/* Miscellaneous generic support functions for GNU Make.
Copyright (C) 1988-2013 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 3 of the License, 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
this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "makeint.h"
#include "dep.h"
#include "debug.h"

/* GNU make no longer supports pre-ANSI89 environments.  */

#include <stdarg.h>

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

/* Compare strings *S1 and *S2.
   Return negative if the first is less, positive if it is greater,
   zero if they are equal.  */

int
alpha_compare (const void *v1, const void *v2)
{
  const char *s1 = *((char **)v1);
  const char *s2 = *((char **)v2);

  if (*s1 != *s2)
    return *s1 - *s2;
  return strcmp (s1, s2);
}

/* Discard each backslash-newline combination from LINE.
   Backslash-backslash-newline combinations become backslash-newlines.
   This is done by copying the text at LINE into itself.  */

void
collapse_continuations (char *line)
{
  register char *in, *out, *p;
  register int backslash;
  register unsigned int bs_write;

  in = strchr (line, '\n');
  if (in == 0)
    return;

  out = in;
  while (out > line && out[-1] == '\\')
    --out;

  while (*in != '\0')
    {
      /* BS_WRITE gets the number of quoted backslashes at
         the end just before IN, and BACKSLASH gets nonzero
         if the next character is quoted.  */
      backslash = 0;
      bs_write = 0;
      for (p = in - 1; p >= line && *p == '\\'; --p)
        {
          if (backslash)
            ++bs_write;
          backslash = !backslash;

          /* It should be impossible to go back this far without exiting,
             but if we do, we can't get the right answer.  */
          if (in == out - 1)
            abort ();
        }

      /* Output the appropriate number of backslashes.  */
      while (bs_write-- > 0)
        *out++ = '\\';

      /* Skip the newline.  */
      ++in;

      if (backslash)
        {
          /* Backslash/newline handling:
             In traditional GNU make all trailing whitespace, consecutive
             backslash/newlines, and any leading whitespace on the next line
             is reduced to a single space.
             In POSIX, each backslash/newline and is replaced by a space.  */
          in = next_token (in);
          if (! posix_pedantic)
            while (out > line && isblank ((unsigned char)out[-1]))
              --out;
          *out++ = ' ';
        }
      else
        /* If the newline isn't quoted, put it in the output.  */
        *out++ = '\n';

      /* Now copy the following line to the output.
         Stop when we find backslashes followed by a newline.  */
      while (*in != '\0')
        if (*in == '\\')
          {
            p = in + 1;
            while (*p == '\\')
              ++p;
            if (*p == '\n')
              {
                in = p;
                break;
              }
            while (in < p)
              *out++ = *in++;
          }
        else
          *out++ = *in++;
    }

  *out = '\0';
}

/* Print N spaces (used in debug for target-depth).  */

void
print_spaces (unsigned int n)
{
  while (n-- > 0)
    putchar (' ');
}


/* Return a string whose contents concatenate the NUM strings provided
   This string lives in static, re-used memory.  */

const char *
concat (unsigned int num, ...)
{
  static unsigned int rlen = 0;
  static char *result = NULL;
  unsigned int ri = 0;
  va_list args;

  va_start (args, num);

  while (num-- > 0)
    {
      const char *s = va_arg (args, const char *);
      unsigned int l = s ? strlen (s) : 0;

      if (l == 0)
        continue;

      if (ri + l > rlen)
        {
          rlen = ((rlen ? rlen : 60) + l) * 2;
          result = xrealloc (result, rlen);
        }

      memcpy (result + ri, s, l);
      ri += l;
    }

  va_end (args);

  /* Get some more memory if we don't have enough space for the
     terminating '\0'.   */
  if (ri == rlen)
    {
      rlen = (rlen ? rlen : 60) * 2;
      result = xrealloc (result, rlen);
    }

  result[ri] = '\0';

  return result;
}


/* Return a formatted string buffer.
   LENGTH must be the maximum length of all format arguments, stringified.
   If we had a standard-compliant vsnprintf() this would be a lot simpler.
   Maybe in the future we'll include gnulib's version.  */

const char *
message_s (unsigned int length, int prefix, const char *fmt, ...)
{
  static char *buffer = NULL;
  static unsigned int bsize = 0;
  char *bp;
  va_list args;

