dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995,1996,1997,1998,1999,2000,2002
   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       if (__asprintf (&buf, result->errcode != 0 ? "%s: %s: %s" : "%s: %s",
  73                       result->objname, _(result->errstring),
  74                       strerror (result->errcode)) != -1)
  75         {
  76           /* We don't need the error string anymore.  */
  77           if (strcmp (result->errstring, "out of memory") != 0)
  78             free ((char *) result->errstring);
  79           result->errstring = buf;
  80         }
  81
  82       /* Mark the error as returned.  */
  83       result->returned = 1;
  84     }
  85
  86   return buf;
  87 }
  88
  89 int
  90 internal_function
  91 _dlerror_run (void (*operate) (void *), void *args)
  92 {
  93   __libc_once_define (static, once);
  94   struct dl_action_result *result;
  95
  96   /* If we have not yet initialized the buffer do it now.  */
  97   __libc_once (once, init);
  98
  99   /* Get error string and number.  */
 100   if (static_buf != NULL)
 101     result = static_buf;
 102   else
 103     {
 104       /* We don't use the static buffer and so we have a key.  Use it
 105          to get the thread-specific buffer.  */
 106       result = __libc_getspecific (key);
 107       if (result == NULL)
 108         {
 109           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 110           if (result == NULL)
 111             /* We are out of memory.  Since this is no really critical
 112                situation we carry on by using the global variable.
 113                This might lead to conflicts between the threads but
 114                they soon all will have memory problems.  */
 115             result = &last_result;
 116           else
 117             /* Set the tsd.  */
 118             __libc_setspecific (key, result);
 119         }
 120     }
 121
 122   if (result->errstring != NULL)
 123     {
 124       /* Free the error string from the last failed command.  This can
 125          happen if `dlerror' was not run after an error was found.  */
 126       if (strcmp (result->errstring, "out of memory") != 0)
 127         free ((char *) result->errstring);
 128       result->errstring = NULL;
 129     }
 130
 131   result->errcode = _dl_catch_error (&result->objname, &result->errstring,
 132                                      operate, args);
 133
 134   /* If no error we mark that no error string is available.  */
 135   result->returned = result->errstring == NULL;
 136
 137   return result->errstring != NULL;
 138 }
 139
 140
 141 /* Initialize buffers for results.  */
 142 static void
 143 init (void)
 144 {
 145   if (__libc_key_create (&key, free_key_mem))
 146     /* Creating the key failed.  This means something really went
 147        wrong.  In any case use a static buffer which is better than
 148        nothing.  */
 149     static_buf = &last_result;
 150 }
 151
 152 static void
 153 __attribute__ ((destructor))
 154 fini (void)
 155 {
 156   if (last_result.errstring != NULL
 157       && strcmp (last_result.errstring, "out of memory") != 0)
 158     free ((char *) last_result.errstring);
 159 }
 160
 161
 162 /* Free the thread specific data, this is done if a thread terminates.  */
 163 static void
 164 free_key_mem (void *mem)
 165 {
 166   struct dl_action_result *result = (struct dl_action_result *) mem;
 167
 168   if (result->errstring != NULL
 169       && strcmp (result->errstring, "out of memory") != 0)
 170     free ((char *) result->errstring);
 171
 172   free (mem);
 173   __libc_setspecific (key, NULL);
 174 }