1 files changed, 10 insertions, 0 deletions
diff --git a/Modules/_ctypes/libffi_msvc/ffi.c b/Modules/_ctypes/libffi_msvc/ffi.c
index 1d82929..91a27dc 100644
--- a/Modules/_ctypes/libffi_msvc/ffi.c
+++ b/Modules/_ctypes/libffi_msvc/ffi.c
@@ -239,6 +239,16 @@ ffi_call(/*@dependent@*/ ffi_cif *cif,
       break;
 #else
     case FFI_SYSV:
+      /* If a single argument takes more than 8 bytes,
+         then a copy is passed by reference. */
+      for (unsigned i = 0; i < cif->nargs; i++) {
+          size_t z = cif->arg_types[i]->size;
+          if (z > 8) {
+              void *temp = alloca(z);
+              memcpy(temp, avalue[i], z);
+              avalue[i] = temp;
+          }
+      }
       /*@-usedef@*/
       return ffi_call_AMD64(ffi_prep_args, &ecif, cif->bytes,
 			   cif->flags, ecif.rvalue, fn);