dlsym question

9 Apr 2011

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Hi

I have this problem with dlsym locating a symbol. It works in x86_64 but fails in i386:

#include <dlfcn.h>
#include <stdio.h>

int   main( int argc, char *argv[])
{
   void   *handle;
   void   *sym;
   int    step;

   handle = dlopen( "/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation", RTLD_LAZY);

   step = 0;
   sym = dlsym( handle, "_OBJC_CLASS_$_NSThread");
   if( ! sym)
   {
      ++step;
      sym = dlsym( handle, "OBJC_CLASS_$_NSThread");
      if( ! sym)
      {
         ++step;
         sym = dlsym( handle, ".objc_class_name_NSThread");
      }
   }
   printf( "@%d %p:%p\n", step, handle, sym);

   return( 0);
}

Output in x86_64: @1 0x7fff5fc43d78:0x7fff709366d8
Output in i386  : @2 0x8fe467a8:0x0

If I look at the output of nm

$ nm  Foundation.i386 | egrep '[oO][bB][jJ][cC].*NSThread$'
0028b3a4 S .objc_class_name_NSThread

$ nm  Foundation.x86_64 | egrep '[oO][bB][jJ][cC].*NSThread$'
00000000002a76d8 S _OBJC_CLASS_$_NSThread

I speculate that the problem is, that in i386 the symbol starts with a "." instead of an underscore and that the possibly naive dlsym code gets confused by this.

Is there a simple workaround ? (removing the leading '.' doesn't work)

Ciao
   Nat!
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