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Since the MAGIC number scheme is going to break on January 1st, document

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what it is more carefully and point out some of the subtleties.
This commit is contained in:
Tim Peters 2001-11-18 04:06:29 +00:00
parent 8188e792d9
commit 36515e28ed
1 changed files with 16 additions and 4 deletions
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20
Python/import.c
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@ -30,10 +30,22 @@ extern time_t PyOS_GetLastModificationTime(char *, FILE *);
/* Change for each incompatible change */ /* Change for each incompatible change */
/* The value of CR and LF is incorporated so if you ever read or write /* 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 a .pyc file in text mode the magic number will be wrong; also, the
Apple MPW compiler swaps their values, botching string constants */ 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 /* XXX Perhaps the magic number should be frozen and a version field
added to the .pyc file header? */ added to the .pyc file header? */
/* New way to come up with the magic number: (YEAR-1995), MONTH, DAY */ /* 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).
*/
#define MAGIC (60717 | ((long)'\r'<<16) | ((long)'\n'<<24)) #define MAGIC (60717 | ((long)'\r'<<16) | ((long)'\n'<<24))
/* Magic word as global; note that _PyImport_Init() can change the /* Magic word as global; note that _PyImport_Init() can change the
@ -63,7 +75,7 @@ static const struct filedescr _PyImport_StandardFiletab[] = {
{".py", "r", PY_SOURCE}, {".py", "r", PY_SOURCE},
#ifdef MS_WIN32 #ifdef MS_WIN32
{".pyw", "r", PY_SOURCE}, {".pyw", "r", PY_SOURCE},
#endif #endif
{".pyc", "rb", PY_COMPILED}, {".pyc", "rb", PY_COMPILED},
{0, 0} {0, 0}
}; };
@ -739,7 +751,7 @@ load_source_module(char *name, char *pathname, FILE *fp)
return NULL; return NULL;
} }
#endif #endif
cpathname = make_compiled_pathname(pathname, buf, cpathname = make_compiled_pathname(pathname, buf,
(size_t)MAXPATHLEN + 1); (size_t)MAXPATHLEN + 1);
if (cpathname != NULL && if (cpathname != NULL &&
(fpc = check_compiled_module(pathname, mtime, cpathname))) { (fpc = check_compiled_module(pathname, mtime, cpathname))) {