util.c   [plain text]

/* -*- c-file-style: "java"; indent-tabs-mode: nil; tab-width: 4; fill-column: 78 -*-
 *
 * distcc -- A simple distributed compiler system
 *
 * Copyright (C) 2002, 2003 by Martin Pool <mbp@samba.org>
 * Copyright 2007 Google Inc.
 *
 * This program 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
 * of the License, or (at your option) any later version.
 *
 * This program 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 */

#include <config.h>

#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <netdb.h>
#include <ctype.h>

#include <sys/stat.h>
#include <sys/time.h>

#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif

#ifdef HAVE_SYS_LOADAVG_H
#include <sys/loadavg.h>
#endif

#include <sys/param.h>

#include "distcc.h"
#include "trace.h"
#include "util.h"
#include "exitcode.h"
#include "snprintf.h"

            /* I will make a man more precious than fine
             * gold; even a man than the golden wedge of
             * Ophir.
             *        -- Isaiah 13:12 */


void dcc_exit(int exitcode)
{
    struct rusage self_ru, children_ru;

    if (getrusage(RUSAGE_SELF, &self_ru)) {
        rs_log_warning("getrusage(RUSAGE_SELF) failed: %s", strerror(errno));
        memset(&self_ru, 0, sizeof self_ru);
    }
    if (getrusage(RUSAGE_CHILDREN, &children_ru)) {
        rs_log_warning("getrusage(RUSAGE_CHILDREN) failed: %s", strerror(errno));
        memset(&children_ru, 0, sizeof children_ru);
    }

    /* NB fields must match up for microseconds */
    rs_log(RS_LOG_INFO,
           "exit: code %d; self: %d.%06d user %d.%06d sys; children: %d.%06d user %d.%06d sys",
           exitcode,
           (int) self_ru.ru_utime.tv_sec, (int) self_ru.ru_utime.tv_usec,
           (int) self_ru.ru_stime.tv_sec, (int) self_ru.ru_stime.tv_usec,
           (int) children_ru.ru_utime.tv_sec, (int) children_ru.ru_utime.tv_usec,
           (int) children_ru.ru_stime.tv_sec, (int)  children_ru.ru_stime.tv_usec);

    exit(exitcode);
}


int str_endswith(const char *tail, const char *tiger)
{
    size_t len_tail = strlen(tail);
    size_t len_tiger = strlen(tiger);

    if (len_tail > len_tiger)
        return 0;

    return !strcmp(tiger + len_tiger - len_tail, tail);
}


int str_startswith(const char *head, const char *worm)
{
    return !strncmp(head, worm, strlen(head));
}



/**
 * Skim through NULL-terminated @p argv, looking for @p s.
 **/
int argv_contains(char **argv, const char *s)
{
    while (*argv) {
        if (!strcmp(*argv, s))
            return 1;
        argv++;
    }
    return 0;
}


/**
 * Redirect a file descriptor into (or out of) a file.
 *
 * Used, for example, to catch compiler error messages into a
 * temporary file.
 **/
int dcc_redirect_fd(int fd, const char *fname, int mode)
{
    int newfd;

    /* ignore errors */
    close(fd);

    newfd = open(fname, mode, 0666);
    if (newfd == -1) {
        rs_log_crit("failed to reopen fd%d onto %s: %s",
                    fd, fname, strerror(errno));
        return EXIT_IO_ERROR;
    } else if (newfd != fd) {
        rs_log_crit("oops, reopened fd%d onto fd%d?", fd, newfd);
        return EXIT_IO_ERROR;
    }

    return 0;
}



char *dcc_gethostname(void)
{
    static char myname[100] = "\0";

    if (!myname[0]) {
        if (gethostname(myname, sizeof myname - 1) == -1)
            strcpy(myname, "UNKNOWN");
    }

    return myname;
}


/**
 * Look up a boolean environment option, which must be either "0" or
 * "1".  The default, if it's not set or is empty, is @p default.
 **/
int dcc_getenv_bool(const char *name, int default_value)
{
    const char *e;

    e = getenv(name);
    if (!e || !*e)
        return default_value;
    if (!strcmp(e, "1"))
        return 1;
    else if (!strcmp(e, "0"))
        return 0;
    else
        return default_value;
}


#define IS_LEGAL_DOMAIN_CHAR(c) (isalnum(c) || ((c) == '-') || ((c) == '.'))

