libgcj/9078: libffi: problems with uint8 on powerpc

[Matthias Klose]

>Number:         9078
>Category:       libgcj
>Synopsis:       libffi: problems with uint8 on powerpc
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Dec 28 03:16:02 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     David Paul BELANGER <dbelan2@CS.McGill.CA>
>Release:        3.2.1 (Debian) (Debian unstable)
>Organization:
The Debian Project
>Environment:
System: Debian GNU/Linux (unstable)
Architecture: i686
host: i386-linux
>Description:
[ Reported to the Debian BTS as report #173074.
  Please CC 173074@bugs.debian.org on replies.
  Log of report can be found at http://bugs.debian.org/173074 ]
	

[ category libgcj, as there is no explicit libffi category]

ffi_type_uint8 and other arguments shorter than one word are
not passed in correctly to the function called by ffi_call.

Also, returns values are not passed correctly.  For example, instead of
finding the returned byte value where the pointer points to, it is found
at an offset of 3 from the pointer.

This is related to the fact that the powerpc is a big endian machine and
somewhere, bytes need to be moved.

I have included code and output I get on my powerpc machine.

Thanks,
David

-----

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


unsigned char identity(unsigned char c) {
  printf("identity: %d\n", c);
  return c;
}


int main(void) {
  ffi_cif cif;
  ffi_type *args[1];
  void *values[1];
  int b;
  unsigned char result;
  int i;

  args[0] = &ffi_type_uint;
  /*
   * args[0] = &ffi_type_uint8;  - if this type is specified,
   * function always receives 0.
   */


  b = 24;
  values[0] = &b;


  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1,
		   &ffi_type_uint8, args) != FFI_OK) {
    printf("error\n");
    return 1;
  }


  ffi_call(&cif, identity, &result, values);

  printf("at result: %d\n", result);
  printf("at result + 3: %d\n", *(&result + 3));

  /*
  for (i = 0; i < sizeof(result); i++) {
    printf("byte %d = %d\n", i, *((unsigned char *) &result));
  }
  */

  return 0;
}

-----
output:

identity: 24
at result: 0
at result + 3: 24

-----


David

>How-To-Repeat:
	
>Fix:
	
>Release-Note:
>Audit-Trail:
>Unformatted: