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 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
  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 /* This is the key for the thread specific memory.  */
  39 static __libc_key_t key;
  40
  41 /* Destructor for the thread-specific data.  */
  42 static void init (void);
  43 static void free_key_mem (void *mem);
  44
  45
  46 char *
  47 dlerror (void)
  48 {
  49   char *buf = NULL;
  50   struct dl_action_result *result;
  51
  52   /* Get error string.  */
  53   result = (struct dl_action_result *) __libc_getspecific (key);
  54   if (result == NULL)
  55     result = &last_result;
  56
  57   /* Test whether we already returned the string.  */
  58   if (result->returned != 0)
  59     {
  60       /* We can now free the string.  */
  61       if (result->errstring != NULL)
  62         {
  63           if (strcmp (result->errstring, "out of memory") != 0)
  64             free ((char *) result->errstring);
  65           result->errstring = NULL;
  66         }
  67     }
  68   else if (result->errstring != NULL)
  69     {
  70       buf = (char *) result->errstring;
  71       if (__asprintf (&buf, result->errcode != 0 ? "%s: %s: %s" : "%s: %s",
  72                       result->objname, _(result->errstring),
  73                       strerror (result->errcode)) != -1)
  74         {
  75           /* We don't need the error string anymore.  */
  76           if (strcmp (result->errstring, "out of memory") != 0)
  77             free ((char *) result->errstring);
  78           result->errstring = buf;
  79         }
  80
  81       /* Mark the error as returned.  */
  82       result->returned = 1;
  83     }
  84
  85   return buf;
  86 }
  87
  88 int
  89 internal_function
  90 _dlerror_run (void (*operate) (void *), void *args)
  91 {
  92   __libc_once_define (static, once);
  93   struct dl_action_result *result;
  94
  95   /* If we have not yet initialized the buffer do it now.  */
  96   __libc_once (once, init);
  97
  98   /* Get error string and number.  */
  99   if (static_buf != NULL)
 100     result = static_buf;
 101   else
 102     {
 103       /* We don't use the static buffer and so we have a key.  Use it
 104          to get the thread-specific buffer.  */
 105       result = __libc_getspecific (key);
 106       if (result == NULL)
 107         {
 108           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 109           if (result == NULL)
 110             /* We are out of memory.  Since this is no really critical
 111                situation we carry on by using the global variable.
 112                This might lead to conflicts between the threads but
 113                they soon all will have memory problems.  */
 114             result = &last_result;
 115           else
 116             /* Set the tsd.  */
 117             __libc_setspecific (key, result);
 118         }
 119     }
 120
 121   if (result->errstring != NULL)
 122     {
 123       /* Free the error string from the last failed command.  This can
 124          happen if `dlerror' was not run after an error was found.  */
 125       if (strcmp (result->errstring, "out of memory") != 0)
 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   struct dl_action_result *result = (struct dl_action_result *) mem;
 157
 158   if (result->errstring != NULL
 159       && strcmp (result->errstring, "out of memory") != 0)
 160     free ((char *) result->errstring);
 161
 162   free (mem);
 163   __libc_setspecific (key, NULL);
 164 }