src/dyldLibSystemGlue.c

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
   2  *
   3  * Copyright (c) 2009-2010 Apple Inc. All rights reserved.
   4  *
   5  * @APPLE_LICENSE_HEADER_START@
   6  *
   7  * This file contains Original Code and/or Modifications of Original Code
   8  * as defined in and that are subject to the Apple Public Source License
   9  * Version 2.0 (the 'License'). You may not use this file except in
  10  * compliance with the License. Please obtain a copy of the License at
  11  * http://www.opensource.apple.com/apsl/ and read it before using this
  12  * file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  19  * Please see the License for the specific language governing rights and
  20  * limitations under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24
  25 #include <Availability.h>
  26
  27 //
  28 // This is the temporary private interface between libSystem.B.dylib and dyld
  29 //
  30
  31 //
  32 // Long ago, the compiler driver added -ldylib1.o to every dylib which caused a
  33 // __DATA,__dyld section to be added every dylib.  The new LINKEDIT format no longer requires
  34 // images to have a __DATA,__dyld section.  But until libdyld.dylib and dyld update
  35 // to some sort of vtable based interface, libdyld still needs a __DATA,__dyld section.
  36 // The code below adds that section.
  37 //
  38 struct __DATA__dyld { long lazy; int (*lookup)(const char*, void**); };
  39
  40 static volatile struct __DATA__dyld  myDyldSection __attribute__ ((section ("__DATA,__dyld"))) = { 0, 0 };
  41
  42 #if __arm__ && __MAC_OS_X_VERSION_MIN_REQUIRED
  43 // <rdar://problem/8755380>
  44 // For historical reasons, gcc and llvm-gcc added -ldylib1.o to the link line of armv6
  45 // dylibs when targeting MacOSX (but not iOS).  clang cleans up that mistake, but doing
  46 // so would break the libdyld build.  Making _dyld_func_lookup weak,hidden means if
  47 // dylib1.o is used, it overrides this, otherwise this implementation is used.
  48 __attribute__((weak))
  49 #endif
  50 __attribute__((visibility("hidden")))
  51 int _dyld_func_lookup(const char* dyld_func_name, void **address)
  52 {
  53         return (*myDyldSection.lookup)(dyld_func_name, address);
  54 }
  55
  56
  57
  58