(Most of) SF patch 601369 (Christos Georgiou): obmalloc,structmodule:

64bit, big endian (issue 2 only).

This adds a bunch of memcpy calls via a temporary variable to avoid
alignment errors.  That's needed for some platforms.

Modules/structmodule.c

@@ -1,4 +1,3 @@
-
 /* struct module -- pack values into and (out of) strings */
 
 /* New version supporting byte order, alignment and size options,
@@ -482,6 +481,14 @@ typedef struct _formatdef {
 */
 
 /* Native mode routines. ****************************************************/
+/* NOTE:
+   In all n[up]_<type> routines handling types larger than 1 byte, there is
+   *no* guarantee that the p pointer is properly aligned for each type,
+   therefore memcpy is called.  An intermediate variable is used to
+   compensate for big-endian architectures.
+   Normally both the intermediate variable and the memcpy call will be
+   skipped by C optimisation in little-endian architectures (gcc >= 2.91
+   does this). */
 
 static PyObject *
 nu_char(const char *p, const formatdef *f)
@@ -504,38 +511,49 @@ nu_ubyte(const char *p, const formatdef *f)
 static PyObject *
 nu_short(const char *p, const formatdef *f)
 {
-	return PyInt_FromLong((long) *(short *)p);
+	short x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyInt_FromLong((long)x);
 }
 
 static PyObject *
 nu_ushort(const char *p, const formatdef *f)
 {
-	return PyInt_FromLong((long) *(unsigned short *)p);
+	unsigned short x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyInt_FromLong((long)x);
 }
 
 static PyObject *
 nu_int(const char *p, const formatdef *f)
 {
-	return PyInt_FromLong((long) *(int *)p);
+	int x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyInt_FromLong((long)x);
 }
 
 static PyObject *
 nu_uint(const char *p, const formatdef *f)
 {
-	unsigned int x = *(unsigned int *)p;
+	unsigned int x;
+	memcpy((char *)&x, p, sizeof x);
 	return PyLong_FromUnsignedLong((unsigned long)x);
 }
 
 static PyObject *
 nu_long(const char *p, const formatdef *f)
 {
-	return PyInt_FromLong(*(long *)p);
+	long x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyInt_FromLong(x);
 }
 
 static PyObject *
 nu_ulong(const char *p, const formatdef *f)
 {
-	return PyLong_FromUnsignedLong(*(unsigned long *)p);
+	unsigned long x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyLong_FromUnsignedLong(x);
 }
 
 /* Native mode doesn't support q or Q unless the platform C supports
@@ -546,27 +564,26 @@ nu_ulong(const char *p, const formatdef *f)
 static PyObject *
 nu_longlong(const char *p, const formatdef *f)
 {
-	/* p may not be properly aligned */
 	LONG_LONG x;
-	memcpy(&x, p, sizeof(LONG_LONG));
+	memcpy((char *)&x, p, sizeof x);
 	return PyLong_FromLongLong(x);
 }
 
 static PyObject *
 nu_ulonglong(const char *p, const formatdef *f)
 {
-	/* p may not be properly aligned */
 	unsigned LONG_LONG x;
-	memcpy(&x, p, sizeof(unsigned LONG_LONG));
+	memcpy((char *)&x, p, sizeof x);
 	return PyLong_FromUnsignedLongLong(x);
 }
+
 #endif
 
 static PyObject *
 nu_float(const char *p, const formatdef *f)
 {
 	float x;
-	memcpy((char *)&x, p, sizeof(float));
+	memcpy((char *)&x, p, sizeof x);
 	return PyFloat_FromDouble((double)x);
 }
 
