Fix pandas-dev#54391: Invalid pointer aliasing in SAS7BDAT parser

Author: jonashaag

pandas/_libs/byteswap.pyx

@@ -10,6 +10,7 @@ from libc.stdint cimport (
     uint32_t,
     uint64_t,
 )
+from libc.string cimport memcpy
 
 
 def read_float_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
@@ -82,12 +83,14 @@ cdef extern from *:
 
 
 cdef float _byteswap_float(float num):
-    cdef uint32_t *intptr = <uint32_t *>&num
-    intptr[0] = _byteswap4(intptr[0])
-    return num
+    cdef uint32_t num_uint
+    memcpy(&num_uint, &num, sizeof(float))
+    num_uint = _byteswap4(num_uint)
+    return (<float *>&num_uint)[0]
 
 
 cdef double _byteswap_double(double num):
-    cdef uint64_t *intptr = <uint64_t *>&num
-    intptr[0] = _byteswap8(intptr[0])
-    return num
+    cdef uint64_t num_uint
+    memcpy(&num_uint, &num, sizeof(double))
+    num_uint = _byteswap8(num_uint)
+    return (<double *>&num_uint)[0]