libgc/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.  Of course this fails if the collector is in a dynamic
  23  * library. -HB
  24  */
  25
  26 #include "private/gc_priv.h"
  27
  28 # if defined(DYNAMIC_LOADING) && (defined(GC_PTHREADS) && !defined(GC_DARWIN_THREADS)) \
  29       || defined(GC_SOLARIS_THREADS)
  30
  31 # if defined(dlopen) && !defined(GC_USE_LD_WRAP)
  32     /* To support various threads pkgs, gc.h interposes on dlopen by     */
  33     /* defining "dlopen" to be "GC_dlopen", which is implemented below.  */
  34     /* However, both GC_FirstDLOpenedLinkMap() and GC_dlopen() use the   */
  35     /* real system dlopen() in their implementation. We first remove     */
  36     /* gc.h's dlopen definition and restore it later, after GC_dlopen(). */
  37 #   undef dlopen
  38 # endif
  39
  40   /* Make sure we're not in the middle of a collection, and make        */
  41   /* sure we don't start any.   Returns previous value of GC_dont_gc.   */
  42   /* This is invoked prior to a dlopen call to avoid synchronization    */
  43   /* issues.  We can't just acquire the allocation lock, since startup  */
  44   /* code in dlopen may try to allocate.                                */
  45   /* This solution risks heap growth in the presence of many dlopen     */
  46   /* calls in either a multithreaded environment, or if the library     */
  47   /* initialization code allocates substantial amounts of GC'ed memory. */
  48   /* But I don't know of a better solution.                             */
  49   static void disable_gc_for_dlopen()
  50   {
  51     LOCK();
  52     while (GC_incremental && GC_collection_in_progress()) {
  53         GC_collect_a_little_inner(1000);
  54     }
  55     ++GC_dont_gc;
  56     UNLOCK();
  57   }
  58
  59   /* Redefine dlopen to guarantee mutual exclusion with */
  60   /* GC_register_dynamic_libraries.                     */
  61   /* Should probably happen for other operating systems, too. */
  62
  63 #include <dlfcn.h>
  64
  65 #ifdef GC_USE_LD_WRAP
  66   void * __wrap_dlopen(const char *path, int mode)
  67 #else
  68   void * GC_dlopen(path, mode)
  69   GC_CONST char * path;
  70   int mode;
  71 #endif
  72 {
  73     void * result;
  74
  75 #   ifndef USE_PROC_FOR_LIBRARIES
  76       disable_gc_for_dlopen();
  77 #   endif
  78 #   ifdef GC_USE_LD_WRAP
  79       result = (void *)__real_dlopen(path, mode);
  80 #   else
  81       result = dlopen(path, mode);
  82 #   endif
  83 #   ifndef USE_PROC_FOR_LIBRARIES
  84       GC_enable(); /* undoes disable_gc_for_dlopen */
  85 #   endif
  86     return(result);
  87 }
  88 # endif  /* GC_PTHREADS || GC_SOLARIS_THREADS ... */
  89
  90
  91