path: root/remake.c

/* Basic dependency engine for GNU Make.
Copyright (C) 1988, 89, 90, 91, 92, 93, 94 Free Software Foundation, Inc.
This file is part of GNU Make.

GNU Make 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 2, or (at your option)
any later version.

GNU Make 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 GNU Make; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "make.h"
#include "commands.h"
#include "job.h"
#include "dep.h"
#include "file.h"

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#else
#include <sys/file.h>
#endif

extern int try_implicit_rule ();


/* Incremented when a command is started (under -n, when one would be).  */
unsigned int commands_started = 0;

static int update_file (), update_file_1 (), check_dep (), touch_file ();
static void remake_file ();
static time_t name_mtime ();
static int library_search ();
extern time_t f_mtime ();

/* Remake all the goals in the `struct dep' chain GOALS.  Return -1 if nothing
   was done, 0 if all goals were updated successfully, or 1 if a goal failed.
   If MAKEFILES is nonzero, these goals are makefiles, so -t, -q, and -n should
   be disabled for them unless they were also command-line targets, and we
   should only make one goal at a time and return as soon as one goal whose
   `changed' member is nonzero is successfully made.  */

int
update_goal_chain (goals, makefiles)
     register struct dep *goals;
     int makefiles;
{
  int t = touch_flag, q = question_flag, n = just_print_flag;
  unsigned int j = job_slots;
  int status = -1;

#define	MTIME(file) (makefiles ? file_mtime_no_search (file) \
		     : file_mtime (file))

  /* Duplicate the chain so we can remove things from it.  */

  goals = copy_dep_chain (goals);

  {
    /* Clear the `changed' flag of each goal in the chain.
       We will use the flag below to notice when any commands
       have actually been run for a target.  When no commands
       have been run, we give an "up to date" diagnostic.  */

    struct dep *g;
    for (g = goals; g != 0; g = g->next)
      g->changed = 0;
  }

  if (makefiles)
    /* Only run one job at a time.  */
    job_slots = 1;

  /* Update all the goals until they are all finished.  */

  while (goals != 0)
    {
      register struct dep *g, *lastgoal;

      /* Start jobs that are waiting for the load to go down.  */

      start_waiting_jobs ();

      /* Wait for a child to die.  */

      reap_children (1, 0);

      lastgoal = 0;
      g = goals;
      while (g != 0)
	{
	  /* Iterate over all double-colon entries for this file.  */
	  struct file *file = g->file;
	  int stop, any_not_updated = 0;
	  for (file = g->file->double_colon ? g->file->double_colon : g->file;
	       file != NULL;
	       file = file->prev)
	    {
	      unsigned int ocommands_started;
	      int x;
	      time_t mtime = MTIME (file);
	      check_renamed (file);

	      if (makefiles)
		{
		  if (file->cmd_target)
		    {
		      touch_flag = t;
		      question_flag = q;
		      just_print_flag = n;
		    }
		  else
		    touch_flag = question_flag = just_print_flag = 0;
		}

	      /* Save the old value of `commands_started' so we can compare
		 later.  It will be incremented when any commands are
		 actually run.  */
	      ocommands_started = commands_started;

	      x = update_file (file, makefiles ? 1 : 0);
	      check_renamed (file);

	      /* Set the goal's `changed' flag if any commands were started
		 by calling update_file above.  We check this flag below to
		 decide when to give an "up to date" diagnostic.  */
	      g->changed += commands_started - ocommands_started;
	    
	      stop = 0;
	      if (x != 0 || file->updated)
		{
		  /* If STATUS was not already 1, set it to 1 if
		     updating failed, or to 0 if updating succeeded.
		     Leave STATUS as it is if no updating was done.  */

		  if (status < 1)
		    {
		      if (file->update_status != 0)
			{
			  /* Updating failed.  */
			  status = 1;
			  stop = !keep_going_flag && !makefiles;
			}
		      else if (MTIME (file) != mtime)
			{
			  /* Updating was done.  If this is a makefile and
			     just_print_flag or question_flag is set
			     (meaning -n or -q was given and this file was
			     specified as a command-line target), don't
			     change STATUS.  If STATUS is changed, we will
			     get re-exec'd, and fall into an infinite loop.  */
			  if (!makefiles
			      || (!just_print_flag && !question_flag))
			    status = 0;
			  if (makefiles && file->dontcare)
			    /* This is a default makefile.  Stop remaking.  */
			    stop = 1;
			}
		    }
		}

