dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 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 <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <bits/libc-lock.h>
  25
  26 /* Type for storing results of dynamic loading actions.  */
  27 struct dl_action_result
  28   {
  29     int errcode;
  30     int returned;
  31     char *errstring;
  32   };
  33 static struct dl_action_result last_result;
  34 static struct dl_action_result *static_buf;
  35
  36
  37 /* This is the key for the thread specific memory.  */
  38 static __libc_key_t key;
  39
  40 /* Destructor for the thread-specific data.  */
  41 static void init (void);
  42 static void free_key_mem (void *mem);
  43
  44
  45 char *
  46 dlerror (void)
  47 {
  48   char *buf;
  49   struct dl_action_result *result;
  50
  51   /* Get error string.  */
  52   result = (struct dl_action_result *) __libc_getspecific (key);
  53   if (result == NULL)
  54     result = &last_result;
  55
  56   /* Test whether we already returned the string.  */
  57   if (result->returned != 0)
  58     {
  59       /* We can now free the string.  */
  60       if (result->errstring != NULL)
  61         {
  62           free (result->errstring);
  63           result->errstring = NULL;
  64         }
  65       buf = NULL;
  66     }
  67   else
  68     {
  69       buf = result->errstring;
  70       if (result->errcode != 0
  71           && __asprintf (&buf, "%s: %s",
  72                          result->errstring, strerror (result->errcode)) != -1)
  73         {
  74           /* We don't need the error string anymore.  */
  75           free (result->errstring);
  76           result->errstring = buf;
  77         }
  78
  79       /* Mark the error as returned.  */
  80       result->returned = 1;
  81     }
  82
  83   return buf;
  84 }
  85
  86 int
  87 internal_function
  88 _dlerror_run (void (*operate) (void *), void *args)
  89 {
  90   __libc_once_define (static, once);
  91   struct dl_action_result *result;
  92
  93   /* If we have not yet initialized the buffer do it now.  */
  94   __libc_once (once, init);
  95
  96   /* Get error string and number.  */
  97   if (static_buf != NULL)
  98     result = static_buf;
  99   else
 100     {
 101       /* We don't use the static buffer and so we have a key.  Use it
 102          to get the thread-specific buffer.  */
 103       result = __libc_getspecific (key);
 104       if (result == NULL)
 105         {
 106           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 107           if (result == NULL)
 108             /* We are out of memory.  Since this is no really critical
 109                situation we carry on by using the global variable.
 110                This might lead to conflicts between the threads but
 111                they soon all will have memory problems.  */
 112             result = &last_result;
 113           else
 114             /* Set the tsd.  */
 115             __libc_setspecific (key, result);
 116         }
 117     }
 118
 119   if (result->errstring != NULL)
 120     /* Free the error string from the last failed command.  This can
 121        happen if `dlerror' was not run after an error was found.  */
 122     free (result->errstring);
 123
 124   result->errcode = _dl_catch_error (&result->errstring, operate, args);
 125
 126   /* If no error we mark that no error string is available.  */
 127   result->returned = result->errstring == NULL;
 128
 129   return result->errstring != NULL;
 130 }
 131
 132
 133 /* Initialize buffers for results.  */
 134 static void
 135 init (void)
 136 {
 137   if (__libc_key_create (&key, free_key_mem))
 138     /* Creating the key failed.  This means something really went
 139        wrong.  In any case use a static buffer which is better than
 140        nothing.  */
 141     static_buf = &last_result;
 142 }
 143
 144
 145 /* Free the thread specific data, this is done if a thread terminates.  */
 146 static void
 147 free_key_mem (void *mem)
 148 {
 149   free (mem);
 150   __libc_setspecific (key, NULL);
 151 }