  /* Compute the maximum buffer size we'll need, and make sure we have it.  */
  length += strlen (fmt) + strlen (program) + 4 + INTEGER_LENGTH + 2;
  if (length > bsize)
    {
      bsize = length * 2;
      buffer = xrealloc (buffer, bsize);
    }

  bp = buffer;
  if (prefix)
    {
      if (makelevel == 0)
        sprintf (bp, "%s: ", program);
      else
        sprintf (bp, "%s[%u]: ", program, makelevel);
      bp += strlen (buffer);
    }

  va_start (args, fmt);
  vsprintf (bp, fmt, args);
  va_end (args);

  return buffer;
}

/* Return a formatted error message in a buffer.
   LENGTH must be the maximum length of all format arguments, stringified.  */

const char *
error_s (unsigned int length, const gmk_floc *flocp, const char *fmt, ...)
{
  static char *buffer = NULL;
  static unsigned int bsize = 0;
  char *bp;
  va_list args;

  /* Compute the maximum buffer size we'll need, and make sure we have it.  */
  length += (strlen (fmt) + strlen (program) + 4 + INTEGER_LENGTH + 2
             + (flocp && flocp->filenm ? strlen (flocp->filenm) : 0));
  if (length > bsize)
    {
      bsize = length * 2;
      buffer = xrealloc (buffer, bsize);
    }

  bp = buffer;
  if (flocp && flocp->filenm)
    sprintf (bp, "%s:%lu: ", flocp->filenm, flocp->lineno);
  else if (makelevel == 0)
    sprintf (bp, "%s: ", program);
  else
    sprintf (bp, "%s[%u]: ", program, makelevel);
  bp += strlen (bp);

  va_start (args, fmt);
  vsprintf (bp, fmt, args);
  va_end (args);

  return buffer;
}

/* Print a message on stdout.  We could use message_s() to format it but then
   we'd need a va_list version...  */

void
message (int prefix, const char *fmt, ...)
{
  va_list args;

  log_working_directory (1, 0);

  if (fmt != 0)
    {
      if (prefix)
        {
          if (makelevel == 0)
            printf ("%s: ", program);
          else
            printf ("%s[%u]: ", program, makelevel);
        }
      va_start (args, fmt);
      vfprintf (stdout, fmt, args);
      va_end (args);
      putchar ('\n');
    }

  fflush (stdout);
}

/* Print an error message.  */

void
error (const gmk_floc *flocp, const char *fmt, ...)
{
  va_list args;

  log_working_directory (1, 0);

  if (flocp && flocp->filenm)
    fprintf (stderr, "%s:%lu: ", flocp->filenm, flocp->lineno);
  else if (makelevel == 0)
    fprintf (stderr, "%s: ", program);
  else
    fprintf (stderr, "%s[%u]: ", program, makelevel);

  va_start (args, fmt);
  vfprintf (stderr, fmt, args);
  va_end (args);

  putc ('\n', stderr);
  fflush (stderr);
}

/* Print an error message and exit.  */

void
fatal (const gmk_floc *flocp, const char *fmt, ...)
{
  va_list args;

  log_working_directory (1, 0);

  if (flocp && flocp->filenm)
    fprintf (stderr, "%s:%lu: *** ", flocp->filenm, flocp->lineno);
  else if (makelevel == 0)
    fprintf (stderr, "%s: *** ", program);
  else
    fprintf (stderr, "%s[%u]: *** ", program, makelevel);

  va_start (args, fmt);
  vfprintf (stderr, fmt, args);
  va_end (args);

  fputs (_(".  Stop.\n"), stderr);

  log_working_directory (0, 1);

  die (2);
}

#ifndef HAVE_STRERROR

#undef  strerror

char *
strerror (int errnum)
{
  extern int errno, sys_nerr;
#ifndef __DECC
  extern char *sys_errlist[];
#endif
  static char buf[] = "Unknown error 12345678901234567890";

  if (errno < sys_nerr)
    return sys_errlist[errnum];

  sprintf (buf, _("Unknown error %d"), errnum);
  return buf;
}
#endif

/* Print an error message from errno.  */

void
perror_with_name (const char *str, const char *name)
{
  error (NILF, _("%s%s: %s"), str, name, strerror (errno));
}

/* Print an error message from errno and exit.  */

void
pfatal_with_name (const char *name)
{
  fatal (NILF, _("%s: %s"), name, strerror (errno));