	      /* Keep track if any double-colon entry is not finished.
                 When they are all finished, the goal is finished.  */
	      any_not_updated |= !file->updated;

	      if (stop)
		break;
	    }

	  if (stop || !any_not_updated)
	    {
	      /* If we have found nothing whatever to do for the goal,
		 print a message saying nothing needs doing.  */

	      if (!makefiles
		  /* If the update_status is zero, we updated successfully
		     or not at all.  G->changed will have been set above if
		     any commands were actually started for this goal.  */
		  && file->update_status == 0 && !g->changed
		  /* Never give a message under -s or -q.  */
		  && !silent_flag && !question_flag)
		{
		  if (file->phony || file->cmds == 0)
		    message ("Nothing to be done for `%s'.",
			     file->name);
		  else
		    message ("`%s' is up to date.", file->name);
		  fflush (stdout);
		}

	      /* This goal is finished.  Remove it from the chain.  */
	      if (lastgoal == 0)
		goals = g->next;
	      else
		lastgoal->next = g->next;

	      /* Free the storage.  */
	      free ((char *) g);

	      g = lastgoal == 0 ? goals : lastgoal->next;

	      if (stop)
		break;
	    }
	  else
	    {
	      lastgoal = g;
	      g = g->next;
	    }
	}
    }

  if (makefiles)
    {
      touch_flag = t;
      question_flag = q;
      just_print_flag = n;
      job_slots = j;
    }

  return status;
}

/* If FILE is not up to date, execute the commands for it.
   Return 0 if successful, 1 if unsuccessful;
   but with some flag settings, just call `exit' if unsuccessful.

   DEPTH is the depth in recursions of this function.
   We increment it during the consideration of our dependencies,
   then decrement it again after finding out whether this file
   is out of date.

   If there are multiple double-colon entries for FILE,
   each is considered in turn.  */

static int
update_file (file, depth)
     struct file *file;
     unsigned int depth;
{
  register int status = 0;
  register struct file *f;

  for (f = file->double_colon ? file->double_colon : file; f != 0; f = f->prev)
    {
      status |= update_file_1 (f, depth);
      check_renamed (f);

      if (status != 0 && !keep_going_flag)
	return status;

      switch (f->command_state)
	{
	case cs_finished:
	  /* The file is done being remade.  */
	  break;

	case cs_running:
	case cs_deps_running:
	  /* Don't run the other :: rules for this
	     file until this rule is finished.  */
	  return 0;

	default:
	  error ("internal error: `%s' command_state == %d in update_file",
		 f->name, (int) f->command_state);
	  abort ();
	  break;
	}
    }

  return status;
}

/* Consider a single `struct file' and update it as appropriate.  */

static int
update_file_1 (file, depth)
     struct file *file;
     unsigned int depth;
{
  register time_t this_mtime;
  int noexist, must_make, deps_changed;
  int dep_status = 0;
  register struct dep *d, *lastd;
  int running = 0;

  DEBUGPR ("Considering target file `%s'.\n");

  if (file->updated)
    {
      if (file->update_status > 0)
	{
	  DEBUGPR ("Recently tried and failed to update file `%s'.\n");
	  return file->update_status;
	}

      DEBUGPR ("File `%s' was considered already.\n");
      return 0;
    }

  switch (file->command_state)
    {
    case cs_not_started:
    case cs_deps_running:
      break;
    case cs_running:
      DEBUGPR ("Still updating file `%s'.\n");
      return 0;
    case cs_finished:
      DEBUGPR ("Finished updating file `%s'.\n");
      return file->update_status;
    default:
      abort ();
    }

  ++depth;

  /* Notice recursive update of the same file.  */
  file->updating = 1;

  /* Looking at the file's modtime beforehand allows the possibility
     that its name may be changed by a VPATH search, and thus it may
     not need an implicit rule.  If this were not done, the file
     might get implicit commands that apply to its initial name, only
     to have that name replaced with another found by VPATH search.  */

  this_mtime = file_mtime (file);
  check_renamed (file);
  noexist = this_mtime == (time_t) -1;
  if (noexist)
    DEBUGPR ("File `%s' does not exist.\n");

  must_make = noexist;

  /* If file was specified as a target with no commands,
     come up with some default commands.  */

  if (!file->phony && file->cmds == 0 && !file->tried_implicit)
    {
      if (try_implicit_rule (file, depth))
	DEBUGPR ("Found an implicit rule for `%s'.\n");
      else
	DEBUGPR ("No implicit rule found for `%s'.\n");
      file->tried_implicit = 1;
    }
  if (file->cmds == 0 && !file->is_target
      && default_file != 0 && default_file->cmds != 0)
    {
      DEBUGPR ("Using default commands for `%s'.\n");
      file->cmds = default_file->cmds;
    }

