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Re: is there anything unstandard in the c part here

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On 08/01/2011 07:27 AM, Ben Bacarisse wrote:
> Uno<Uno@example.invalid>  writes:
>
>> On 07/30/2011 05:23 AM, Ben Bacarisse wrote:
>>
>>> It's almost always the calling function that determines how you must
>>> interface with the called language.  This applies to best practice as
>>> much as it does to those things that are required.
>
> I made a mistake.  I meant to say "the calling language" not "the
> calling function".  The point being you need to ask Fortran people about
> the best practice.

They either don't know or don't want to share.
>
>> Ok.  Fortran is expecting a c-style pointer to a char.  This little
>> snippet gives you a feel for it.  This is pretty-new syntax, and what
>> makes it relevant to c is that fortran said *all* interop is with ISO
>> C.
>
> The C has been discussed and you've decided not to use ISO C for some
> reason so what more is there to say here?  To get an answer to your
> question about best practice you need to ask Fortran people, not C
> people.  Make sure you tell them what you are trying to do because the
> Fortran code you have looks wrong to me.

How do you figure that I'm not using iso C?  Is this a criticism of the 
fortran part, the C part, or the lack of critical distinction between 
the two?
>
>> type(c_ptr):: pa
>> end function testc
>> end interface
>> type(c_ptr), target :: pa
>> character(1, c_char),pointer::fpa(:)
>> pa = testc()
>>
>> ...
>>
>> Yes the horror of not seeing semicolons, but again I put the fortran
>> stuff at the top, so it can disappear with a reasonable edit.
>>
>> On the C side, I think I've got something that works well, but I don't
>> know that without some code review.  This is what dinkumware has for
>> strncpy; does anyone have a mnemonic for what the 'n' might mean?
>
> What do you mean "might mean"?  You know what it means because you quote
> the documentation:

N: null, not null, not null newline....
>
>> strncpy
>>
>> char *strncpy(char *restrict s1, const char *restrict s2, size_t n);
>>
>> The function copies the string s2, not including its terminating null
>> character, to successive elements of the array of char whose first
>> element has the address s1. It copies no more than n characters from
>> s2. The function then stores zero or more null characters in the next
>> elements to be altered in s1 until it stores a total of n
>> characters. It returns s1.
>>
>> So I want a char * before i get to this statement, and that leaves the
>> malloc:
>>
>> char *p = malloc(sz);
>
> There are other ways to get a char *.  You can use static storage or you
> can have the pointer to some storage passed in.  You could even be
> passed a pointer to a pointer that you assign from the C function.
> Which is considered best practice is something that the Fortran people
> can advice you about.
>
>> The reason that I might put it on the left is that I haven't been
>> handed anything that's broken, and if it doesn't draw warnings, then C
>> might be just fine this.
>>
>> Another version might be:
>>
>> char *p = (char *)malloc(sz);
>> , and I'm naive enough not to see anything wrong there,
>> technically. But as I'm sitting here, it looks like an unnecessary
>> cast.
>
> Yes, it's unnecessary.

Ok.
>
>> $ gcc -c -Wall -Wextra cfunc6.c -o cfunc.o
>> $ gfortran -c  -Wall -Wextra caller2.f03 -o caller.o
>> $ gfortran -Wall -Wextra caller.o testc.o -o out
>> $ ./out
>>   this sentence is less than fifty bytes.
>
> This can't be the output of the program you show below.  For one thing,
> the C has a syntax error and for another there's an extra '.' here.
> You've told me that despite appearances, the commands you show do
> actually use cfunc.o but I am beginning to doubt that.  Where does the
> '.' come from.
>
> When the C syntax error is fixed you still don't get what I think you
> want:
>
> $ /out | cat -A
>   this sentence is less than fifty bytes^@^@^@^@^@^@^@^@^@^@^@^@$
>
> The Fortran people can help you fix that (unless you do want this
> odd behaviour).
>
> <snip>
>> char *
>> testc (void)
>> {
>>     size_t size = 50;
>>     char *p = malloc_or_bust (size);
>>     strncpy (p, "this sentence is less than fifty bytes", size - 1);
>>     p[size - 1] = '\0
>
> '; is missing here.
>
>>     return p;
>> }
>


I don't know how I missed on all of that.