/* Copy domain part of hostname to static buffer.
 * If hostname has no domain part, returns -1.
 * If domain lookup fails, returns -1.
 * Otherwise places pointer to domain in *domain_name and returns 0.
 *
 * This should yield the same result as the linux command
 * 'dnsdomainname' or 'hostname -d'.
 **/
int dcc_get_dns_domain(const char **domain_name)
{
#if 0 /* Too expensive */

    static char host_name[1024];
    struct hostent *h;
    int ret;

    ret = gethostname(host_name, sizeof(host_name));
    if (ret != 0)
        return -1;

    h = gethostbyname(host_name);
    if (h == NULL) {
        rs_log_error("failed to look up self \"%s\": %s", host_name,
                     hstrerror(h_errno));
        return -1;
    }

    strncpy(host_name, h->h_name, sizeof(host_name));
    *domain_name = strchr(h->h_name, '.');

#else  /* cheaper */
    const char *envh, *envh2;
    int i;
    const int MAXDOMAINLEN = 512;

    /* Kludge for speed: Try to retrieve FQDN from environment.
     * This can save many milliseconds on a network that's busy and lossy
     * (glibc retries DNS operations very slowly).
     */

    /* Solaris, BSD tend to put it in HOST.
     * (Some flavors of Linux put the non-qualified hostname in HOST,
     *  so ignore this if it doesn't have a dot in it.)
     */
    envh = getenv("HOST");
    if (envh && !strchr(envh, '.'))
        envh = NULL;

    /* Some flavors of Linux put the FQDN in HOSTNAME when
     * logged in interactively, but not when ssh'd in noninteractively.
     * Ubuntu's bash puts it in HOSTNAME but doesn't export it!
     */
    envh2 = getenv("HOSTNAME");
    if (envh2 && !strchr(envh2, '.'))
        envh2 = NULL;

    /* Pick the 'better' of the two.  Longer is usually better. */
    if (envh2 && (!envh || (strlen(envh) < strlen(envh2))))
        envh = envh2;

    /* If the above didn't work out, fall back to the real way. */
    if (!envh || !strchr(envh, '.')) {
        static char host_name[1024];
        struct hostent *h;
        int ret;

        ret = gethostname(host_name, sizeof(host_name));
        if (ret != 0)
            return -1;

        /* If hostname has a dot in it, assume it's the DNS address */
        if (!strchr(host_name, '.')) {
            /* Otherwise ask DNS what our full hostname is */
            h = gethostbyname(host_name);
            if (h == NULL) {
                rs_log_error("failed to look up self \"%s\": %s", host_name,
                             hstrerror(h_errno));
                return -1;
            }
            strncpy(host_name, h->h_name, sizeof(host_name));
        }
        envh = host_name;
    }

    /* validate to avoid possible errors from bad chars or huge value */
    for (i=0; envh[i] != '\0'; i++) {
        if (i > MAXDOMAINLEN || !IS_LEGAL_DOMAIN_CHAR(envh[i])) {
            rs_log_error("HOST/HOSTNAME present in environment but illegal: '%s'", envh);
            return -1;
        }
    }
    *domain_name = strchr(envh, '.');
#endif

    if (*domain_name == NULL)
        return -1;

    (*domain_name)++;
    /* Return 0 on success, or -1 if the domain name is illegal, e.g. empty */
    return ((*domain_name)[0] == '\0') ? -1 : 0;
}



/**
 * Set the `FD_CLOEXEC' flag of DESC if VALUE is nonzero,
 * or clear the flag if VALUE is 0.
 *
 * From the GNU C Library examples.
 *
 * @returns 0 on success, or -1 on error with `errno' set.
 **/
int set_cloexec_flag (int desc, int value)
{
    int oldflags = fcntl (desc, F_GETFD, 0);
    /* If reading the flags failed, return error indication now. */
    if (oldflags < 0)
        return oldflags;
    /* Set just the flag we want to set. */
    if (value != 0)
        oldflags |= FD_CLOEXEC;
    else
        oldflags &= ~FD_CLOEXEC;
    /* Store modified flag word in the descriptor. */
    return fcntl (desc, F_SETFD, oldflags);
}


