tests/basics: Add test for creating small-ints in nan-box builds.

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

tests/basics/nanbox_smallint.py

@@ -0,0 +1,42 @@
+# Test creating small integers without heap allocation in nan-boxing mode.
+
+import micropython
+
+try:
+    # Test for nan-box build by allocating a float while heap is locked.
+    # This should pass on nan-box builds.
+    micropython.heap_lock()
+    float(123)
+    micropython.heap_unlock()
+except:
+    print("SKIP")
+    raise SystemExit
+
+# Check that nan-boxing uses 64-bit floats (eg it's not object representation C).
+if float("1e100") == float("inf"):
+    print("SKIP")
+    raise SystemExit
+
+micropython.heap_lock()
+print(int("0x80000000"))
+micropython.heap_unlock()
+
+# This is the most positive small integer.
+micropython.heap_lock()
+print(int("0x3fffffffffff"))
+micropython.heap_unlock()
+
+# This is the most negative small integer.
+micropython.heap_lock()
+print(int("-0x3fffffffffff") - 1)
+micropython.heap_unlock()
+
+x = 1
+micropython.heap_lock()
+print((x << 31) + 1)
+micropython.heap_unlock()
+
+x = 1
+micropython.heap_lock()
+print((x << 45) + 1)
+micropython.heap_unlock()

tests/basics/nanbox_smallint.py.exp

@@ -0,0 +1,5 @@
+2147483648
+70368744177663
+-70368744177664
+2147483649
+35184372088833