  /* Update all non-intermediate files we depend on, if necessary,
     and see whether any of them is more recent than this file.  */

  lastd = 0;
  d = file->deps;
  while (d != 0)
    {
      time_t mtime;

      check_renamed (d->file);

      mtime = file_mtime (d->file);
      check_renamed (d->file);

      if (d->file->updating)
	{
	  error ("Circular %s <- %s dependency dropped.",
		 file->name, d->file->name);
	  if (lastd == 0)
	    {
	      file->deps = d->next;
	      free ((char *) d);
	      d = file->deps;
	    }
	  else
	    {
	      lastd->next = d->next;
	      free ((char *) d);
	      d = lastd->next;
	    }
	  continue;
	}

      d->file->parent = file;
      dep_status |= check_dep (d->file, depth, this_mtime, &must_make);
      check_renamed (d->file);

      {
	register struct file *f = d->file;
	if (f->double_colon)
	  f = f->double_colon;
	do
	  {
	    running |= (f->command_state == cs_running
			|| f->command_state == cs_deps_running);
	    f = f->prev;
	  }
	while (f != 0);
      }

      if (dep_status != 0 && !keep_going_flag)
	break;

      if (!running)
	d->changed = file_mtime (d->file) != mtime;

      lastd = d;
      d = d->next;
    }

  /* Now we know whether this target needs updating.
     If it does, update all the intermediate files we depend on.  */

  if (must_make)
    {
      for (d = file->deps; d != 0; d = d->next)
	if (d->file->intermediate)
	  {
	    time_t mtime = file_mtime (d->file);
	    check_renamed (d->file);
	    d->file->parent = file;
	    dep_status |= update_file (d->file, depth);
	    check_renamed (d->file);

	    {
	      register struct file *f = d->file;
	      if (f->double_colon)
		f = f->double_colon;
	      do
		{
		  running |= (f->command_state == cs_running
			      || f->command_state == cs_deps_running);
		  f = f->prev;
		}
	      while (f != 0);
	    }

	    if (dep_status != 0 && !keep_going_flag)
	      break;

	    if (!running)
	      d->changed = ((file->phony && file->cmds != 0)
			    || file_mtime (d->file) != mtime);
	  }
    }

  file->updating = 0;

  DEBUGPR ("Finished dependencies of target file `%s'.\n");

  if (running)
    {
      file->command_state = cs_deps_running;
      --depth;
      DEBUGPR ("The dependencies of `%s' are being made.\n");
      return 0;
    }

  /* If any dependency failed, give up now.  */

  if (dep_status != 0)
    {
      file->command_state = cs_finished;
      file->update_status = dep_status;
      file->updated = 1;

      depth--;

      DEBUGPR ("Giving up on target file `%s'.\n");

      if (depth == 0 && keep_going_flag
	  && !just_print_flag && !question_flag)
	error ("Target `%s' not remade because of errors.", file->name);

      return dep_status;
    }

  file->command_state = cs_not_started;

  /* Now record which dependencies are more
     recent than this file, so we can define $?.  */

  deps_changed = 0;
  for (d = file->deps; d != 0; d = d->next)
    {
      time_t d_mtime = file_mtime (d->file);
      check_renamed (d->file);

#if 1	/* %%% In version 4, remove this code completely to
	   implement not remaking deps if their deps are newer
	   than their parents.  */
      if (d_mtime == (time_t) -1 && !d->file->intermediate)
	/* We must remake if this dep does not
	   exist and is not intermediate.  */
	must_make = 1;
#endif

      /* Set DEPS_CHANGED if this dep actually changed.  */
      deps_changed |= d->changed;

      /* Set D->changed if either this dep actually changed,
	 or its dependent, FILE, is older or does not exist.  */
      d->changed |= noexist || d_mtime > this_mtime;

      if (debug_flag && !noexist)
	{
	  print_spaces (depth);
	  if (d_mtime == (time_t) -1)
	    printf ("Dependency `%s' does not exist.\n", dep_name (d));
	  else
	    printf ("Dependency `%s' is %s than dependent `%s'.\n",
		    dep_name (d), d->changed ? "newer" : "older", file->name);
	  fflush (stdout);
	}
    }

