diff options
Diffstat (limited to 'Python/import.c')
| -rw-r--r-- | Python/import.c | 46 |
1 files changed, 14 insertions, 32 deletions
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 ?! - - 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. + + 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. + + 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 @@ extern time_t PyOS_GetLastModificationTime(char *, FILE *); 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 |