  /* NOTREACHED */
}

/* Like malloc but get fatal error if memory is exhausted.  */
/* Don't bother if we're using dmalloc; it provides these for us.  */

#ifndef HAVE_DMALLOC_H

#undef xmalloc
#undef xcalloc
#undef xrealloc
#undef xstrdup

void *
xmalloc (unsigned int size)
{
  /* Make sure we don't allocate 0, for pre-ISO implementations.  */
  void *result = malloc (size ? size : 1);
  if (result == 0)
    fatal (NILF, _("virtual memory exhausted"));
  return result;
}


void *
xcalloc (unsigned int size)
{
  /* Make sure we don't allocate 0, for pre-ISO implementations.  */
  void *result = calloc (size ? size : 1, 1);
  if (result == 0)
    fatal (NILF, _("virtual memory exhausted"));
  return result;
}


void *
xrealloc (void *ptr, unsigned int size)
{
  void *result;

  /* Some older implementations of realloc() don't conform to ISO.  */
  if (! size)
    size = 1;
  result = ptr ? realloc (ptr, size) : malloc (size);
  if (result == 0)
    fatal (NILF, _("virtual memory exhausted"));
  return result;
}


char *
xstrdup (const char *ptr)
{
  char *result;

#ifdef HAVE_STRDUP
  result = strdup (ptr);
#else
  result = malloc (strlen (ptr) + 1);
#endif

  if (result == 0)
    fatal (NILF, _("virtual memory exhausted"));

#ifdef HAVE_STRDUP
  return result;
#else
  return strcpy (result, ptr);
#endif
}

#endif  /* HAVE_DMALLOC_H */

char *
xstrndup (const char *str, unsigned int length)
{
  char *result;

#ifdef HAVE_STRNDUP
  result = strndup (str, length);
  if (result == 0)
    fatal (NILF, _("virtual memory exhausted"));
#else
  result = xmalloc (length + 1);
  if (length > 0)
    strncpy (result, str, length);
  result[length] = '\0';
#endif

  return result;
}


/* Limited INDEX:
   Search through the string STRING, which ends at LIMIT, for the character C.
   Returns a pointer to the first occurrence, or nil if none is found.
   Like INDEX except that the string searched ends where specified
   instead of at the first null.  */

char *
lindex (const char *s, const char *limit, int c)
{
  while (s < limit)
    if (*s++ == c)
      return (char *)(s - 1);

  return 0;
}

/* Return the address of the first whitespace or null in the string S.  */

char *
end_of_token (const char *s)
{
  while (! STOP_SET (*s, MAP_BLANK|MAP_NUL))
    ++s;
  return (char *)s;
}

/* Return the address of the first nonwhitespace or null in the string S.  */

char *
next_token (const char *s)
{
  while (isblank ((unsigned char)*s))
    ++s;
  return (char *)s;
}

/* Find the next token in PTR; return the address of it, and store the length
   of the token into *LENGTHPTR if LENGTHPTR is not nil.  Set *PTR to the end
   of the token, so this function can be called repeatedly in a loop.  */

char *
find_next_token (const char **ptr, unsigned int *lengthptr)
{
  const char *p = next_token (*ptr);

  if (*p == '\0')
    return 0;

  *ptr = end_of_token (p);
  if (lengthptr != 0)
    *lengthptr = *ptr - p;

  return (char *)p;
}


/* Copy a chain of 'struct dep'.  For 2nd expansion deps, dup the name.  */

struct dep *
copy_dep_chain (const struct dep *d)
{
  struct dep *firstnew = 0;
  struct dep *lastnew = 0;

  while (d != 0)
    {
      struct dep *c = xmalloc (sizeof (struct dep));
      memcpy (c, d, sizeof (struct dep));

      if (c->need_2nd_expansion)
        c->name = xstrdup (c->name);

      c->next = 0;
      if (firstnew == 0)
        firstnew = lastnew = c;
      else
        lastnew = lastnew->next = c;

      d = d->next;
    }

  return firstnew;
}

/* Free a chain of 'struct dep'.  */

void
free_dep_chain (struct dep *d)
{
  while (d != 0)
    {
      struct dep *df = d;
      d = d->next;
      free_dep (df);
    }
}

/* Free a chain of struct nameseq.
   For struct dep chains use free_dep_chain.  */

void
free_ns_chain (struct nameseq *ns)
{
  while (ns != 0)
    {
      struct nameseq *t = ns;
      ns = ns->next;
      free (t);
    }
}


