xapian-core/common/debuglog.cc

   1 /** @file debuglog.cc
   2  * @brief Debug logging macros.
   3  */
   4 /* Copyright (C) 2008,2011,2012,2014,2015 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <config.h>
  22
  23 #ifdef XAPIAN_DEBUG_LOG
  24
  25 #include "debuglog.h"
  26
  27 #include "errno_to_string.h"
  28 #include "str.h"
  29
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32 #include "safeerrno.h"
  33 #include "safefcntl.h"
  34 #include "safeunistd.h"
  35
  36 #include <cstdlib> // For getenv().
  37 #include <string>
  38
  39 using namespace std;
  40
  41 DebugLogger xapian_debuglogger_;
  42
  43 // We use O_SYNC to attempt to ensure that debug output is written to disk so
  44 // that none is lost if we crash.  Some platforms (e.g. mingw) don't support
  45 // O_SYNC, so on these we just don't use it.
  46 #ifndef O_SYNC
  47 # define O_SYNC 0
  48 #endif
  49
  50 DebugLogger::~DebugLogger()
  51 {
  52     LOGLINE(ALWAYS, PACKAGE_STRING": debug log ended");
  53 }
  54
  55 void
  56 DebugLogger::initialise_categories_mask()
  57 {
  58     fd = -2;
  59     const char * f = getenv("XAPIAN_DEBUG_LOG");
  60     if (f && *f) {
  61         if (f[0] == '-' && f[1] == '\0') {
  62             // Filename "-" means "log to stderr".
  63             fd = 2;
  64         } else {
  65             string fnm, pid;
  66             while (*f) {
  67                 if (*f == '%' && f[1] == 'p') {
  68                     // Replace %p in the filename with the process id.
  69                     if (pid.empty()) pid = str(getpid());
  70                     fnm += pid;
  71                     f += 2;
  72                 } else {
  73                     fnm += *f++;
  74                 }
  75             }
  76
  77             fd = open(fnm.c_str(), O_CREAT|O_WRONLY|O_SYNC|O_APPEND|O_CLOEXEC, 0644);
  78             if (fd == -1) {
  79                 // If we failed to open the log file, report to stderr, but
  80                 // don't spew all the log output to stderr too or else the
  81                 // user will probably miss the message about the debug log
  82                 // failing to open!
  83                 fd = 2;
  84                 string e;
  85                 errno_to_string(errno, e);
  86                 LOGLINE(ALWAYS, PACKAGE_STRING": Failed to open debug log '"
  87                         << fnm << "' (" << e << ')');
  88                 fd = -2;
  89             }
  90         }
  91
  92         if (fd >= 0) {
  93             const char * v = getenv("XAPIAN_DEBUG_FLAGS");
  94             if (v) {
  95                 bool toggle = (*v == '-');
  96                 if (toggle) ++v;
  97                 categories_mask = 0;
  98                 while (*v) {
  99                     int ch = *v++ - '@';
 100                     if (ch > 0 && ch <= 26) categories_mask |= 1ul << ch;
 101                 }
 102                 if (toggle) categories_mask ^= 0xffffffff;
 103             }
 104         }
 105     }
 106     LOGLINE(ALWAYS, PACKAGE_STRING": debug log started");
 107 }
 108
 109 void
 110 DebugLogger::log_line(debuglog_categories category, const string & msg)
 111 {
 112     if (fd < 0) return;
 113
 114     // Preserve errno over logging calls, so they can safely be added to code
 115     // which expects errno not to change.
 116     int saved_errno = errno;
 117
 118     string line;
 119     line.reserve(9 + indent_level + msg.size());
 120     line = char(category) + '@';
 121     line += ' ';
 122     line += str(getpid());
 123     line.append(indent_level + 1, ' ');
 124     line += msg;
 125     line += '\n';
 126
 127     const char * p = line.data();
 128     size_t to_do = line.size();
 129     while (to_do) {
 130         ssize_t n = write(fd, p, to_do);
 131         if (n < 0) {
 132             // Retry if interrupted by a signal.
 133             if (errno == EINTR) continue;
 134
 135             // Upon other errors, close the log file, moan to stderr, and stop
 136             // logging.
 137             (void)close(fd);
 138             fd = 2;
 139             string e;
 140             errno_to_string(errno, e);
 141             LOGLINE(ALWAYS, PACKAGE_STRING": Failed to write log output ("
 142                     << e << ')');
 143             fd = -2;
 144             break;
 145         }
 146         p += n;
 147         to_do -= n;
 148     }
 149
 150     errno = saved_errno;
 151 }
 152
 153 #endif // XAPIAN_DEBUG_LOG