unix/modffi: Use a union for passing/returning FFI values.

This fixes a bug where double arguments on a 32-bit architecture would not
be passed correctly because they only had 4 bytes of storage (not 8).  It
also fixes a compiler warning/error in return_ffi_value on certian
architectures: array subscript 'double[0]' is partly outside array bounds
of 'ffi_arg[1]' {aka 'long unsigned int[1]'}.

Fixes issue #7064.

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/tests/unix/ffi_float.py b/tests/unix/ffi_float.py
index d039398965..03bd9f7f17 100644
--- a/tests/unix/ffi_float.py
+++ b/tests/unix/ffi_float.py
@@ -35,6 +35,15 @@ print("%.6f" % strtod("1.23", None))
 # test passing double and float args
 libm = ffi_open(("libm.so", "libm.so.6", "libc.so.0", "libc.so.6", "libc.dylib"))
 tgamma = libm.func("d", "tgamma", "d")
-for fun in (tgamma,):
+for fun_name in ("tgamma",):
+    fun = globals()[fun_name]
     for val in (0.5, 1, 1.0, 1.5, 4, 4.0):
-        print("%.6f" % fun(val))
+        print(fun_name, "%.5f" % fun(val))
+
+# test passing 2x float/double args
+powf = libm.func("f", "powf", "ff")
+pow = libm.func("d", "pow", "dd")
+for fun_name in ("powf", "pow"):
+    fun = globals()[fun_name]
+    for args in ((0, 1), (1, 0), (2, 0.5), (3, 4)):
+        print(fun_name, "%.5f" % fun(*args))