#if !HAVE_STRCASECMP && !HAVE_STRICMP && !HAVE_STRCMPI

/* If we don't have strcasecmp() (from POSIX), or anything that can substitute
   for it, define our own version.  */

int
strcasecmp (const char *s1, const char *s2)
{
  while (1)
    {
      int c1 = (int) *(s1++);
      int c2 = (int) *(s2++);

      if (isalpha (c1))
        c1 = tolower (c1);
      if (isalpha (c2))
        c2 = tolower (c2);

      if (c1 != '\0' && c1 == c2)
        continue;

      return (c1 - c2);
    }
}
#endif

#if !HAVE_STRNCASECMP && !HAVE_STRNICMP && !HAVE_STRNCMPI

/* If we don't have strncasecmp() (from POSIX), or anything that can
   substitute for it, define our own version.  */

int
strncasecmp (const char *s1, const char *s2, int n)
{
  while (n-- > 0)
    {
      int c1 = (int) *(s1++);
      int c2 = (int) *(s2++);

      if (isalpha (c1))
        c1 = tolower (c1);
      if (isalpha (c2))
        c2 = tolower (c2);

      if (c1 != '\0' && c1 == c2)
        continue;

      return (c1 - c2);
    }

  return 0;
}
#endif

#ifdef  GETLOADAVG_PRIVILEGED

#ifdef POSIX

/* Hopefully if a system says it's POSIX.1 and has the setuid and setgid
   functions, they work as POSIX.1 says.  Some systems (Alpha OSF/1 1.2,
   for example) which claim to be POSIX.1 also have the BSD setreuid and
   setregid functions, but they don't work as in BSD and only the POSIX.1
   way works.  */

#undef HAVE_SETREUID
#undef HAVE_SETREGID

#else   /* Not POSIX.  */

/* Some POSIX.1 systems have the seteuid and setegid functions.  In a
   POSIX-like system, they are the best thing to use.  However, some
   non-POSIX systems have them too but they do not work in the POSIX style
   and we must use setreuid and setregid instead.  */

#undef HAVE_SETEUID
#undef HAVE_SETEGID

#endif  /* POSIX.  */

#ifndef HAVE_UNISTD_H
extern int getuid (), getgid (), geteuid (), getegid ();
extern int setuid (), setgid ();
#ifdef HAVE_SETEUID
extern int seteuid ();
#else
#ifdef  HAVE_SETREUID
extern int setreuid ();
#endif  /* Have setreuid.  */
#endif  /* Have seteuid.  */
#ifdef HAVE_SETEGID
extern int setegid ();
#else
#ifdef  HAVE_SETREGID
extern int setregid ();
#endif  /* Have setregid.  */
#endif  /* Have setegid.  */
#endif  /* No <unistd.h>.  */

/* Keep track of the user and group IDs for user- and make- access.  */
static int user_uid = -1, user_gid = -1, make_uid = -1, make_gid = -1;
#define access_inited   (user_uid != -1)
static enum { make, user } current_access;


/* Under -d, write a message describing the current IDs.  */

static void
log_access (const char *flavor)
{
  if (! ISDB (DB_JOBS))
    return;

  /* All the other debugging messages go to stdout,
     but we write this one to stderr because it might be
     run in a child fork whose stdout is piped.  */

  fprintf (stderr, _("%s: user %lu (real %lu), group %lu (real %lu)\n"),
           flavor, (unsigned long) geteuid (), (unsigned long) getuid (),
           (unsigned long) getegid (), (unsigned long) getgid ());
  fflush (stderr);
}


static void
init_access (void)
{
#ifndef VMS
  user_uid = getuid ();
  user_gid = getgid ();

  make_uid = geteuid ();
  make_gid = getegid ();

  /* Do these ever fail?  */
  if (user_uid == -1 || user_gid == -1 || make_uid == -1 || make_gid == -1)
    pfatal_with_name ("get{e}[gu]id");

  log_access (_("Initialized access"));

  current_access = make;
#endif
}

#endif  /* GETLOADAVG_PRIVILEGED */

/* Give the process appropriate permissions for access to
   user data (i.e., to stat files, or to spawn a child process).  */
void
user_access (void)
{
#ifdef  GETLOADAVG_PRIVILEGED

  if (!access_inited)
    init_access ();

  if (current_access == user)
    return;