@@ -574,14 +591,16 @@ static PyObject *
 nu_double(const char *p, const formatdef *f)
 {
 	double x;
-	memcpy((char *)&x, p, sizeof(double));
+	memcpy((char *)&x, p, sizeof x);
 	return PyFloat_FromDouble(x);
 }
 
 static PyObject *
 nu_void_p(const char *p, const formatdef *f)
 {
-	return PyLong_FromVoidPtr(*(void **)p);
+	void *x;
+	memcpy((char *)&x, p, sizeof x);
+	return PyLong_FromVoidPtr(x);
 }
 
 static int
@@ -630,6 +649,7 @@ static int
 np_short(char *p, PyObject *v, const formatdef *f)
 {
 	long x;
+	short y;
 	if (get_long(v, &x) < 0)
 		return -1;
 	if (x < SHRT_MIN || x > SHRT_MAX){
@@ -638,7 +658,8 @@ np_short(char *p, PyObject *v, const formatdef *f)
 				"<=number<=" STRINGIFY(SHRT_MAX));
 		return -1;
 	}
-	* (short *)p = (short)x;
+	y = (short)x;
+	memcpy(p, (char *)&y, sizeof y);
 	return 0;
 }
 
@@ -646,6 +667,7 @@ static int
 np_ushort(char *p, PyObject *v, const formatdef *f)
 {
 	long x;
+	unsigned short y;
 	if (get_long(v, &x) < 0)
 		return -1;
 	if (x < 0 || x > USHRT_MAX){
@@ -653,7 +675,8 @@ np_ushort(char *p, PyObject *v, const formatdef *f)
 				"short format requires 0<=number<=" STRINGIFY(USHRT_MAX));
 		return -1;
 	}
-	* (unsigned short *)p = (unsigned short)x;
+	y = (unsigned short)x;
+	memcpy(p, (char *)&y, sizeof y);
 	return 0;
 }
 
@@ -661,9 +684,11 @@ static int
 np_int(char *p, PyObject *v, const formatdef *f)
 {
 	long x;
+	int y;
 	if (get_long(v, &x) < 0)
 		return -1;
-	* (int *)p = x;
+	y = (int)x;
+	memcpy(p, (char *)&y, sizeof y);
 	return 0;
 }
 
@@ -671,9 +696,11 @@ static int
 np_uint(char *p, PyObject *v, const formatdef *f)
 {
 	unsigned long x;
+	unsigned int y;
 	if (get_ulong(v, &x) < 0)
 		return -1;
-	* (unsigned int *)p = x;
+	y = (unsigned int)x;
+	memcpy(p, (char *)&y, sizeof y);
 	return 0;
 }
 
@@ -683,7 +710,7 @@ np_long(char *p, PyObject *v, const formatdef *f)
 	long x;
 	if (get_long(v, &x) < 0)
 		return -1;
-	* (long *)p = x;
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }
 
@@ -693,7 +720,7 @@ np_ulong(char *p, PyObject *v, const formatdef *f)
 	unsigned long x;
 	if (get_ulong(v, &x) < 0)
 		return -1;
-	* (unsigned long *)p = x;
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }
 
@@ -705,7 +732,7 @@ np_longlong(char *p, PyObject *v, const formatdef *f)
 	LONG_LONG x;
 	if (get_longlong(v, &x) < 0)
 		return -1;
-	memcpy(p, &x, sizeof(LONG_LONG));
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }
 
@@ -715,7 +742,7 @@ np_ulonglong(char *p, PyObject *v, const formatdef *f)
 	unsigned LONG_LONG x;
 	if (get_ulonglong(v, &x) < 0)
 		return -1;
-	memcpy(p, &x, sizeof(unsigned LONG_LONG));
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }
 #endif
@@ -729,7 +756,7 @@ np_float(char *p, PyObject *v, const formatdef *f)
 				"required argument is not a float");
 		return -1;
 	}
-	memcpy(p, (char *)&x, sizeof(float));
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }
 
@@ -757,7 +784,7 @@ np_void_p(char *p, PyObject *v, const formatdef *f)
 					"required argument is not an integer");
 		return -1;
 	}
-	*(void **)p = x;
+	memcpy(p, (char *)&x, sizeof x);
 	return 0;
 }