size of a derived type containing pointers...
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From: pehache-tolai on 25 Mar 2010 03:49 Hello, In my code I need to determine the size of various variables which are defined as derived types. Until now I used to use the INQUIRE() function, but it doesn't work if the derived type contains some pointers. Is there a (not too complicated) solution ? I don't need to know the size of the objects pointed or allocated by the pointers, but only the size of the derived type. Thanks, -- pehache
From: robert.corbett on 25 Mar 2010 05:58 On Mar 25, 12:49 am, pehache-tolai <pehach...(a)gmail.com> wrote: > Hello, > > In my code I need to determine the size of various variables which are > defined as derived types. > > Until now I used to use the INQUIRE() function, but it doesn't work if > the derived type contains some pointers. Is there a (not too > complicated) solution ? I don't need to know the size of the objects > pointed or allocated by the pointers, but only the size of the derived > type. > > Thanks, > > -- > pehache The easiest way would be to declare an array of two of them and subtract the LOC of the second from the LOC of the first. For example, using Oracle Solaris Fortran in 32-bit mode, the program PROGRAM MAIN TYPE T TYPE(T), POINTER :: P END TYPE TYPE(T) A(2) PRINT *, LOC(A(2)) - LOC(A(1)) END prints 4 The function LOC is a nonstandard extension, but one that is almost always present. I showed in a previous posting how to do the same thing using only standard features, but some people thought that approach was too ugly to even consider. Bob Corbett
From: pehache-tolai on 25 Mar 2010 11:25 On 25 mar, 10:58, robert.corb...(a)sun.com wrote: > > The easiest way would be to declare an array of two of them > and subtract the LOC of the second from the LOC of the first. > For example, using Oracle Solaris Fortran in 32-bit mode, the > program > > PROGRAM MAIN > TYPE T > TYPE(T), POINTER :: P > END TYPE > TYPE(T) A(2) > PRINT *, LOC(A(2)) - LOC(A(1)) > END > > prints > > 4 > > The function LOC is a nonstandard extension, but one that > is almost always present. Thanks ! Now I remember that I already seen something like that some years ago... > I showed in a previous posting > how to do the same thing using only standard features, > but some people thought that approach was too ugly to even > consider. > Probably I would have tried to equivalence a variable of the derived type with a large enough integer array, then fill the derived type with some values, then check until which element the integer array has been modified. But I guess this can fail in some cases : type my_type real :: x complex, pointer :: y(:) integer :: n end type type(my_type) :: A integer :: B(1000) ! B must be larger than A equivalence (A,B) B(:) = 0 A%x = huge(0.0) allocate( A%y(10) ) A%n = huge(0) size_of_my_type = size(B) while (B(size_of_my_type) == 0 .and. size_of_my_type > 0) size_of_my_type = size_of_my_type - 1 end while -- pehache
From: Richard Maine on 25 Mar 2010 11:59 pehache-tolai <pehache.7(a)gmail.com> wrote: > In my code I need to determine the size of various variables which are > defined as derived types. > > Until now I used to use the INQUIRE() function, but it doesn't work if > the derived type contains some pointers. Is there a (not too > complicated) solution ? I don't need to know the size of the objects > pointed or allocated by the pointers, but only the size of the derived > type. There is currently no portable standard-conforming way. Bob mentioned the LOC function, but I think he overstates when he says it is "almost always present." I haven't actually checked recently, but I doubt it is present in some of the compilers I have most used. I'd probably agree if the claim were modified to say that almost all compilers have some similar functionality, possibly under a different name. One possible variant that you will probably find in most current compilers is the f2003 C_LOC function. It does require extra trickery to convert the results of C_LOC into integers for subtraction. One way would be to do it in a short C function. The equivalence trick you mentioned involves a nonstandard equivalence that some compilers will reject. As long as you are looking at nonstandard solutions anyway, you might look at one that is at least slated to become standard. I think that storage_size is in the f2008 draft. I proposed it for f2003, as a substitute for what I considered to be anacronisms otherwise being added to f2003, but my proposal didn't make it. (F2003 added ways to find storage sizes, as long as you were working only with f77 types. I considered that an anacronism. For example, you could not even get the sizes of intrinsic types of other than default or double precision kinds). -- Richard Maine | Good judgment comes from experience; email: last name at domain . net | experience comes from bad judgment. domain: summertriangle | -- Mark Twain
From: glen herrmannsfeldt on 25 Mar 2010 14:24
robert.corbett(a)sun.com wrote: (snip) > The easiest way would be to declare an array of two of them > and subtract the LOC of the second from the LOC of the first. As I found out when I tried, though, you can't subtract C_LOC(first) from C_LOC(second). It would be nice to be able to do that. -- glen |