  /* Here depth returns to the value it had when we were called.  */
  depth--;

  if (file->double_colon && file->deps == 0)
    {
      must_make = 1;
      DEBUGPR ("Target `%s' is double-colon and has no dependencies.\n");
    }
  else if (!noexist && file->is_target && !deps_changed && file->cmds == 0)
    {
      must_make = 0;
      DEBUGPR ("No commands for `%s' and no dependencies actually changed.\n");
    }

  if (!must_make)
    {
      DEBUGPR ("No need to remake target `%s'.\n");
      file->command_state = cs_finished;
      file->update_status = 0;
      file->updated = 1;
      return 0;
    }

  DEBUGPR ("Must remake target `%s'.\n");

  /* Now, take appropriate actions to remake the file.  */
  remake_file (file);

  if (file->command_state != cs_finished)
    {
      DEBUGPR ("Commands of `%s' are being run.\n");
      return 0;
    }

  switch (file->update_status)
    {
    case 1:
      DEBUGPR ("Failed to remake target file `%s'.\n");
      break;
    case 0:
      DEBUGPR ("Successfully remade target file `%s'.\n");
      break;
    case -1:
      error ("internal error: `%s' update_status is -1 at cs_finished!",
	     file->name);
      abort ();
    default:
      error ("internal error: `%s' update_status invalid!", file->name);
      abort ();
    }

  file->updated = 1;
  return file->update_status;
}

/* Set FILE's `updated' flag and re-check its mtime and the mtime's of all
   files listed in its `also_make' member.  Under -t, this function also
   touches FILE.  */

void
notice_finished_file (file)
     register struct file *file;
{
  struct dep *d;

  file->command_state = cs_finished;
  file->updated = 1;

  if (touch_flag
      /* The update status will be:
	 	-1	if no commands were run;
		0	if some commands (+ or ${MAKE}) were run and won;
		1	if some commands were run and lost.
	 The only time we don't want to touch the target is if
	 it had some recursive commands, and they lost.  */
      && file->update_status != 1)
    {
      if (file->cmds != 0 && file->cmds->any_recurse)
	{
	  /* If all the command lines were recursive,
	     we don't want to do the touching.  */
	  unsigned int i;
	  for (i = 0; i < file->cmds->ncommand_lines; ++i)
	    if (!(file->cmds->lines_flags[i] & COMMANDS_RECURSE))
	      goto have_nonrecursing;
	}
      else
	{
	have_nonrecursing:
	  if (file->phony)
	    file->update_status = 0;
	  else
	    /* Should set file's modification date and do nothing else.  */
	    file->update_status = touch_file (file);
	}
    }

  if (!file->phony)
    {
      struct file *f;

      if (just_print_flag || question_flag
	  || (file->is_target && file->cmds == 0))
	file->last_mtime = NEW_MTIME;
      else
	file->last_mtime = 0;

      /* Propagate the change of modification time to all the double-colon
	 entries for this file.  */
      for (f = file->double_colon; f != 0; f = f->next)
	f->last_mtime = file->last_mtime;
    }

  if (file->update_status != -1)
    /* We actually tried to update FILE, which has
       updated its also_make's as well (if it worked).
       If it didn't work, it wouldn't work again for them.
       So mark them as updated with the same status.  */
    for (d = file->also_make; d != 0; d = d->next)
      {
	d->file->command_state = cs_finished;
	d->file->updated = 1;
	d->file->update_status = file->update_status;

	if (!d->file->phony)
	  /* Fetch the new modification time.
	     We do this instead of just invalidating the cached time
	     so that a vpath_search can happen.  Otherwise, it would
	     never be done because the target is already updated.  */
	  (void) f_mtime (d->file, 0);
      }
}

/* Check whether another file (whose mtime is THIS_MTIME)
   needs updating on account of a dependency which is file FILE.
   If it does, store 1 in *MUST_MAKE_PTR.
   In the process, update any non-intermediate files
   that FILE depends on (including FILE itself).
   Return nonzero if any updating failed.  */

static int
check_dep (file, depth, this_mtime, must_make_ptr)
     struct file *file;
     unsigned int depth;
     time_t this_mtime;
     int *must_make_ptr;
{
  register struct dep *d;
  int dep_status = 0;

