Re: Bug with ISO_C_BINDING on Mac OS?

[Tobias Burnus <burnus at net-b dot de>]

Am 01.06.2013 14:14, schrieb Janus Weil:
> Ok, using TYPE(c_ptr) here, too.
>
> However, when the test case is updated accordingly (see attachment), I 
> also end up with a valgrind error on Linux:

You didn't do what I proposed: You missed the VALUE for "f":

    function bzReadOpen (bzerror,f,verbosity,small,unused,nUnused) bind 
(c,NAME='BZ2_bzReadOpen')
      use, intrinsic :: ISO_C_BINDING
      integer(c_int) :: bzerror
      type(c_ptr),VALUE :: f, unused
      integer(c_int),value :: verbosity,small,nUnused
      type(c_ptr) :: bzReadOpen
    end function

Without VALUE, it sometimes showed valgrind problems / segfaulted - and 
sometimes it didn't. Ignoring that real issue that you don't access what 
you want to access ...


And in a follow-up email:

> > Ok, in fact it works (on Linux) if I remove the VALUE attribute for
> > all arguments (updated code attached). Will check if this also fixes
> > it on Mac OS ...
> Seems like it does. Thanks for the help and sorry for the noise ...

But that shouldn't work. One cannot simply add VALUE attributes at will 
- it has to match what the code expects:

For verbosity and small it expects an integer - and not a pointer to an 
int. And for "f" it expects a pointer (void * or FILE *) and not a 
pointer to a pointer (void** or FILE **). Only for "bzerror" removing 
the VALUE is fine as "integer(c_int)" matches "int *". [Actually, there 
was (correctly) never a VALUE  attribute for bzerror - thus, one cannot 
remove it ;-)] - And for trailing unused arguments, it does not really 
matter one one passes, but if one want to pass a C_NULL_PTR and an 
"int", both also need the VALUE attribute.

Tobias