dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995, 96, 97, 98, 99, 2000 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 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
  27 /* Type for storing results of dynamic loading actions.  */
  28 struct dl_action_result
  29   {
  30     int errcode;
  31     int returned;
  32     const char *objname;
  33     const char *errstring;
  34   };
  35 static struct dl_action_result last_result;
  36 static struct dl_action_result *static_buf;
  37
  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;
  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           free ((char *) result->errstring);
  65           result->errstring = NULL;
  66         }
  67       buf = NULL;
  68     }
  69   else
  70     {
  71       buf = (char *) result->errstring;
  72       if (result->errcode != 0
  73           && __asprintf (&buf, "%s: %s: %s",
  74                          result->objname, _(result->errstring),
  75                          strerror (result->errcode)) != -1)
  76         {
  77           /* We don't need the error string anymore.  */
  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       free ((char *) result->errstring);
 127       result->errstring = NULL;
 128     }
 129
 130   result->errcode = _dl_catch_error (&result->objname, &result->errstring,
 131                                      operate, args);
 132
 133   /* If no error we mark that no error string is available.  */
 134   result->returned = result->errstring == NULL;
 135
 136   return result->errstring != NULL;
 137 }
 138
 139
 140 /* Initialize buffers for results.  */
 141 static void
 142 init (void)
 143 {
 144   if (__libc_key_create (&key, free_key_mem))
 145     /* Creating the key failed.  This means something really went
 146        wrong.  In any case use a static buffer which is better than
 147        nothing.  */
 148     static_buf = &last_result;
 149 }
 150
 151
 152 /* Free the thread specific data, this is done if a thread terminates.  */
 153 static void
 154 free_key_mem (void *mem)
 155 {
 156   free (mem);
 157   __libc_setspecific (key, NULL);
 158 }