/**
 * Ignore or unignore SIGPIPE.
 *
 * The server and child ignore it, because distcc code wants to see
 * EPIPE errors if something goes wrong.  However, for invoked
 * children it is set back to the default value, because they may not
 * handle the error properly.
 **/
int dcc_ignore_sigpipe(int val)
{
    if (signal(SIGPIPE, val ? SIG_IGN : SIG_DFL) == SIG_ERR) {
        rs_log_warning("signal(SIGPIPE, %s) failed: %s",
                       val ? "ignore" : "default",
                       strerror(errno));
        return EXIT_DISTCC_FAILED;
    }
    return 0;
}

/**
 * Search through the $PATH looking for a directory containing a file called
 * @p compiler_name, which is a symbolic link containing the string "distcc".
 *
 * Trim the path to just after the *last* such directory.
 *
 * If we find a distcc masquerade dir on the PATH, remove all the dirs up
 * to that point.
 **/
int dcc_trim_path(const char *compiler_name)
{
    const char *envpath, *newpath, *p, *n;
    char linkbuf[MAXPATHLEN], *buf;
    struct stat sb;
    size_t len;

    if (!(envpath = getenv("PATH"))) {
        rs_trace("PATH seems not to be defined");
        return 0;
    }

    rs_trace("original PATH %s", envpath);
    rs_trace("looking for \"%s\"", compiler_name);

    /* Allocate a buffer that will let us append "/cc" onto any PATH
     * element, even if there is only one item in the PATH. */
    if (!(buf = malloc(strlen(envpath)+1+strlen(compiler_name)+1))) {
        rs_log_error("failed to allocate buffer for PATH munging");
        return EXIT_OUT_OF_MEMORY;
    }

    for (n = p = envpath, newpath = NULL; *n; p = n) {
        n = strchr(p, ':');
        if (n)
            len = n++ - p;
        else {
            len = strlen(p);
            n = p + len;
        }
        strncpy(buf, p, len);

        sprintf(buf + len, "/%s", compiler_name);
        if (lstat(buf, &sb) == -1)
            continue;           /* ENOENT, EACCESS, etc */
        if (!S_ISLNK(sb.st_mode))
            break;
        if ((len = readlink(buf, linkbuf, sizeof linkbuf)) <= 0)
            continue;
        linkbuf[len] = '\0';
        if (strstr(linkbuf, "distcc")) {
            /* Set newpath to the part of the PATH past our match. */
            newpath = n;
        }
    }

    if (newpath) {
        int ret = dcc_set_path(newpath);
        if (ret)
            return ret;
    } else
        rs_trace("not modifying PATH");

    free(buf);
    return 0;
}

/* Set the PATH environment variable to the indicated value. */
int dcc_set_path(const char *newpath)
{
    char *buf;

    if (asprintf(&buf, "PATH=%s", newpath) <= 0 || !buf) {
        rs_log_error("failed to allocate buffer for new PATH");
        return EXIT_OUT_OF_MEMORY;
    }
    rs_trace("setting %s", buf);
    if (putenv(buf) < 0) {
        rs_log_error("putenv PATH failed");
        return EXIT_FAILURE;
    }
    /* We must leave "buf" allocated. */
    return 0;
}

/* Return the supplied path with the current-working directory prefixed (if
 * needed) and all "dir/.." references removed.  Supply path_len if you want
 * to use only a substring of the path string, otherwise make it 0. */
char *dcc_abspath(const char *path, int path_len)
{
    static char buf[MAXPATHLEN];
    unsigned len;
    char *p, *slash;

