dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995,1996,1997,1998,1999,2000,2002, 2003
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <dlfcn.h>
  22 #include <libintl.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <bits/libc-lock.h>
  27
  28 /* Type for storing results of dynamic loading actions.  */
  29 struct dl_action_result
  30   {
  31     int errcode;
  32     int returned;
  33     const char *objname;
  34     const char *errstring;
  35   };
  36 static struct dl_action_result last_result;
  37 static struct dl_action_result *static_buf;
  38
  39 /* This is the key for the thread specific memory.  */
  40 static __libc_key_t key;
  41
  42 /* Destructor for the thread-specific data.  */
  43 static void init (void);
  44 static void free_key_mem (void *mem);
  45
  46
  47 char *
  48 dlerror (void)
  49 {
  50   char *buf = NULL;
  51   struct dl_action_result *result;
  52
  53   /* Get error string.  */
  54   result = (struct dl_action_result *) __libc_getspecific (key);
  55   if (result == NULL)
  56     result = &last_result;
  57
  58   /* Test whether we already returned the string.  */
  59   if (result->returned != 0)
  60     {
  61       /* We can now free the string.  */
  62       if (result->errstring != NULL)
  63         {
  64           if (strcmp (result->errstring, "out of memory") != 0)
  65             free ((char *) result->errstring);
  66           result->errstring = NULL;
  67         }
  68     }
  69   else if (result->errstring != NULL)
  70     {
  71       buf = (char *) result->errstring;
  72       int n;
  73       if (result->errcode == 0)
  74         n = __asprintf (&buf, "%s%s%s",
  75                         result->objname,
  76                         result->objname[0] == '\0' ? "" : ": ",
  77                         _(result->errstring));
  78       else
  79         n = __asprintf (&buf, "%s%s%s: %s",
  80                         result->objname,
  81                         result->objname[0] == '\0' ? "" : ": ",
  82                         _(result->errstring),
  83                         strerror (result->errcode));
  84       if (n != -1)
  85         {
  86           /* We don't need the error string anymore.  */
  87           if (strcmp (result->errstring, "out of memory") != 0)
  88             free ((char *) result->errstring);
  89           result->errstring = buf;
  90         }
  91
  92       /* Mark the error as returned.  */
  93       result->returned = 1;
  94     }
  95
  96   return buf;
  97 }
  98
  99 int
 100 internal_function
 101 _dlerror_run (void (*operate) (void *), void *args)
 102 {
 103   __libc_once_define (static, once);
 104   struct dl_action_result *result;
 105
 106   /* If we have not yet initialized the buffer do it now.  */
 107   __libc_once (once, init);
 108
 109   /* Get error string and number.  */
 110   if (static_buf != NULL)
 111     result = static_buf;
 112   else
 113     {
 114       /* We don't use the static buffer and so we have a key.  Use it
 115          to get the thread-specific buffer.  */
 116       result = __libc_getspecific (key);
 117       if (result == NULL)
 118         {
 119           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 120           if (result == NULL)
 121             /* We are out of memory.  Since this is no really critical
 122                situation we carry on by using the global variable.
 123                This might lead to conflicts between the threads but
 124                they soon all will have memory problems.  */
 125             result = &last_result;
 126           else
 127             /* Set the tsd.  */
 128             __libc_setspecific (key, result);
 129         }
 130     }
 131
 132   if (result->errstring != NULL)
 133     {
 134       /* Free the error string from the last failed command.  This can
 135          happen if `dlerror' was not run after an error was found.  */
 136       if (strcmp (result->errstring, "out of memory") != 0)
 137         free ((char *) result->errstring);
 138       result->errstring = NULL;
 139     }
 140
 141   result->errcode = _dl_catch_error (&result->objname, &result->errstring,
 142                                      operate, args);
 143
 144   /* If no error we mark that no error string is available.  */
 145   result->returned = result->errstring == NULL;
 146
 147   return result->errstring != NULL;
 148 }
 149
 150
 151 /* Initialize buffers for results.  */
 152 static void
 153 init (void)
 154 {
 155   if (__libc_key_create (&key, free_key_mem))
 156     /* Creating the key failed.  This means something really went
 157        wrong.  In any case use a static buffer which is better than
 158        nothing.  */
 159     static_buf = &last_result;
 160 }
 161
 162 static void
 163 __attribute__ ((destructor))
 164 fini (void)
 165 {
 166   if (last_result.errstring != NULL
 167       && strcmp (last_result.errstring, "out of memory") != 0)
 168     free ((char *) last_result.errstring);
 169 }
 170
 171
 172 /* Free the thread specific data, this is done if a thread terminates.  */
 173 static void
 174 free_key_mem (void *mem)
 175 {
 176   struct dl_action_result *result = (struct dl_action_result *) mem;
 177
 178   if (result->errstring != NULL
 179       && strcmp (result->errstring, "out of memory") != 0)
 180     free ((char *) result->errstring);
 181
 182   free (mem);
 183   __libc_setspecific (key, NULL);
 184 }