  /* We are in "make access" mode.  This means that the effective user and
     group IDs are those of make (if it was installed setuid or setgid).
     We now want to set the effective user and group IDs to the real IDs,
     which are the IDs of the process that exec'd make.  */

#ifdef  HAVE_SETEUID

  /* Modern systems have the seteuid/setegid calls which set only the
     effective IDs, which is ideal.  */

  if (seteuid (user_uid) < 0)
    pfatal_with_name ("user_access: seteuid");

#else   /* Not HAVE_SETEUID.  */

#ifndef HAVE_SETREUID

  /* System V has only the setuid/setgid calls to set user/group IDs.
     There is an effective ID, which can be set by setuid/setgid.
     It can be set (unless you are root) only to either what it already is
     (returned by geteuid/getegid, now in make_uid/make_gid),
     the real ID (return by getuid/getgid, now in user_uid/user_gid),
     or the saved set ID (what the effective ID was before this set-ID
     executable (make) was exec'd).  */

  if (setuid (user_uid) < 0)
    pfatal_with_name ("user_access: setuid");

#else   /* HAVE_SETREUID.  */

  /* In 4BSD, the setreuid/setregid calls set both the real and effective IDs.
     They may be set to themselves or each other.  So you have two alternatives
     at any one time.  If you use setuid/setgid, the effective will be set to
     the real, leaving only one alternative.  Using setreuid/setregid, however,
     you can toggle between your two alternatives by swapping the values in a
     single setreuid or setregid call.  */

  if (setreuid (make_uid, user_uid) < 0)
    pfatal_with_name ("user_access: setreuid");

#endif  /* Not HAVE_SETREUID.  */
#endif  /* HAVE_SETEUID.  */

#ifdef  HAVE_SETEGID
  if (setegid (user_gid) < 0)
    pfatal_with_name ("user_access: setegid");
#else
#ifndef HAVE_SETREGID
  if (setgid (user_gid) < 0)
    pfatal_with_name ("user_access: setgid");
#else
  if (setregid (make_gid, user_gid) < 0)
    pfatal_with_name ("user_access: setregid");
#endif
#endif

  current_access = user;

  log_access (_("User access"));

#endif  /* GETLOADAVG_PRIVILEGED */
}

/* Give the process appropriate permissions for access to
   make data (i.e., the load average).  */
void
make_access (void)
{
#ifdef  GETLOADAVG_PRIVILEGED

  if (!access_inited)
    init_access ();

  if (current_access == make)
    return;

  /* See comments in user_access, above.  */

#ifdef  HAVE_SETEUID
  if (seteuid (make_uid) < 0)
    pfatal_with_name ("make_access: seteuid");
#else
#ifndef HAVE_SETREUID
  if (setuid (make_uid) < 0)
    pfatal_with_name ("make_access: setuid");
#else
  if (setreuid (user_uid, make_uid) < 0)
    pfatal_with_name ("make_access: setreuid");
#endif
#endif

#ifdef  HAVE_SETEGID
  if (setegid (make_gid) < 0)
    pfatal_with_name ("make_access: setegid");
#else
#ifndef HAVE_SETREGID
  if (setgid (make_gid) < 0)
    pfatal_with_name ("make_access: setgid");
#else
  if (setregid (user_gid, make_gid) < 0)
    pfatal_with_name ("make_access: setregid");
#endif
#endif

  current_access = make;

  log_access (_("Make access"));

#endif  /* GETLOADAVG_PRIVILEGED */
}

/* Give the process appropriate permissions for a child process.
   This is like user_access, but you can't get back to make_access.  */
void
child_access (void)
{
#ifdef  GETLOADAVG_PRIVILEGED

  if (!access_inited)
    abort ();

  /* Set both the real and effective UID and GID to the user's.
     They cannot be changed back to make's.  */

#ifndef HAVE_SETREUID
  if (setuid (user_uid) < 0)
    pfatal_with_name ("child_access: setuid");
#else
  if (setreuid (user_uid, user_uid) < 0)
    pfatal_with_name ("child_access: setreuid");
#endif

#ifndef HAVE_SETREGID
  if (setgid (user_gid) < 0)
    pfatal_with_name ("child_access: setgid");
#else
  if (setregid (user_gid, user_gid) < 0)
    pfatal_with_name ("child_access: setregid");
#endif

  log_access (_("Child access"));