    if (*path == '/')
        len = 0;
    else {
#ifdef HAVE_GETCWD
        getcwd(buf, sizeof buf);
#else
        getwd(buf);
#endif
        len = strlen(buf);
        if (len >= sizeof buf) {
            rs_log_crit("getwd overflowed in dcc_abspath()");
        }
        buf[len++] = '/';
    }
    if (path_len <= 0)
        path_len = strlen(path);
    if (path_len >= 2 && *path == '.' && path[1] == '/') {
        path += 2;
        path_len -= 2;
    }
    if (len + (unsigned)path_len >= sizeof buf) {
        rs_log_error("path overflowed in dcc_abspath()");
        exit(EXIT_OUT_OF_MEMORY);
    }
    strncpy(buf + len, path, path_len);
    buf[len + path_len] = '\0';
    for (p = buf+len-(len > 0); (p = strstr(p, "/../")) != NULL; p = slash) {
        *p = '\0';
        if (!(slash = strrchr(buf, '/')))
            slash = p;
        strcpy(slash, p+3);
    }
    return buf;
}

/* Return the current number of running processes. */
int dcc_getcurrentload(void) {
#if defined(linux)
  double stats[3];
  int running;
  int total;
  int last_pid;
  int retval;

  FILE *f = fopen("/proc/loadavg", "r");
  if (NULL == f)
      return -1;

  retval = fscanf(f, "%lf %lf %lf %d/%d %d", &stats[0], &stats[1], &stats[2],
                  &running, &total, &last_pid);
  fclose(f);

  if (6 != retval)
      return -1;

  return running;
#else
  return -1;
#endif
}

/**
 *  Wrapper for getloadavg() that tries to return all 3 samples, and reports
 *  -1 for those samples that are not available.
 *
 *  Averages are over the last 1, 5, and 15 minutes, respectively.
 **/
void dcc_getloadavg(double loadavg[3]) {
  int num;
  int i;

#if defined(HAVE_GETLOADAVG)
  num = getloadavg(loadavg, 3);
#else
  num = 0;
#endif

  /* If getloadavg() didn't return 3 we want to fill
   * in the invalid elements with -1 */
  if (num < 0)
      num = 0;

  for (i=num; i < 3; ++i)
      loadavg[i] = -1;
}


/**
 * Duplicate the part of the string @p psrc up to a character in @p sep
 * (or end of string), storing the result in @p pdst.  @p psrc is updated to
 * point to the terminator.  (If the terminator is not found it will
 * therefore point to \0.
 *
 * If there is no more string, then @p pdst is instead set to NULL, no
 * memory is allocated, and @p psrc is not advanced.
 **/
int dcc_dup_part(const char **psrc, char **pdst, const char *sep)
{
    size_t len;

    len = strcspn(*psrc, sep);
    if (len == 0) {
        *pdst = NULL;
    } else {
        if (!(*pdst = malloc(len + 1))) {
            rs_log_error("failed to allocate string duplicate: %d", (int) len);
            return EXIT_OUT_OF_MEMORY;
        }
        strncpy(*pdst, *psrc, len);
        (*pdst)[len] = '\0';
        (*psrc) += len;
    }

    return 0;
}



int dcc_remove_if_exists(const char *fname)
{
    if (unlink(fname) && errno != ENOENT) {
        rs_log_warning("failed to unlink %s: %s", fname,
                       strerror(errno));
        return EXIT_IO_ERROR;
    }
    return 0;
}


/* Returns the number of processes in state D, the max non-cc/c++ RSS in kb and
 * the max RSS program's name */
void dcc_get_proc_stats(int *num_D, int *max_RSS, char **max_RSS_name) {
#if defined(linux)
    DIR *proc = opendir("/proc");
    struct dirent *procsubdir;
    static int pagesize = -1;
    static char RSS_name[1024];
    char statfile[1024];
    FILE *f;
    char name[1024];
    char state;
    int pid;
    int rss_size;
    int l;
    char *c;
    int isCC;

    /* If this doesn't cut it for you, see how CVS does it:
     * http://savannah.nongnu.org/cgi-bin/viewcvs/cvs/ccvs/lib/getpagesize.h */
    if (pagesize == -1) {
#if HAVE_GETPAGESIZE
        pagesize = getpagesize();
#else
        pagesize = 8192;
#endif
    }

