gh-161475: Fix ctypes structures with float arrays returned on Linux SPARC

On Linux, GCC and clang pass arrays of floating-point type in a structure
in integer registers; only Solaris follows the vendor ABI there (GCC PR
target/114416). Since gh-110190, ctypes described such array elements to
libffi as floats on all SPARC, so libffi read structures returned by value
from the FP registers on Linux.

Author: shalseth

Misc/NEWS.d/next/Library/2026-11-06-11-59-26.gh-issue-161475.82LWf4.rst

@@ -0,0 +1,2 @@
+Fix :mod:`ctypes` structures containing arrays of floating-point type
+returned by value on 64-bit Linux SPARC.

Modules/_ctypes/stgdict.c

@@ -683,10 +683,22 @@ _replace_array_elements(ctypes_state *st, PyObject *layout_fields,
             structs[struct_index].type = FFI_TYPE_STRUCT;
             structs[struct_index].elements = &dummy_types[dummy_index];
             ++struct_index;
+            ffi_type *etype = &einfo->ffi_type_pointer;
+#if defined(__sparc__) && defined(__arch64__) && !defined(__sun)
+            /* On Linux, GCC and clang pass arrays of floating-point type
+               in a structure in integer registers; only Solaris follows
+               the vendor ABI here (GCC PR target/114416). */
+            if (etype->type == FFI_TYPE_FLOAT) {
+                etype = &ffi_type_uint32;
+            }
+            else if (etype->type == FFI_TYPE_DOUBLE) {
+                etype = &ffi_type_uint64;
+            }
+#endif
             /* Copy over the element's type, length times. */
             while (length > 0) {
                 assert(dummy_index < (num_ffi_type_pointers));
-                dummy_types[dummy_index++] = &einfo->ffi_type_pointer;
+                dummy_types[dummy_index++] = etype;
                 length--;
             }
             assert(dummy_index < (num_ffi_type_pointers));