s for %s\n",
                    Targ_FmtTime((time_t)(long)Hash_GetValue(entry)), fullName);
        }
        stb.st_mtime = (time_t)(long)Hash_GetValue(entry);
        Hash_DeleteEntry(&mtimes, entry);
    } else if (stat (fullName, &stb) < 0) {
        if (gn->type & OP_MEMBER) {
            if (fullName != gn->path)
                free(fullName);
            return Arch_MemMTime (gn);
        } else {
            stb.st_mtime = 0;
        }
    }
    if (fullName && gn->path == (char *)NULL) {
        gn->path = fullName;
    }

    gn->mtime = stb.st_mtime;
    return (gn->mtime);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_AddDir --
 *      Add the given name to the end of the given path. The order of
 *      the arguments is backwards so ParseDoDependency can do a
 *      Lst_ForEach of its list of paths...
 *
 * Results:
 *      none
 *
 * Side Effects:
 *      A structure is added to the list and the directory is
 *      read and hashed.
 *-----------------------------------------------------------------------
 */
void
Dir_AddDir (path, name)
    Lst           path;       /* the path to which the directory should be
                               * added */
    char          *name;      /* the name of the directory to add */
{
    LstNode       ln;         /* node in case Path structure is found */
    register Path *p;         /* pointer to new Path structure */
    DIR           *d;         /* for reading directory */
    register struct dirent *dp; /* entry in directory */

    ln = Lst_Find (openDirectories, (ClientData)name, DirFindName);
    if (ln != NILLNODE) {
        p = (Path *)Lst_Datum (ln);
        if (Lst_Member(path, (ClientData)p) == NILLNODE) {
            p->refCount += 1;
            (void)Lst_AtEnd (path, (ClientData)p);
        }
    } else {
        if (DEBUG(DIR)) {
            printf("Caching %s...", name);
            fflush(stdout);
        }

        if ((d = opendir (name)) != (DIR *) NULL) {
            p = (Path *) emalloc (sizeof (Path));
            p->name = estrdup (name);
            p->hits = 0;
            p->refCount = 1;
            Hash_InitTable (&p->files, -1);

            while ((dp = readdir (d)) != (struct dirent *) NULL) {
#if defined(sun) && defined(d_ino) /* d_ino is a sunos4 #define for d_fileno */
                /*
                 * The sun directory library doesn't check for a 0 inode
                 * (0-inode slots just take up space), so we have to do
                 * it ourselves.
                 */
                if (dp->d_fileno == 0) {
                    continue;
                }
#endif /* sun && d_ino */

                /* Skip the '.' and '..' entries by checking for them
                 * specifically instead of assuming readdir() reuturns them in
                 * that order when first going through a directory.  This is
                 * needed for XFS over NFS filesystems since SGI does not
                 * guarantee that these are * the first two entries returned
                 * from readdir().
                 */
                if (ISDOT(dp->d_name) || ISDOTDOT(dp->d_name))
                        continue;

                (void)Hash_CreateEntry(&p->files, dp->d_name, (Boolean *)NULL);
            }
            (void) closedir (d);
            (void)Lst_AtEnd (openDirectories, (ClientData)p);
            (void)Lst_AtEnd (path, (ClientData)p);
        }
        if (DEBUG(DIR)) {
            printf("done\n");
        }
    }
}

/*-
 *-----------------------------------------------------------------------
 * Dir_CopyDir --
 *      Callback function for duplicating a search path via Lst_Duplicate.
 *      Ups the reference count for the directory.
 *
 * Results:
 *      Returns the Path it was given.
 *
 * Side Effects:
 *      The refCount of the path is incremented.
 *
 *-----------------------------------------------------------------------
 */
ClientData
Dir_CopyDir(p)
    ClientData p;
{
    ((Path *) p)->refCount += 1;