  ++depth;
  file->updating = 1;

  if (!file->intermediate)
    /* If this is a non-intermediate file, update it and record
       whether it is newer than THIS_MTIME.  */
    {
      time_t mtime;
      dep_status = update_file (file, depth);
      check_renamed (file);
      mtime = file_mtime (file);
      check_renamed (file);
      if (mtime == (time_t) -1 || mtime > this_mtime)
	*must_make_ptr = 1;
    }
  else
    {
      /* FILE is an intermediate file.
	 Update all non-intermediate files we depend on, if necessary,
	 and see whether any of them is more recent than the file
	 on whose behalf we are checking.  */
      register struct dep *lastd;
      lastd = 0;
      d = file->deps;
      while (d != 0)
	{
	  if (d->file->updating)
	    {
	      error ("Circular %s <- %s dependency dropped.",
		     file->name, d->file->name);
	      if (lastd == 0)
		{
		  file->deps = d->next;
		  free ((char *) d);
		  d = file->deps;
		}
	      else
		{
		  lastd->next = d->next;
		  free ((char *) d);
		  d = lastd->next;
		}
	      continue;
	    }

	  d->file->parent = file;
	  dep_status |= check_dep (d->file, depth, this_mtime, must_make_ptr);
	  check_renamed (d->file);
	  if (dep_status != 0 && !keep_going_flag)
	    break;

	  if (d->file->command_state == cs_running
	      || d->file->command_state == cs_deps_running)
	    /* Record that some of FILE's dependencies are still being made.
	       This tells the upper levels to wait on processing it until
	       the commands are finished.  */
	    file->command_state = cs_deps_running;

	  lastd = d;
	  d = d->next;
	}
    }

  file->updating = 0;
  return dep_status;
}

/* Touch FILE.  Return zero if successful, one if not.  */

#define TOUCH_ERROR(call) return (perror_with_name (call, file->name), 1)

static int
touch_file (file)
     register struct file *file;
{
  if (!silent_flag)
    {
      printf ("touch %s\n", file->name);
      fflush (stdout);
    }

#ifndef	NO_ARCHIVES
  if (ar_name (file->name))
    return ar_touch (file->name);
  else
#endif
    {
      int fd = open (file->name, O_RDWR | O_CREAT, 0666);

      if (fd < 0)
	TOUCH_ERROR ("touch: open: ");
      else
	{
	  struct stat statbuf;
	  char buf;

	  if (fstat (fd, &statbuf) < 0)
	    TOUCH_ERROR ("touch: fstat: ");
	  /* Rewrite character 0 same as it already is.  */
	  if (read (fd, &buf, 1) < 0)
	    TOUCH_ERROR ("touch: read: ");
	  if (lseek (fd, 0L, 0) < 0L)
	    TOUCH_ERROR ("touch: lseek: ");
	  if (write (fd, &buf, 1) < 0)
	    TOUCH_ERROR ("touch: write: ");
	  /* If file length was 0, we just
	     changed it, so change it back.  */
	  if (statbuf.st_size == 0)
	    {
	      (void) close (fd);
	      fd = open (file->name, O_RDWR | O_TRUNC, 0666);
	      if (fd < 0)
		TOUCH_ERROR ("touch: open: ");
	    }
	  (void) close (fd);
	}
    }

  return 0;
}

/* Having checked and updated the dependencies of FILE,
   do whatever is appropriate to remake FILE itself.
   Return the status from executing FILE's commands.  */

static void
remake_file (file)
     struct file *file;
{
  if (file->cmds == 0)
    {
      if (file->phony)
	/* Phony target.  Pretend it succeeded.  */
	file->update_status = 0;
      else if (file->is_target)
	/* This is a nonexistent target file we cannot make.
	   Pretend it was successfully remade.  */
	file->update_status = 0;
      else
	{
	  /* This is a dependency file we cannot remake.  Fail.  */
	  static char noway[] = "No rule to make target";
	  if (keep_going_flag || file->dontcare)
	    {
	      if (!file->dontcare)
		error ("*** %s `%s'.", noway, file->name);
 	      file->update_status = 1;
	    }
	  else
	    fatal ("%s `%s'", noway, file->name);
	}
    }
  else
    {
      chop_commands (file->cmds);

      if (!touch_flag || file->cmds->any_recurse)
	{
	  execute_file_commands (file);
	  return;
	}
    }

  /* This does the touching under -t.  */
  notice_finished_file (file);
}

/* Return the mtime of a file, given a `struct file'.
   Caches the time in the struct file to avoid excess stat calls.

