Issue #15167 (as part of #13959): imp.get_magic() is no implemented in

brettcannon · brettcannon · commit 77b2abd09499 · 2012-07-09T16:09:00.000-04:00
Lib/imp.py.
diff --git a/Doc/c-api/import.rst b/Doc/c-api/import.rst
@@ -172,7 +172,10 @@ Importing Modules
 
    Return the magic number for Python bytecode files (a.k.a. :file:`.pyc` and
    :file:`.pyo` files).  The magic number should be present in the first four bytes
-   of the bytecode file, in little-endian byte order.
+   of the bytecode file, in little-endian byte order. Returns -1 on error.
+
+   .. versionchanged:: 3.3
+      Return value of -1 upon failure.
 
 
 .. c:function:: const char * PyImport_GetMagicTag()
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
@@ -1761,6 +1761,9 @@ Porting C code
   :c:func:`PyUnicode_FromFormat()`, your code will automatically take
   advantage of the new unicode representations.
 
+* :c:func:`PyImport_GetMagicNumber` now returns -1 upon failure.
+
+
 Building C extensions
 ---------------------
 
diff --git a/Lib/imp.py b/Lib/imp.py
@@ -10,12 +10,12 @@
                   load_dynamic, get_frozen_object, is_frozen_package,
                   init_builtin, init_frozen, is_builtin, is_frozen,
                   _fix_co_filename, extension_suffixes)
-# Could move out of _imp, but not worth the code
-from _imp import get_magic
 
+# Directly exposed by this module
 from importlib._bootstrap import new_module
 from importlib._bootstrap import cache_from_source
 
+
 from importlib import _bootstrap
 from importlib import machinery
 import os
@@ -37,6 +37,11 @@
 IMP_HOOK = 9
 
 
+def get_magic():
+    """Return the magic number for .pyc or .pyo files."""
+    return _bootstrap._MAGIC_BYTES
+
+
 def get_tag():
     """Return the magic tag for .pyc or .pyo files."""
     return sys.implementation.cache_tag
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
@@ -300,6 +300,96 @@ def _lock_unlock_module(name):
 
 # Finder/loader utility code ##################################################
 
+"""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.
+
+The magic numbers must be spaced apart at least 2 values, as the
+-U interpeter flag will cause MAGIC+1 being used. They have been
+odd numbers for some time now.
+
+There were a variety of old schemes for setting the magic number.
+The current working scheme is to increment the previous value by
+10.
+
+Starting with the adoption of PEP 3147 in Python 3.2, every bump in magic
+number also includes a new "magic tag", i.e. a human readable string used
+to represent the magic number in __pycache__ directories.  When you change
+the magic number, you must also set a new unique magic tag.  Generally this
+can be named after the Python major version of the magic number bump, but
+it can really be anything, as long as it's different than anything else
+that's come before.  The tags are included in the following table, starting
+with Python 3.2a0.
+
+Known values:
+ Python 1.5:   20121
+ Python 1.5.1: 20121
+    Python 1.5.2: 20121
+    Python 1.6:   50428
+    Python 2.0:   50823
+    Python 2.0.1: 50823
+    Python 2.1:   60202
+    Python 2.1.1: 60202
+    Python 2.1.2: 60202
+    Python 2.2:   60717
+    Python 2.3a0: 62011
+    Python 2.3a0: 62021
+    Python 2.3a0: 62011 (!)
+    Python 2.4a0: 62041
+    Python 2.4a3: 62051
+    Python 2.4b1: 62061
+    Python 2.5a0: 62071
+    Python 2.5a0: 62081 (ast-branch)
+    Python 2.5a0: 62091 (with)
+    Python 2.5a0: 62092 (changed WITH_CLEANUP opcode)
+    Python 2.5b3: 62101 (fix wrong code: for x, in ...)
+    Python 2.5b3: 62111 (fix wrong code: x += yield)
+    Python 2.5c1: 62121 (fix wrong lnotab with for loops and
+                         storing constants that should have been removed)
+    Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp)
+    Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode)
+    Python 2.6a1: 62161 (WITH_CLEANUP optimization)
+    Python 3000:   3000
+                   3010 (removed UNARY_CONVERT)
+                   3020 (added BUILD_SET)
+                   3030 (added keyword-only parameters)
+                   3040 (added signature annotations)
+                   3050 (print becomes a function)
+                   3060 (PEP 3115 metaclass syntax)
+                   3061 (string literals become unicode)
+                   3071 (PEP 3109 raise changes)
+                   3081 (PEP 3137 make __file__ and __name__ unicode)
+                   3091 (kill str8 interning)
+                   3101 (merge from 2.6a0, see 62151)
+                   3103 (__file__ points to source file)
+    Python 3.0a4: 3111 (WITH_CLEANUP optimization).
+    Python 3.0a5: 3131 (lexical exception stacking, including POP_EXCEPT)
+    Python 3.1a0: 3141 (optimize list, set and dict comprehensions:
+            change LIST_APPEND and SET_ADD, add MAP_ADD)
+    Python 3.1a0: 3151 (optimize conditional branches:
+            introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
+    Python 3.2a0: 3160 (add SETUP_WITH)
+                  tag: cpython-32
+    Python 3.2a1: 3170 (add DUP_TOP_TWO, remove DUP_TOPX and ROT_FOUR)
+                  tag: cpython-32
+    Python 3.2a2  3180 (add DELETE_DEREF)
+    Python 3.3a0  3190 __class__ super closure changed
+    Python 3.3a0  3200 (__qualname__ added)
+                     3210 (added size modulo 2**32 to the pyc header)
+    Python 3.3a1  3220 (changed PEP 380 implementation)
+    Python 3.3a4  3230 (revert changes to implicit __class__ closure)
+
+MAGIC must change whenever the bytecode emitted by the compiler may no
+longer be understood by older implementations of the eval loop (usually
+due to the addition of new opcodes).
+
+"""
+_RAW_MAGIC_NUMBER = 3230 | ord('\r') << 16 | ord('\n') << 24
+_MAGIC_BYTES = bytes(_RAW_MAGIC_NUMBER >> n & 0xff for n in range(0, 25, 8))
+
 _PYCACHE = '__pycache__'
 
