dlfcn/dlerror.c

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