$  gcc -c -Wall -Wextra cfunc7.c -o cfunc.o
$ gfortran -c  -Wall -Wextra caller3.f03 -o caller.o
$ gfortran -Wall -Wextra caller.o cfunc.o -o out
$ ./out
  this sentence is less than fifty bytes
$ cat caller3.f03
program test
use iso_c_binding
implicit none
interface
function testc() bind(c) result(pa)
use iso_c_binding
type(c_ptr):: pa
end function testc
end interface
type(c_ptr), target :: pa
character(1, c_char),pointer::fpa(:)
pa = testc()
call c_f_pointer(pa, fpa, [50])
print*, fpa(1:50)
end program test
! gfortran -c  -Wall -Wextra caller3.f03 -o caller.o
! gfortran -Wall -Wextra caller.o cfunc.o -o out
$ cat cfunc7.c
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
char *
malloc_or_bust (size_t sz)
{
    char *p = malloc (sz);
    if (p == NULL)
      {
	fprintf (stderr, "malloc failed.\n");
	exit (EXIT_FAILURE);
      }
    return p;
}
char *
testc (void)
{
    size_t size = 50;
    char *p = malloc_or_bust (size);
    strncpy (p, "this sentence is less than fifty bytes", size - 1);
    p[size - 1] = '\0';
    return p;
}
// gcc -c -Wall -Wextra cfunc7.c -o cfunc.o
$

It might throw C people off to see the initial space of list-directed 
fortran output, like it did me.  Without a format specifier, fortran 
generates the space for historic reasons.
-- 
Uno

