Bump the magic number to avoid sharing bytecode between 2.3 and 2.4.
Revise the long comment that explained details of the magic number
in gory detail.
diff --git a/Python/import.c b/Python/import.c
index 71ee6c3..5143a60 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -19,39 +19,20 @@
extern time_t PyOS_GetLastModificationTime(char *, FILE *);
/* In getmtime.c */
-/* Magic word to reject .pyc files generated by other Python versions */
-/* Change for each incompatible change */
-/* The value of CR and LF is incorporated so if you ever read or write
+/* Magic word to reject .pyc files generated by other Python versions.
+ It should change for each incompatible change to the bytecode.
+
+ The value of CR and LF is incorporated so if you ever read or write
a .pyc file in text mode the magic number will be wrong; also, the
Apple MPW compiler swaps their values, botching string constants.
- XXX That probably isn't important anymore.
-*/
-/* XXX Perhaps the magic number should be frozen and a version field
- added to the .pyc file header? */
-/* New way to come up with the low 16 bits of the magic number:
- (YEAR-1995) * 10000 + MONTH * 100 + DAY
- where MONTH and DAY are 1-based.
- XXX Whatever the "old way" may have been isn't documented.
- XXX This scheme breaks in 2002, as (2002-1995)*10000 = 70000 doesn't
- fit in 16 bits.
- XXX Later, sometimes 1 gets added to MAGIC in order to record that
- the Unicode -U option is in use. IMO (Tim's), that's a Bad Idea
- (quite apart from that the -U option doesn't work so isn't used
- anyway).
- XXX MAL, 2002-02-07: I had to modify the MAGIC due to a fix of the
- UTF-8 encoder (it previously produced invalid UTF-8 for unpaired
- high surrogates), so I simply bumped the month value to 20 (invalid
- month) and set the day to 1. This should be recognizable by any
- algorithm relying on the above scheme. Perhaps we should simply
- start counting in increments of 10 from now on ?!
+ Apparently, there was a distinction made between even and odd
+ bytecodes that is related to Unicode. The details aren't clear,
+ but the magic number has been odd for a long time.
- MWH, 2002-08-03: Removed SET_LINENO. Couldn't be bothered figuring
- out the MAGIC schemes, so just incremented it by 10.
-
- GvR, 2002-08-31: Because MWH changed the bytecode again, moved the
- magic number *back* to 62011. This should get the snake-farm to
- throw away its old .pyc files, amongst others.
+ There were a variety of old schemes for setting the magic number.
+ The current working scheme is to increment the previous value by
+ 10.
Known values:
Python 1.5: 20121
@@ -66,8 +47,9 @@
Python 2.3a0: 62011
Python 2.3a0: 62021
Python 2.3a0: 62011 (!)
+ Python 2.4a0: 62031
*/
-#define MAGIC (62011 | ((long)'\r'<<16) | ((long)'\n'<<24))
+#define MAGIC (62031 | ((long)'\r'<<16) | ((long)'\n'<<24))
/* Magic word as global; note that _PyImport_Init() can change the
value of this global to accommodate for alterations of how the