boehm-gc/gc_dlopen.c

   1 /*
   2  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   3  * Copyright (c) 1997 by Silicon Graphics.  All rights reserved.
   4  * Copyright (c) 2000 by Hewlett-Packard Company.  All rights reserved.
   5  *
   6  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   7  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   8  *
   9  * Permission is hereby granted to use or copy this program
  10  * for any purpose,  provided the above notices are retained on all copies.
  11  * Permission to modify the code and to distribute modified code is granted,
  12  * provided the above notices are retained, and a notice that the code was
  13  * modified is included with the above copyright notice.
  14  *
  15  * Original author: Bill Janssen
  16  * Heavily modified by Hans Boehm and others
  17  */
  18
  19 /*
  20  * This used to be in dyn_load.c.  It was extracted into a separate file
  21  * to avoid having to link against libdl.{a,so} if the client doesn't call
  22  * dlopen.  -HB
  23  */
  24
  25 #include "private/gc_priv.h"
  26
  27 # if defined(GC_PTHREADS) || defined(GC_SOLARIS_THREADS)
  28
  29 # if defined(dlopen) && !defined(GC_USE_LD_WRAP)
  30     /* To support various threads pkgs, gc.h interposes on dlopen by     */
  31     /* defining "dlopen" to be "GC_dlopen", which is implemented below.  */
  32     /* However, both GC_FirstDLOpenedLinkMap() and GC_dlopen() use the   */
  33     /* real system dlopen() in their implementation. We first remove     */
  34     /* gc.h's dlopen definition and restore it later, after GC_dlopen(). */
  35 #   undef dlopen
  36 # endif
  37
  38   /* Make sure we're not in the middle of a collection, and make        */
  39   /* sure we don't start any.   Returns previous value of GC_dont_gc.   */
  40   /* This is invoked prior to a dlopen call to avoid synchronization    */
  41   /* issues.  We can't just acquire the allocation lock, since startup  */
  42   /* code in dlopen may try to allocate.                                */
  43   /* This solution risks heap growth in the presence of many dlopen     */
  44   /* calls in either a multithreaded environment, or if the library     */
  45   /* initialization code allocates substantial amounts of GC'ed memory. */
  46   /* But I don't know of a better solution.                             */
  47   /* This can still deadlock if the client explicitly starts a GC       */
  48   /* during the dlopen.  He shouldn't do that.                          */
  49   static GC_bool disable_gc_for_dlopen()
  50   {
  51     GC_bool result;
  52     LOCK();
  53     result = GC_dont_gc;
  54     while (GC_incremental && GC_collection_in_progress()) {
  55         GC_collect_a_little_inner(1000);
  56     }
  57     GC_dont_gc = TRUE;
  58     UNLOCK();
  59     return(result);
  60   }
  61
  62   /* Redefine dlopen to guarantee mutual exclusion with */
  63   /* GC_register_dynamic_libraries.                     */
  64   /* Should probably happen for other operating systems, too. */
  65
  66 #include <dlfcn.h>
  67
  68 #ifdef GC_USE_LD_WRAP
  69   void * __wrap_dlopen(const char *path, int mode)
  70 #else
  71   void * GC_dlopen(path, mode)
  72   GC_CONST char * path;
  73   int mode;
  74 #endif
  75 {
  76     void * result;
  77     GC_bool dont_gc_save;
  78
  79 #   ifndef USE_PROC_FOR_LIBRARIES
  80       dont_gc_save = disable_gc_for_dlopen();
  81 #   endif
  82 #   ifdef GC_USE_LD_WRAP
  83       result = (void *)__real_dlopen(path, mode);
  84 #   else
  85       result = dlopen(path, mode);
  86 #   endif
  87 #   ifndef USE_PROC_FOR_LIBRARIES
  88       GC_dont_gc = dont_gc_save;
  89 #   endif
  90     return(result);
  91 }
  92 # endif  /* GC_PTHREADS || GC_SOLARIS_THREADS ... */
  93
  94
  95