proggen.org

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#include <stdio.h>
#include <ffi.h>

int main()
{
  ffi_cif cif;
  ffi_type *args[1];
  void *values[1];
  char const *s;
  int rc;
  
  typedef void (*func)( void );                       // hinzugefügt
  
  /* Initialize the argument info vectors */    
  args[0]   = &ffi_type_pointer;
  values[0] = &s;
  
  func funcptr = reinterpret_cast< func >( puts );          //hinzugefügt
  
  /* Initialize the cif */
  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1, 
                   &ffi_type_uint, args) == FFI_OK)
    {
      s = "Hello World!";
      ffi_call(&cif, funcptr, &rc, values);                 // puts nach funcptr getauscht
      /* rc now holds the result of the call to puts */
      
      printf( "rc: %d\n", rc );
      
      /* values holds a pointer to the function's arg, so to 
         call puts() again all we need to do is change the 
         value of s */
//      s = "This is cool!";
      ffi_call(&cif, funcptr, &rc, values);                 // puts  nach funcptr getauscht
      printf( "rc: %d\n", rc );
    }
  
  return 0;
}

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xin@trinity:~/xsd/try/ffi_ubuntu$ valgrind ./a.out 
==6316== Memcheck, a memory error detector
==6316== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==6316== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==6316== Command: ./a.out
==6316== 
Hello World!
rc: 13
==6316== Invalid read of size 8
==6316==    at 0x4E374A2: ffi_call (in /usr/lib/x86_64-linux-gnu/libffi.so.6.0.0)
==6316==    by 0x4009A2: main (in /home/xin/xsd/try/ffi_ubuntu/a.out)
==6316==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==6316== 
...

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xin@trinity:~/xsd/try/ffi_ubuntu$ uname -a
Linux trinity 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

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 int rc;

Code: Alles auswählen

#include <stdio.h>
#include <ffi.h>

void show( ffi_cif const & cif )
{
    printf( "abi %x\n", cif.abi);
    printf( "nargs %x\n", cif.nargs);
    printf( "bytes %x\n", cif.bytes);
    printf( "flags %x\n", cif.flags);
#ifdef FFI_EXTRA_CIF_FIELDS
    printf( "extra fields\n");
#endif
}


int main()
{
  ffi_cif cif;
  ffi_type *args[1];
  void *values[1];
  char const *s;
  ffi_arg rc;
  
  typedef void (*func)( void );
  
  /* Initialize the argument info vectors */    
  args[0]   = &ffi_type_pointer;
  values[0] = &s;
  
  func funcptr = reinterpret_cast< func >( puts );
  /*
typedef struct {
  ffi_abi abi;
  unsigned nargs;
  ffi_type **arg_types;
  ffi_type *rtype;
  unsigned bytes;
  unsigned flags;
#ifdef FFI_EXTRA_CIF_FIELDS
  FFI_EXTRA_CIF_FIELDS;
#endif
} ffi_cif;
*/
  /* Initialize the cif */
  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1, 
                   &ffi_type_uint, args) == FFI_OK)
    {
      s = "Hello World!";
      ffi_call(&cif, funcptr, &rc, values);
      /* rc now holds the result of the call to puts */
      
      printf( "rc: %d\n", rc );
      
      /* values holds a pointer to the function's arg, so to 
         call puts() again all we need to do is change the 
         value of s */
    printf( "2.\n" );
      s = "This is cool!";

      ffi_call(&cif, funcptr, &rc, values);
      printf( "rc: %d\n", rc );
    }
  
  return 0;
}