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

Author: jonashaag

pandas/_libs/byteswap.pyx

@@ -10,13 +10,14 @@ 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):
     assert offset + 4 < len(data)
     cdef:
         const char *data_ptr = data
-        float res = (<float*>(data_ptr + offset))[0]
+        float res = (<float *>(data_ptr + offset))[0]
     if byteswap:
         res = _byteswap_float(res)
     return res
@@ -26,7 +27,7 @@ def read_double_with_byteswap(bytes data, Py_ssize_t offset, bint byteswap):
     assert offset + 8 < len(data)
     cdef:
         const char *data_ptr = data
-        double res = (<double*>(data_ptr + offset))[0]
+        double res = (<double *>(data_ptr + offset))[0]
     if byteswap:
         res = _byteswap_double(res)
     return res
@@ -82,12 +83,16 @@ cdef extern from *:
 
 
 cdef float _byteswap_float(float num):
-    cdef uint32_t *intptr = <uint32_t *>&num
-    intptr[0] = _byteswap4(intptr[0])
+    cdef uint32_t num_uint
+    memcpy(&num_uint, &num, sizeof(float))
+    num_uint = _byteswap4(num_uint)
+    memcpy(&num, &num_uint, sizeof(uint32_t))
     return num
 
 
 cdef double _byteswap_double(double num):
-    cdef uint64_t *intptr = <uint64_t *>&num
-    intptr[0] = _byteswap8(intptr[0])
+    cdef uint64_t num_uint
+    memcpy(&num_uint, &num, sizeof(double))
+    num_uint = _byteswap8(num_uint)
+    memcpy(&num, &num_uint, sizeof(uint64_t))
     return num