   If the file is not found, and SEARCH is nonzero, VPATH searching and
   replacement is done.  If that fails, a library (-lLIBNAME) is tried and
   the library's actual name (/lib/libLIBNAME.a, etc.) is substituted into
   FILE.  */

time_t
f_mtime (file, search)
     register struct file *file;
     int search;
{
  time_t mtime;

  /* File's mtime is not known; must get it from the system.  */

#ifndef	NO_ARCHIVES
  if (ar_name (file->name))
    {
      /* This file is an archive-member reference.  */

      char *arname, *memname;
      struct file *arfile;
      int arname_used = 0;

      /* Find the archive's name.  */
      ar_parse_name (file->name, &arname, &memname);

      /* Find the modification time of the archive itself.
	 Also allow for its name to be changed via VPATH search.  */
      arfile = lookup_file (arname);
      if (arfile == 0)
	{
	  arfile = enter_file (arname);
	  arname_used = 1;
	}
      mtime = f_mtime (arfile, search);
      check_renamed (arfile);
      if (search && strcmp (arfile->name, arname))
	{
	  /* The archive's name has changed.
	     Change the archive-member reference accordingly.  */

	  unsigned int arlen, memlen;

	  if (!arname_used)
	    {
	      free (arname);
	      arname_used = 1;
	    }

	  arname = arfile->name;
	  arlen = strlen (arname);
	  memlen = strlen (memname);

	  free (file->name);

	  file->name = (char *) xmalloc (arlen + 1 + memlen + 2);
	  bcopy (arname, file->name, arlen);
	  file->name[arlen] = '(';
	  bcopy (memname, file->name + arlen + 1, memlen);
	  file->name[arlen + 1 + memlen] = ')';
	  file->name[arlen + 1 + memlen + 1] = '\0';
	}

      if (!arname_used)
	free (arname);
      free (memname);

      if (mtime == (time_t) -1)
	/* The archive doesn't exist, so it's members don't exist either.  */
	return (time_t) -1;

      mtime = ar_member_date (file->name);
    }
  else
#endif
    {
      mtime = name_mtime (file->name);

      if (mtime == (time_t) -1 && search)
	{
	  /* If name_mtime failed, search VPATH.  */
	  char *name = file->name;
	  if (vpath_search (&name, &mtime)
	      /* Last resort, is it a library (-lxxx)?  */
	      || (name[0] == '-' && name[1] == 'l'
		  && library_search (&name, &mtime)))
	    {
	      if (mtime != 0)
		/* vpath_search and library_search store zero in MTIME
		   if they didn't need to do a stat call for their work.  */
		file->last_mtime = mtime;
	      rename_file (file, name);
	      check_renamed (file);
	      return file_mtime (file);
	    }
	}
    }

  /* Store the mtime into all the entries for this file.  */
  if (file->double_colon)
    file = file->double_colon;
  do
    {
      file->last_mtime = mtime;
      file = file->prev;
    } while (file != 0);

  return mtime;
}


/* Return the mtime of the file or archive-member reference NAME.  */

static time_t
name_mtime (name)
     register char *name;
{
  struct stat st;

  if (stat (name, &st) < 0)
    return (time_t) -1;

  return (time_t) st.st_mtime;
}


/* Search for a library file specified as -lLIBNAME, searching for a
   suitable library file in the system library directories and the VPATH
   directories.  */

static int
library_search (lib, mtime_ptr)
     char **lib;
     time_t *mtime_ptr;
{
  static char *dirs[] =
    {
      "/lib",
      "/usr/lib",
      LIBDIR,			/* Defined by configuration.  */
      0
    };

  char *libname = &(*lib)[2];	/* Name without the `-l'.  */
  time_t mtime;

  /* Buffer to construct possible names in.  */
  char *buf = xmalloc (sizeof (LIBDIR) + 8 + strlen (libname) + 4 + 2 + 1);
  char *file, **dp;

  /* Look first for `libNAME.a' in the current directory.  */

  sprintf (buf, "lib%s.a", libname);
  mtime = name_mtime (buf);
  if (mtime != (time_t) -1)
    {
      *lib = buf;
      if (mtime_ptr != 0)
	*mtime_ptr = mtime;
      return 1;
    }

  /* Now try VPATH search on that.  */

  file = buf;
  if (vpath_search (&file, mtime_ptr))
    {
      free (buf);
      *lib = file;
      return 1;
    }

  /* Now try the standard set of directories.  */

  for (dp = dirs; *dp != 0; ++dp)
    {
      sprintf (buf, "%s/lib%s.a", *dp, libname);
      mtime = name_mtime (buf);
      if (mtime != (time_t) -1)
	{
	  *lib = buf;
	  if (mtime_ptr != 0)
	    *mtime_ptr = mtime;
	  return 1;
	}
    }

  free (buf);
  return 0;
}