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* [Bug fortran/99922] New: Bind(C) with assumed length character should work
@ 2021-04-05 23:18 everythingfunctional at protonmail dot com
2021-04-06 2:04 ` [Bug fortran/99922] " kargl at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: everythingfunctional at protonmail dot com @ 2021-04-05 23:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99922
Bug ID: 99922
Summary: Bind(C) with assumed length character should work
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: everythingfunctional at protonmail dot com
Target Milestone: ---
As of (at least) Fortran 2018, bind(C) should be allowed for procedures with
assumed length character variables, as one can pass CFI_cdesc_t* from the C
side and it's supposed to work.
MWE below
! main.f90
program main
implicit none
interface
subroutine say_hello_c() bind(C)
end subroutine
end interface
call say_hello_c()
end program
! say_hello_fortran.f90
subroutine say_hello_fortran(name) bind(C)
use iso_c_binding, only: c_char
implicit none
character(len=*, kind=c_char), intent(in) :: name
print *, "Hello from Fortran, " // name // "!"
end subroutine
! say_hello_c.c
#include <string.h>
#include <ISO_Fortran_binding.h>
extern void say_hello_fortran(CFI_cdesc_t * name_descriptor);
void say_hello_c() {
char * name = "World";
CFI_cdesc_t name_descriptor;
int error_code = CFI_establish(
&name_descriptor,
name,
CFI_attribute_other,
CFI_type_char,
strlen(name),
0,
NULL);
say_hello_fortran(&name_descriptor);
}
Compiling say_hello_fortran.f90 gives the error
say_hello_fortran.f90:1:33:
1 | subroutine say_hello_fortran(name) bind(C)
| 1
Error: Character argument ‘name’ at (1) must be length 1 because procedure
‘say_hello_fortran’ is BIND(C)
But the relevant text from the standard says (from section 18.3.6):
any dummy argument without the VALUE attribute corresponds to a formal
parameter of the prototype that is of a pointer type, and either
the dummy argument is a nonallocatable nonpointer variable of type CHARACTER
with assumed character length and the formal parameter is a pointer to
CFI_cdesc_t,
So this is supposed to be allowed, and I can confirm that I can compile and
execute the above example and obtain the expected result with Intel (ifort and
icc).
output of gfortran --version:
GNU Fortran (Ubuntu 10.2.0-13ubuntu1) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug fortran/99922] Bind(C) with assumed length character should work
2021-04-05 23:18 [Bug fortran/99922] New: Bind(C) with assumed length character should work everythingfunctional at protonmail dot com
@ 2021-04-06 2:04 ` kargl at gcc dot gnu.org
2021-04-06 16:34 ` everythingfunctional at protonmail dot com
2021-10-22 20:42 ` sandra at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: kargl at gcc dot gnu.org @ 2021-04-06 2:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99922
kargl at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-04-06
Status|UNCONFIRMED |NEW
CC| |kargl at gcc dot gnu.org
Priority|P3 |P4
Ever confirmed|0 |1
--- Comment #1 from kargl at gcc dot gnu.org ---
(In reply to Brad Richardson from comment #0)
>
> So this is supposed to be allowed, and I can confirm that I can compile and
> execute the above example and obtain the expected result with Intel (ifort
> and icc).
>
What result did Intel produce?
This patch suppresses the error message, which allows the code
to compile. gfortran may produces wrong code. Someone else can
investigate that issue
diff --git a/gcc/fortran/decl.c b/gcc/fortran/decl.c
index 9039c9dca2a..b10a92ca234 100644
--- a/gcc/fortran/decl.c
+++ b/gcc/fortran/decl.c
@@ -1549,19 +1549,21 @@ gfc_verify_c_interop_param (gfc_symbol *sym)
sym->ns->proc_name->name);
}
- /* Character strings are only C interoperable if they have a
- length of 1. */
- if (sym->ts.type == BT_CHARACTER && !sym->attr.dimension)
+ /* In F2008 (and earlier?) a character string is only C
+ interoperable if it has a length of 1. With F2018, if the
+ string is a dummy argument, it can have an assumed length if
+ the formal argument is CFI_cdesc_t. */
+ if (sym->ts.type == BT_CHARACTER && !sym->attr.dimension
+ && !((gfc_option.allow_std & GFC_STD_F2018) && sym->attr.dummy))
{
gfc_charlen *cl = sym->ts.u.cl;
+
if (!cl || !cl->length || cl->length->expr_type != EXPR_CONSTANT
|| mpz_cmp_si (cl->length->value.integer, 1) != 0)
{
- gfc_error ("Character argument %qs at %L "
- "must be length 1 because "
- "procedure %qs is BIND(C)",
- sym->name, &sym->declared_at,
- sym->ns->proc_name->name);
+ gfc_error ("Character argument %qs at %L must be length 1 "
+ "because procedure %qs is BIND(C)", sym->name,
+ &sym->declared_at, sym->ns->proc_name->name);
retval = false;
}
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug fortran/99922] Bind(C) with assumed length character should work
2021-04-05 23:18 [Bug fortran/99922] New: Bind(C) with assumed length character should work everythingfunctional at protonmail dot com
2021-04-06 2:04 ` [Bug fortran/99922] " kargl at gcc dot gnu.org
@ 2021-04-06 16:34 ` everythingfunctional at protonmail dot com
2021-10-22 20:42 ` sandra at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: everythingfunctional at protonmail dot com @ 2021-04-06 16:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99922
--- Comment #2 from Brad Richardson <everythingfunctional at protonmail dot com> ---
Output from compiling and running with Intel:
[pop-os:~/tmp/c_string_interop] ifort -V
Intel(R) Fortran Intel(R) 64 Compiler Classic for applications running on
Intel(R) 64, Version 2021.2.0 Build 20210228_000000
Copyright (C) 1985-2021 Intel Corporation. All rights reserved.
[pop-os:~/tmp/c_string_interop] ifort -c say_hello_fortran.f90 -o
say_hello_fortran.f90.o
[pop-os:~/tmp/c_string_interop] icc -c say_hello_c.c -o say_hello_c.c.o
[pop-os:~/tmp/c_string_interop] ifort -c main.f90 -o main.f90.o
[pop-os:~/tmp/c_string_interop] ifort say_hello_fortran.f90.o say_hello_c.c.o
main.f90.o -o main.exe
[pop-os:~/tmp/c_string_interop] ./main.exe
Hello from Fortran, World!
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug fortran/99922] Bind(C) with assumed length character should work
2021-04-05 23:18 [Bug fortran/99922] New: Bind(C) with assumed length character should work everythingfunctional at protonmail dot com
2021-04-06 2:04 ` [Bug fortran/99922] " kargl at gcc dot gnu.org
2021-04-06 16:34 ` everythingfunctional at protonmail dot com
@ 2021-10-22 20:42 ` sandra at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: sandra at gcc dot gnu.org @ 2021-10-22 20:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99922
sandra at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sandra at gcc dot gnu.org
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #3 from sandra at gcc dot gnu.org ---
This is a duplicate of now-fixed PR 92482.
*** This bug has been marked as a duplicate of bug 92482 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-10-22 20:42 UTC | newest]
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-- links below jump to the message on this page --
2021-04-05 23:18 [Bug fortran/99922] New: Bind(C) with assumed length character should work everythingfunctional at protonmail dot com
2021-04-06 2:04 ` [Bug fortran/99922] " kargl at gcc dot gnu.org
2021-04-06 16:34 ` everythingfunctional at protonmail dot com
2021-10-22 20:42 ` sandra at gcc dot gnu.org
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