Hi Thomas,
Am 23.06.26 um 7:02 AM schrieb Thomas Koenig:
Hello Harald,
the subject already says it: we emitted the wrong C prototypes for
deferred shape and deferred length dummies of interoperable procedures.
Here we need to pass pointers to a CFI_cdesc_t structure.
There seems to be no existing testcase exercising -fc-prototypes,
unless I missed it. This one tests the output emitted by the frontend.
Thanks for finding this method! I had not come across
dg-begin-multiline-output before. PR 120220 is about lack of testing
for -fc-prototypes; we can use that for other bugs fixed in the past; we
have had some regressions due to the lack of testing.
OK for mainline / backport to 16-branch?
Yes. Thanks for the patch!
thanks for the review!
The reporter pointed out that the first version missed the case of a
scalar assumed-length character dummy. I adjusted this after verifying
via the dump-tree that code generation does the right thing.
See attached v2 of the patch, pushed as r17-1785-ge782cebd83be59 .
Harald
Best regards
Thomas
From e782cebd83be590090216ce3642318f9121991ce Mon Sep 17 00:00:00 2001
From: Harald Anlauf <[email protected]>
Date: Mon, 22 Jun 2026 22:07:43 +0200
Subject: [PATCH] Fortran: -fc-prototypes, deferred shape and deferred length
dummies [PR125902]
PR fortran/125902
gcc/fortran/ChangeLog:
* dump-parse-tree.cc (get_c_type_name): Use CFI_cdesc_t also for
deferred shape and deferred length dummies, as well as for
assumed-length scalar character dummies.
gcc/testsuite/ChangeLog:
* gfortran.dg/c-prototypes_1.F90: New test.
---
gcc/fortran/dump-parse-tree.cc | 6 +-
gcc/testsuite/gfortran.dg/c-prototypes_1.F90 | 61 ++++++++++++++++++++
2 files changed, 66 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gfortran.dg/c-prototypes_1.F90
diff --git a/gcc/fortran/dump-parse-tree.cc b/gcc/fortran/dump-parse-tree.cc
index b2bb7fc2269..3275af3f3ec 100644
--- a/gcc/fortran/dump-parse-tree.cc
+++ b/gcc/fortran/dump-parse-tree.cc
@@ -4357,7 +4357,11 @@ get_c_type_name (gfc_typespec *ts, gfc_array_spec *as, const char **pre,
*post = "";
*type_name = "<error>";
- if (as && (as->type == AS_ASSUMED_RANK || as->type == AS_ASSUMED_SHAPE))
+ if ((as && (as->type == AS_ASSUMED_RANK
+ || as->type == AS_ASSUMED_SHAPE
+ || as->type == AS_DEFERRED))
+ || (ts->type == BT_CHARACTER
+ && (ts->deferred || ts->u.cl->length == NULL)))
{
*asterisk = true;
*post = "";
diff --git a/gcc/testsuite/gfortran.dg/c-prototypes_1.F90 b/gcc/testsuite/gfortran.dg/c-prototypes_1.F90
new file mode 100644
index 00000000000..8c54f8e7617
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/c-prototypes_1.F90
@@ -0,0 +1,61 @@
+! { dg-do compile }
+! { dg-options "-fc-prototypes" }
+!
+! PR fortran/125902
+!
+! Test -fc-prototypes for deferred shape and deferred length dummies
+
+module test_c_prototypes_module
+
+ use iso_c_binding
+ implicit none (type, external)
+
+ interface
+ subroutine testsub1(b, c, d, r, ier) bind(C)
+ import
+ character(kind=c_char,len=*), intent(in) :: b
+ real(c_float), dimension(:), intent(inout) :: c
+ real(c_double), dimension(:), allocatable, intent(inout) :: d
+ character(kind=c_char,len=:), allocatable, intent(inout) :: r
+ integer(c_int), intent(out) :: ier
+ end subroutine testsub1
+ end interface
+
+ interface
+ subroutine testsub2(b, msg, c, d, r) bind(C)
+ import
+ character(kind=c_char), intent(in) :: b(:)
+ character(kind=c_char), intent(out) :: msg(*)
+ real(c_float), dimension(*), intent(inout) :: c
+ real(c_double), dimension(:), pointer, intent(inout) :: d
+ character(kind=c_char,len=:), pointer, intent(inout) :: r
+ end subroutine testsub2
+ end interface
+
+end module test_c_prototypes_module
+
+#if 0
+!{ dg-begin-multiline-output "" }
+#include <stddef.h>
+#ifdef __cplusplus
+#include <complex>
+#define __GFORTRAN_FLOAT_COMPLEX std::complex<float>
+#define __GFORTRAN_DOUBLE_COMPLEX std::complex<double>
+#define __GFORTRAN_LONG_DOUBLE_COMPLEX std::complex<long double>
+extern "C" {
+#else
+#define __GFORTRAN_FLOAT_COMPLEX float _Complex
+#define __GFORTRAN_DOUBLE_COMPLEX double _Complex
+#define __GFORTRAN_LONG_DOUBLE_COMPLEX long double _Complex
+#endif
+
+#include <ISO_Fortran_binding.h>
+
+void testsub1 (const CFI_cdesc_t *b, CFI_cdesc_t *c, CFI_cdesc_t *d, CFI_cdesc_t *r, int *ier);
+void testsub2 (const CFI_cdesc_t *b, char *msg, float *c, CFI_cdesc_t *d, CFI_cdesc_t *r);
+
+#ifdef __cplusplus
+}
+#endif
+!{ dg-end-multiline-output "" }
+#endif
--
2.51.0
