dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995-2000,2002,2003,2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <libintl.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <bits/libc-lock.h>
  26 #include <ldsodefs.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 __libc_once_define (static, once);
  42
  43 /* Destructor for the thread-specific data.  */
  44 static void init (void);
  45 static void free_key_mem (void *mem);
  46
  47
  48 char *
  49 dlerror (void)
  50 {
  51   char *buf = NULL;
  52   struct dl_action_result *result;
  53
  54   /* If we have not yet initialized the buffer do it now.  */
  55   __libc_once (once, init);
  56
  57   /* Get error string.  */
  58   result = (struct dl_action_result *) __libc_getspecific (key);
  59   if (result == NULL)
  60     result = &last_result;
  61
  62   /* Test whether we already returned the string.  */
  63   if (result->returned != 0)
  64     {
  65       /* We can now free the string.  */
  66       if (result->errstring != NULL)
  67         {
  68           if (strcmp (result->errstring, "out of memory") != 0)
  69             free ((char *) result->errstring);
  70           result->errstring = NULL;
  71         }
  72     }
  73   else if (result->errstring != NULL)
  74     {
  75       buf = (char *) result->errstring;
  76       int n;
  77       if (result->errcode == 0)
  78         n = __asprintf (&buf, "%s%s%s",
  79                         result->objname,
  80                         result->objname[0] == '\0' ? "" : ": ",
  81                         _(result->errstring));
  82       else
  83         n = __asprintf (&buf, "%s%s%s: %s",
  84                         result->objname,
  85                         result->objname[0] == '\0' ? "" : ": ",
  86                         _(result->errstring),
  87                         strerror (result->errcode));
  88       if (n != -1)
  89         {
  90           /* We don't need the error string anymore.  */
  91           if (strcmp (result->errstring, "out of memory") != 0)
  92             free ((char *) result->errstring);
  93           result->errstring = buf;
  94         }
  95
  96       /* Mark the error as returned.  */
  97       result->returned = 1;
  98     }
  99
 100   return buf;
 101 }
 102
 103 int
 104 internal_function
 105 _dlerror_run (void (*operate) (void *), void *args)
 106 {
 107   struct dl_action_result *result;
 108
 109   /* If we have not yet initialized the buffer do it now.  */
 110   __libc_once (once, init);
 111
 112   /* Get error string and number.  */
 113   if (static_buf != NULL)
 114     result = static_buf;
 115   else
 116     {
 117       /* We don't use the static buffer and so we have a key.  Use it
 118          to get the thread-specific buffer.  */
 119       result = __libc_getspecific (key);
 120       if (result == NULL)
 121         {
 122           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 123           if (result == NULL)
 124             /* We are out of memory.  Since this is no really critical
 125                situation we carry on by using the global variable.
 126                This might lead to conflicts between the threads but
 127                they soon all will have memory problems.  */
 128             result = &last_result;
 129           else
 130             /* Set the tsd.  */
 131             __libc_setspecific (key, result);
 132         }
 133     }
 134
 135   if (result->errstring != NULL)
 136     {
 137       /* Free the error string from the last failed command.  This can
 138          happen if `dlerror' was not run after an error was found.  */
 139       if (strcmp (result->errstring, "out of memory") != 0)
 140         free ((char *) result->errstring);
 141       result->errstring = NULL;
 142     }
 143
 144   result->errcode = GLRO(dl_catch_error) (&result->objname, &result->errstring,
 145                                           operate, args);
 146
 147   /* If no error we mark that no error string is available.  */
 148   result->returned = result->errstring == NULL;
 149
 150   return result->errstring != NULL;
 151 }
 152
 153
 154 /* Initialize buffers for results.  */
 155 static void
 156 init (void)
 157 {
 158   if (__libc_key_create (&key, free_key_mem))
 159     /* Creating the key failed.  This means something really went
 160        wrong.  In any case use a static buffer which is better than
 161        nothing.  */
 162     static_buf = &last_result;
 163 }
 164
 165 static void
 166 __attribute__ ((destructor))
 167 fini (void)
 168 {
 169   if (last_result.errstring != NULL
 170       && strcmp (last_result.errstring, "out of memory") != 0)
 171     free ((char *) last_result.errstring);
 172 }
 173
 174
 175 /* Free the thread specific data, this is done if a thread terminates.  */
 176 static void
 177 free_key_mem (void *mem)
 178 {
 179   struct dl_action_result *result = (struct dl_action_result *) mem;
 180
 181   if (result->errstring != NULL
 182       && strcmp (result->errstring, "out of memory") != 0)
 183     free ((char *) result->errstring);
 184
 185   free (mem);
 186   __libc_setspecific (key, NULL);
 187 }