#endif  /* GETLOADAVG_PRIVILEGED */
}

#ifdef NEED_GET_PATH_MAX
unsigned int
get_path_max (void)
{
  static unsigned int value;

  if (value == 0)
    {
      long int x = pathconf ("/", _PC_PATH_MAX);
      if (x > 0)
        value = x;
      else
        return MAXPATHLEN;
    }

  return value;
}
#endif


/* Set a file descriptor to be in O_APPEND mode.
   If it fails, just ignore it.  */

void
set_append_mode (int fd)
{
#if defined(F_GETFL) && defined(F_SETFL) && defined(O_APPEND)
  int flags = fcntl (fd, F_GETFL, 0);
  if (flags >= 0)
    fcntl (fd, F_SETFL, flags | O_APPEND);
#endif
}

/* Provide support for temporary files.  */

#ifndef HAVE_STDLIB_H
# ifdef HAVE_MKSTEMP
int mkstemp (char *template);
# else
char *mktemp (char *template);
# endif
#endif

/* This is only used by output-sync, and it may not be portable.  */
#ifdef OUTPUT_SYNC

/* Returns a file descriptor to a temporary file.  The file is automatically
   closed/deleted on exit.  Don't use a FILE* stream.  */
int
open_tmpfd ()
{
  int fd = -1;
  FILE *tfile = tmpfile ();

  if (! tfile)
    pfatal_with_name ("tmpfile");

  /* Create a duplicate so we can close the stream.  */
  fd = dup (fileno (tfile));
  if (fd < 0)
    pfatal_with_name ("dup");

  fclose (tfile);

  set_append_mode (fd);

  return fd;
}

#endif

FILE *
open_tmpfile (char **name, const char *template)
{
#ifdef HAVE_FDOPEN
  int fd;
#endif

#if defined HAVE_MKSTEMP || defined HAVE_MKTEMP
# define TEMPLATE_LEN   strlen (template)
#else
# define TEMPLATE_LEN   L_tmpnam
#endif
  *name = xmalloc (TEMPLATE_LEN + 1);
  strcpy (*name, template);

#if defined HAVE_MKSTEMP && defined HAVE_FDOPEN
  /* It's safest to use mkstemp(), if we can.  */
  fd = mkstemp (*name);
  if (fd == -1)
    return 0;
  return fdopen (fd, "w");
#else
# ifdef HAVE_MKTEMP
  (void) mktemp (*name);
# else
  (void) tmpnam (*name);
# endif

# ifdef HAVE_FDOPEN
  /* Can't use mkstemp(), but guard against a race condition.  */
  fd = open (*name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  if (fd == -1)
    return 0;
  return fdopen (fd, "w");
# else
  /* Not secure, but what can we do?  */
  return fopen (*name, "w");
# endif
#endif
}



/* This code is stolen from gnulib.
   If/when we abandon the requirement to work with K&R compilers, we can
   remove this (and perhaps other parts of GNU make!) and migrate to using
   gnulib directly.

   This is called only through atexit(), which means die() has already been
   invoked.  So, call exit() here directly.  Apparently that works...?
*/

/* Close standard output, exiting with status 'exit_failure' on failure.
   If a program writes *anything* to stdout, that program should close
   stdout and make sure that it succeeds before exiting.  Otherwise,
   suppose that you go to the extreme of checking the return status
   of every function that does an explicit write to stdout.  The last
   printf can succeed in writing to the internal stream buffer, and yet
   the fclose(stdout) could still fail (due e.g., to a disk full error)
   when it tries to write out that buffered data.  Thus, you would be
   left with an incomplete output file and the offending program would
   exit successfully.  Even calling fflush is not always sufficient,
   since some file systems (NFS and CODA) buffer written/flushed data
   until an actual close call.

   Besides, it's wasteful to check the return value from every call
   that writes to stdout -- just let the internal stream state record
   the failure.  That's what the ferror test is checking below.

   It's important to detect such failures and exit nonzero because many
   tools (most notably 'make' and other build-management systems) depend
   on being able to detect failure in other tools via their exit status.  */

void
close_stdout (void)
{
  int prev_fail = ferror (stdout);
  int fclose_fail = fclose (stdout);

  if (prev_fail || fclose_fail)
    {
      if (fclose_fail)
        error (NILF, _("write error: %s"), strerror (errno));
      else
        error (NILF, _("write error"));
      exit (EXIT_FAILURE);
    }
}