Raise OverflowError when use_single_float cannot represent a value

msgpack/_packer.pyx

@@ -27,7 +27,7 @@ cdef extern from "pack.h":
     int msgpack_pack_false(msgpack_packer* pk) except -1
     int msgpack_pack_long_long(msgpack_packer* pk, long long d) except -1
     int msgpack_pack_unsigned_long_long(msgpack_packer* pk, unsigned long long d) except -1
-    int msgpack_pack_float(msgpack_packer* pk, float d) except -1
+    int msgpack_pack_float(msgpack_packer* pk, double d) except -1
     int msgpack_pack_double(msgpack_packer* pk, double d) except -1
     int msgpack_pack_array(msgpack_packer* pk, size_t l) except -1
     int msgpack_pack_map(msgpack_packer* pk, size_t l) except -1
@@ -179,7 +179,7 @@ cdef class Packer:
                     raise OverflowError("Integer value out of range")
         elif PyFloat_CheckExact(o) if strict else PyFloat_Check(o):
             if self.use_float:
-                msgpack_pack_float(&self.pk, <float>o)
+                msgpack_pack_float(&self.pk, <double>o)
             else:
                 msgpack_pack_double(&self.pk, <double>o)
         elif PyBytesLike_CheckExact(o) if strict else PyBytesLike_Check(o):

msgpack/pack_template.h

@@ -342,15 +342,15 @@ static inline int msgpack_pack_unsigned_long_long(msgpack_packer* x, unsigned lo
  * Float
  */
 
-static inline int msgpack_pack_float(msgpack_packer* x, float d)
+static inline int msgpack_pack_float(msgpack_packer* x, double d)
 {
     unsigned char buf[5];
     buf[0] = 0xca;
 
 #if PY_VERSION_HEX >= 0x030B00A7
-    PyFloat_Pack4(d, (char *)&buf[1], 0);
+    if (PyFloat_Pack4(d, (char *)&buf[1], 0) < 0) { return -1; }
 #else
-    _PyFloat_Pack4(d, &buf[1], 0);
+    if (_PyFloat_Pack4(d, &buf[1], 0) < 0) { return -1; }
 #endif
     msgpack_pack_append_buffer(x, buf, 5);
 }

test/test_limits.py

@@ -27,6 +27,17 @@ def test_integer():
         packb(x + 1)
 
 
+def test_single_float():
+    x = 3.4028234663852886e38  # FLT_MAX
+    assert unpackb(packb(x, use_single_float=True)) == x
+    with pytest.raises(PackOverflowError):
+        packb(x * 2, use_single_float=True)
+
+    # Infinities are representable in single precision, so they must not raise.
+    for x in (float("inf"), float("-inf")):
+        assert unpackb(packb(x, use_single_float=True)) == x
+
+
 def test_array_header():
     packer = Packer()
     packer.pack_array_header(2**32 - 1)