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is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-25 17:45 -0600
  Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-25 23:53 +0000
    Re: is there anything unstandard in the c part here gwowen <gwowen@gmail.com> - 2011-07-26 01:50 -0700
      Re: is there anything unstandard in the c part here tom st denis <tom@iahu.ca> - 2011-07-26 06:17 -0700
        Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 11:08 -0400
          Re: is there anything unstandard in the c part here tom st denis <tom@iahu.ca> - 2011-07-26 10:51 -0700
            Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:08 -0700
              Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:41 -0400
                Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 10:58 +0000
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 13:58 +0100
            Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:24 -0400
              Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 11:07 +0000
                Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:02 -0400
                Re: is there anything unstandard in the c part here Roberto Waltman <usenet@rwaltman.com> - 2011-07-28 17:16 -0400
      Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-26 09:39 -0400
        Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-07-27 07:24 +0100
          Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 07:11 -0400
          Re: is there anything unstandard in the c part here Noob <root@127.0.0.1> - 2011-07-27 15:20 +0200
          Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-27 14:25 +0000
            Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 08:10 -0700
              Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-27 17:42 +0000
                Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 12:02 -0700
                Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:04 -0700
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 22:35 -0400
          Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:34 -0400
            Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 02:13 +0100
              Re: is there anything unstandard in the c part here Ike Naar <ike@sverige.freeshell.org> - 2011-07-28 07:33 +0000
                Re: is there anything unstandard in the c part here Willem <willem@toad.stack.nl> - 2011-07-28 07:58 +0000
                Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 04:25 -0400
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 12:26 +0100
            Re: is there anything unstandard in the c part here gwowen <gwowen@gmail.com> - 2011-07-28 04:24 -0700
              Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 11:36 +0000
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 15:11 +0100
                Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 14:50 +0000
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 17:28 +0100
                Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-28 10:38 -0600
                Re: is there anything unstandard in the c part here Michael Press <rubrum@pacbell.net> - 2011-08-02 17:20 -0700
                Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-08-02 23:26 -0600
                Re: is there anything unstandard in the c part here Michael Press <rubrum@pacbell.net> - 2011-08-03 16:09 -0700
                Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:22 -0400
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 22:22 -0400
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 04:17 +0100
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 23:40 -0400
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 13:52 +0100
                Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-07-31 09:19 +0100
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-31 09:49 -0400
                Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-02 06:56 +0100
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-02 06:53 -0400
              Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 07:36 -0400
              Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:16 -0400
      Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-26 14:58 +0000
        Re: is there anything unstandard in the c part here Paul N <gw7rib@aol.com> - 2011-07-26 14:56 -0700
          Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:13 -0700
          Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 07:28 -0400
            Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 04:44 -0700
            Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 08:24 -0700
              Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 22:41 -0400
                Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:19 -0700
              Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:06 -0700
              Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 01:54 -0600
      Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 11:01 -0400
        Re: is there anything unstandard in the c part here Chad <cdalten@gmail.com> - 2011-07-26 09:49 -0700
          Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 13:18 -0400
          Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-26 17:44 +0000
          Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 17:45 +0000
          Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
            Re: is there anything unstandard in the c part here Bill Waddington <william.waddington@beezmo.com> - 2011-07-26 11:55 -0700
              Re: is there anything unstandard in the c part here lawrence.jones@siemens.com - 2011-07-26 18:11 -0400
                Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-27 20:58 -0600
            Re: is there anything unstandard in the c part here arnuld <sunrise@invalid.address> - 2011-08-02 05:24 +0000
              Re: is there anything unstandard in the c part here Ian Collins <ian-news@hotmail.com> - 2011-08-02 18:10 +1200
              Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-02 00:03 -0700
              Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-02 06:59 -0400
              Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-08-02 16:06 +0000
      Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
      Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:06 -0700
        Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-02 06:58 +0100
          Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-02 00:01 -0700
            Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-05 06:22 +0100
              Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-04 23:54 -0700
              Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-05 07:37 -0400
                Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:05 +0100
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-13 08:26 -0400
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 14:09 +0100
          Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-08-02 12:58 -0400
            Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-08-10 01:31 -0700
              Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-10 08:28 -0400
                Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:14 +0100
                Re: is there anything unstandard in the c part here "io_x" <a@b.c.invalid> - 2011-08-13 10:08 +0200
                Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-13 08:35 -0400
                Re: is there anything unstandard in the c part here "J. J. Farrell" <jjf@bcs.org.uk> - 2011-08-14 04:00 +0100
                Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-08-15 14:43 -0400
          Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-08-10 01:34 -0700
            Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:16 +0100
  Re: is there anything unstandard in the c part here Barry Schwarz <schwarzb@dqel.com> - 2011-07-25 17:52 -0700
    Re: is there anything unstandard in the c part here "J. J. Farrell" <jjf@bcs.org.uk> - 2011-07-26 02:10 +0100
    Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 06:17 +0000
      Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 00:03 -0700
        Re: is there anything unstandard in the c part here "Kleuskes & Moos" <kleuske@xs4all.nl> - 2011-07-26 00:08 -0700
        Re: is there anything unstandard in the c part here Ian Collins <ian-news@hotmail.com> - 2011-07-26 19:43 +1200
        Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 07:56 +0000
          Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 04:50 -0700
            Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 12:03 +0000
            Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
            Re: is there anything unstandard in the c part here Nobody <nobody@nowhere.com> - 2011-07-27 19:10 +0100
        Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 11:53 +0000
  Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 00:07 -0700
    Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-26 06:29 -0400
      Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-27 21:32 -0600
        Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 12:19 +0100
          Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 20:25 -0400
            Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-28 18:38 -0600
              Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 21:05 -0400
          Re: is there anything unstandard in the c part here "Morris Keesan" <mkeesan@post.harvard.edu> - 2011-07-29 14:16 -0400
            Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 20:27 +0100
            Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 01:10 -0600
          Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 00:56 -0600
            Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-30 12:23 +0100
              Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 00:01 -0600
                Re: is there anything unstandard in the c part here Ike Naar <ike@sverige.freeshell.org> - 2011-08-01 07:50 +0000
                Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 07:43 -0600
                Re: is there anything unstandard in the c part here Ike Naar <ike@sdf.lonestar.org> - 2011-08-01 15:20 +0000
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-01 14:27 +0100
                Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 08:02 -0600
                Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-01 15:42 +0100

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