    *num_D = 0;
    *max_RSS = 0;
    *max_RSS_name = RSS_name;
    RSS_name[0] = 0;

    while ((procsubdir = readdir(proc)) != NULL) {
        if (sscanf(procsubdir->d_name, "%d", &pid) != 1)
            continue;

        strcpy(statfile, "/proc/");
        strcat(statfile, procsubdir->d_name);
        strcat(statfile, "/stat");

        f = fopen(statfile, "r");
        if (f == NULL)
            continue;

        if (fscanf(f, "%*d %s %c %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %d",
                        name, &state, &rss_size) != 3) {
            fclose(f);
            continue;
        }

        rss_size = (rss_size * pagesize) / 1024; /* get rss_size in KB */

        if (state == 'D') {
            (*num_D)++;
        }

        l = strlen(RSS_name);
        c = RSS_name;

        /* check for .*{++,cc} */
        isCC = (l >= 2) && ((c[l-1] == 'c' && c[l-2] == 'c')
                                || (c[l-1] == '+' && c[l-2] == '+'));
        if ((rss_size > *max_RSS) && !isCC) {
            *max_RSS = rss_size;
            strncpy(RSS_name, name, 1024);
        }

        fclose(f);
    }

    closedir(proc);
#else
    static char RSS_name[] = "none";
    *num_D = -1;
    *max_RSS = -1;
    *max_RSS_name = RSS_name;
#endif
}


/* Returns the number of sector read/writes since boot */
void dcc_get_disk_io_stats(int *n_reads, int *n_writes) {
#if defined(linux)
    int retval;
    int kernel26 = 1;
    FILE *f;
    int reads, writes, minor;
    char dev[100];
    char tmp[1024];

    *n_reads = 0;
    *n_writes = 0;

    f = fopen("/proc/diskstats", "r");
    if (f == NULL) {
        if (errno != ENOENT)
            return;

        /* /proc/diskstats does not exist. probably a 2.4 kernel, so try reading
         * /proc/partitions */
        f = fopen("/proc/partitions", "r");
        if (f == NULL)
            return;
        kernel26 = 0;
    }

    if (!kernel26) /* blast away 2 header lines in /proc/partitions */
        fscanf(f, "%*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s");

    while (1) {
        if (kernel26)
            retval = fscanf(f, " %*d %d %s", &minor, dev);
        else
            retval = fscanf(f, " %*d %d %*d %s", &minor, dev);

        if (retval == EOF || retval != 2)
            break;

        if (minor % 64 == 0
                && ((dev[0] == 'h' && dev[1] == 'd' && dev[2] == 'a')
                    || (dev[0] == 's' && dev[1] == 'd' && dev[2] == 'a'))) {
            /* disk stats */
            retval = fscanf(f, " %*d %*d %d %*d %*d %*d %d %*d %*d %*d %*d",
                            &reads, &writes);
            if (retval == EOF || retval != 2)
                break;

            /* only add stats for disks, so we don't double count */
            *n_reads += reads;
            *n_writes += writes;
        } else {
#if 0
            /* individual parition stats */
            retval = fscanf(f, " %*d %d %*d %d", &reads, &writes);
            if (retval == EOF || retval != 2)
                break;
#endif
            /* assume the lines aren't longer that 1024 characters */
            fgets(tmp, 1024, f);
        }
    }

    fclose(f);
#else
    *n_reads = 0;
    *n_writes = 0;
#endif
}


#ifndef HAVE_STRLCPY
/* like strncpy but does not 0 fill the buffer and always null
   terminates. bufsize is the size of the destination buffer */
 size_t strlcpy(char *d, const char *s, size_t bufsize)
{
    size_t len = strlen(s);
    size_t ret = len;
    if (bufsize <= 0) return 0;
    if (len >= bufsize) len = bufsize-1;
    memcpy(d, s, len);
    d[len] = 0;
    return ret;
}
#endif

#ifndef HAVE_STRSEP
static char* strsep(char** str, const char* delims)
{
    char* token;

    if (*str == NULL) {
        return NULL;
    }

    token = *str;
    while (**str != '\0') {
        if (strchr(delims, **str) != NULL) {
            **str = '\0';
            (*str)++;
            return token;
        }
        (*str)++;
    }
    *str = NULL;
    return token;
}
#endif