    return ((ClientData)p);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_MakeFlags --
 *      Make a string by taking all the directories in the given search
 *      path and preceding them by the given flag. Used by the suffix
 *      module to create variables for compilers based on suffix search
 *      paths.
 *
 * Results:
 *      The string mentioned above. Note that there is no space between
 *      the given flag and each directory. The empty string is returned if
 *      Things don't go well.
 *
 * Side Effects:
 *      None
 *-----------------------------------------------------------------------
 */
char *
Dir_MakeFlags (flag, path)
    char          *flag;  /* flag which should precede each directory */
    Lst           path;   /* list of directories */
{
    char          *str;   /* the string which will be returned */
    char          *tstr;  /* the current directory preceded by 'flag' */
    LstNode       ln;     /* the node of the current directory */
    Path          *p;     /* the structure describing the current directory */

    str = estrdup ("");

    if (Lst_Open (path) == SUCCESS) {
        while ((ln = Lst_Next (path)) != NILLNODE) {
            p = (Path *) Lst_Datum (ln);
            tstr = str_concat (flag, p->name, 0);
            str = str_concat (str, tstr, STR_ADDSPACE | STR_DOFREE);
        }
        Lst_Close (path);
    }

    return (str);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_Destroy --
 *      Nuke a directory descriptor, if possible. Callback procedure
 *      for the suffixes module when destroying a search path.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      If no other path references this directory (refCount == 0),
 *      the Path and all its data are freed.
 *
 *-----------------------------------------------------------------------
 */
void
Dir_Destroy (pp)
    ClientData    pp;       /* The directory descriptor to nuke */
{
    Path          *p = (Path *) pp;
    p->refCount -= 1;

    if (p->refCount == 0) {
        LstNode ln;

        ln = Lst_Member (openDirectories, (ClientData)p);
        (void) Lst_Remove (openDirectories, ln);

        Hash_DeleteTable (&p->files);
        free((Address)p->name);
        free((Address)p);
    }
}

/*-
 *-----------------------------------------------------------------------
 * Dir_ClearPath --
 *      Clear out all elements of the given search path. This is different
 *      from destroying the list, notice.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The path is set to the empty list.
 *
 *-----------------------------------------------------------------------
 */
void
Dir_ClearPath(path)
    Lst     path;       /* Path to clear */
{
    Path    *p;
    while (!Lst_IsEmpty(path)) {
        p = (Path *)Lst_DeQueue(path);
        Dir_Destroy((ClientData) p);
    }
}


/*-
 *-----------------------------------------------------------------------
 * Dir_Concat --
 *      Concatenate two paths, adding the second to the end of the first.
 *      Makes sure to avoid duplicates.
 *
 * Results:
 *      None
 *
 * Side Effects:
 *      Reference counts for added dirs are upped.
 *
 *-----------------------------------------------------------------------
 */
void
Dir_Concat(path1, path2)
    Lst     path1;      /* Dest */
    Lst     path2;      /* Source */
{
    LstNode ln;
    Path    *p;

    for (ln = Lst_First(path2); ln != NILLNODE; ln = Lst_Succ(ln)) {
        p = (Path *)Lst_Datum(ln);
        if (Lst_Member(path1, (ClientData)p) == NILLNODE) {
            p->refCount += 1;
            (void)Lst_AtEnd(path1, (ClientData)p);
        }
    }
}

/********** DEBUG INFO **********/
void
Dir_PrintDirectories()
{
    LstNode     ln;
    Path        *p;

    printf ("#*** Directory Cache:\n");
    printf ("# Stats: %d hits %d misses %d near misses %d losers (%d%%)\n",
              hits, misses, nearmisses, bigmisses,
              (hits+bigmisses+nearmisses ?
               hits * 100 / (hits + bigmisses + nearmisses) : 0));
    printf ("# %-20s referenced\thits\n", "directory");
    if (Lst_Open (openDirectories) == SUCCESS) {
        while ((ln = Lst_Next (openDirectories)) != NILLNODE) {
            p = (Path *) Lst_Datum (ln);
            printf ("# %-20s %10d\t%4d\n", p->name, p->refCount, p->hits);
        }
        Lst_Close (openDirectories);
    }
}

static int DirPrintDir (p, dummy)
    ClientData  p;
    ClientData  dummy;
{
    printf ("%s ", ((Path *) p)->name);
    return (dummy ? 0 : 0);
}

void
Dir_PrintPath (path)
    Lst path;
{
    Lst_ForEach (path, DirPrintDir, (ClientData)0);
}