[gcc r16-9166] Fortran: -fc-prototypes, deferred shape and deferred length dummies [PR125902]

[Harald Anlauf]

https://gcc.gnu.org/g:38de4e0a8201fdfbda604e447f4b47f2ea9c069c

commit r16-9166-g38de4e0a8201fdfbda604e447f4b47f2ea9c069c
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Mon Jun 22 22:07:43 2026 +0200

    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.
    
    (cherry picked from commit e782cebd83be590090216ce3642318f9121991ce)

Diff:
---
 gcc/fortran/dump-parse-tree.cc               |  6 ++-
 gcc/testsuite/gfortran.dg/c-prototypes_1.F90 | 61 ++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/dump-parse-tree.cc b/gcc/fortran/dump-parse-tree.cc
index bb54e646f1fc..4f494e20886f 100644
--- a/gcc/fortran/dump-parse-tree.cc
+++ b/gcc/fortran/dump-parse-tree.cc
@@ -4286,7 +4286,11 @@ 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 000000000000..8c54f8e7617a
--- /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