/* Given a string @p input, this function fills a
   a newly-allocated array of strings with copies of
   the input's whitespace-separated parts.
   Returns 0 on success, 1 on error.
 */
int dcc_tokenize_string(const char *input, char ***argv_ptr)
{
    size_t n_spaces = 0;
    char *for_count;
    char **ap;
    char *input_copy;

    /* First of all, make a copy of the input string;
     * this way, we can destroy the copy.
     */
    input_copy = strdup(input);
    if (input_copy == NULL)
        return 1;

    /* Count the spaces in the string. */
    for (for_count = input_copy; *for_count; for_count++)
        if (isspace(*for_count))
            n_spaces++;

    /* The maximum number of space-delimited strings we
     * can have is n_spaces + 1, and we need to add another 1 for
     * the null-termination.
     */
    *argv_ptr = malloc(sizeof(char*) * (n_spaces + 1 + 1));
    if (*argv_ptr == NULL) {
        free(input_copy);
        return 1;
    }

    ap = *argv_ptr;
    while((*ap = strsep(&input_copy, " \t\n")) != NULL) {

        /* If the field is empty, do nothing */
      if (**ap == '\0')
          continue;

      *ap = strdup(*ap);
      if (*ap == NULL) {
          char **p;
          for (p = *argv_ptr; *p; p++) {
            free(*p);
          }
          free(*argv_ptr);
          free(input_copy);
          return 1;
      }

      ap++;
    }
    free(input_copy);
    return 0;
}

/* Given a string @p s, this function returns a new string with all
 * occurrences of @p find replaced with the contents of @p replace.
 * If any arguments are missing, or any error occurs, returns NULL.
 */
char *dcc_replace_substring(const char *s,
                            const char *find, const char *replace) {
    int s_left;
    int buf_pos = 0, buf_size = 0;
    char *buf = NULL, *new_buf;
    const char *next;
    int replace_len, find_len;
    int len_change;

    if (!s || !find || !replace) {
        rs_log_error("got NULL arguments");
        goto out_error;
    }
  
    find_len = strlen(find);
    replace_len = strlen(replace);

    if (!find_len) {
        rs_log_error("Asked to replace an empty string");
        goto out_error;
    }
    
    /* This is the number of chars we'll need to add each time we do
     * a replacement.  If replace is shorter then find, we'll catch it
     * with a final realloc when done. */
    len_change = replace_len - find_len;
    if (len_change < 0)
        len_change = 0;

    s_left = strlen(s);
    buf_size = s_left + 1;
    buf = malloc(buf_size * sizeof(char));
    if (!buf) {
        rs_log_error("malloc(%ld) failed: %s",
                     (long)buf_size * sizeof(char), strerror(errno));
        goto out_error;
    }

    /* Loop on matches */
    while ((next = strstr(s, find))) {
        if (len_change) {
            buf_size += len_change;
            new_buf = realloc(buf, buf_size * sizeof(char));
            if (!new_buf) {
                rs_log_error("realloc(%ld) failed: %s",
                             (long)buf_size * sizeof(char), strerror(errno));
                goto out_error;
            }
            buf = new_buf;
        }
        strncpy(buf + buf_pos, s, next - s);
        buf_pos += (next - s);
        s_left -= (next - s);
        strcpy(buf + buf_pos, replace);
        buf_pos += replace_len;
        s_left -= find_len;

        s = next + find_len;
    }
    
    /* Copy over what was left after the last replacement. */
    if (s_left) {
        strcpy(buf + buf_pos, s);
        buf_pos += s_left;
    }

    /* Terminate it. */
    buf[buf_pos++] = '\0';
    
    /* If we shrunk the string, do a final realloc to downsize it
     * to be the right length.  But, we don't fail if this doesn't
     * work because the string will still be ok, just using more
     * memory then needed. */
    if (buf_pos < buf_size) {
        buf_size = buf_pos;
        new_buf = realloc(buf, buf_size * sizeof(char));
        if (new_buf) {
            buf = new_buf;
        } else {
            rs_log_info("realloc(%ld) failed: %s",
                        (long)buf_size * sizeof(char), strerror(errno));
        }
    }

    return buf;

  out_error:

    if (buf)
        free(buf);
    return NULL;
}