 SOURCE_SUFFIXES = ['.py']  # _setup() adds .pyw as needed.
@@ -611,7 +701,7 @@ def _bytes_from_bytecode(self, fullname, data, bytecode_path, source_stats):
         magic = data[:4]
         raw_timestamp = data[4:8]
         raw_size = data[8:12]
-        if magic != _MAGIC_NUMBER:
+        if magic != _MAGIC_BYTES:
             msg = 'bad magic number in {!r}: {!r}'.format(fullname, magic)
             raise ImportError(msg, name=fullname, path=bytecode_path)
         elif len(raw_timestamp) != 4:
@@ -768,7 +858,7 @@ def get_code(self, fullname):
         _verbose_message('code object from {}', source_path)
         if (not sys.dont_write_bytecode and bytecode_path is not None and
             source_mtime is not None):
-            data = bytearray(_MAGIC_NUMBER)
+            data = bytearray(_MAGIC_BYTES)
             data.extend(_w_long(source_mtime))
             data.extend(_w_long(len(source_bytes)))
             data.extend(marshal.dumps(code_object))
@@ -1427,8 +1517,6 @@ def __import__(name, globals={}, locals={}, fromlist=[], level=0):
         return _handle_fromlist(module, fromlist, _gcd_import)
 
 
-_MAGIC_NUMBER = None  # Set in _setup()
-
 
 def _setup(sys_module, _imp_module):
     """Setup importlib by importing needed built-in modules and injecting them
@@ -1488,7 +1576,6 @@ def _setup(sys_module, _imp_module):
     setattr(self_module, 'path_separators', set(path_separators))
     # Constants
     setattr(self_module, '_relax_case', _make_relax_case())
-    setattr(self_module, '_MAGIC_NUMBER', _imp_module.get_magic())
     if builtin_os == 'nt':
         SOURCE_SUFFIXES.append('.pyw')
 
diff --git a/Python/import.c b/Python/import.c
@@ -27,97 +27,7 @@ typedef unsigned short mode_t;
 #endif
 
 
-/* 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.
-
-   The magic numbers must be spaced apart at least 2 values, as the
-   -U interpeter flag will cause MAGIC+1 being used. They have been
-   odd numbers for some time now.
-
-   There were a variety of old schemes for setting the magic number.
-   The current working scheme is to increment the previous value by
-   10.
-
-   Starting with the adoption of PEP 3147 in Python 3.2, every bump in magic
-   number also includes a new "magic tag", i.e. a human readable string used
-   to represent the magic number in __pycache__ directories.  When you change
-   the magic number, you must also set a new unique magic tag.  Generally this
-   can be named after the Python major version of the magic number bump, but
-   it can really be anything, as long as it's different than anything else
-   that's come before.  The tags are included in the following table, starting
-   with Python 3.2a0.
-
-   Known values:
-       Python 1.5:   20121
-       Python 1.5.1: 20121
-       Python 1.5.2: 20121
-       Python 1.6:   50428
-       Python 2.0:   50823
-       Python 2.0.1: 50823
-       Python 2.1:   60202
-       Python 2.1.1: 60202
-       Python 2.1.2: 60202
-       Python 2.2:   60717
-       Python 2.3a0: 62011
-       Python 2.3a0: 62021
-       Python 2.3a0: 62011 (!)
-       Python 2.4a0: 62041
-       Python 2.4a3: 62051
-       Python 2.4b1: 62061
-       Python 2.5a0: 62071
-       Python 2.5a0: 62081 (ast-branch)
-       Python 2.5a0: 62091 (with)
-       Python 2.5a0: 62092 (changed WITH_CLEANUP opcode)
-       Python 2.5b3: 62101 (fix wrong code: for x, in ...)
-       Python 2.5b3: 62111 (fix wrong code: x += yield)
-       Python 2.5c1: 62121 (fix wrong lnotab with for loops and
-                            storing constants that should have been removed)
-       Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp)
-       Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode)
-       Python 2.6a1: 62161 (WITH_CLEANUP optimization)
-       Python 3000:   3000
-                      3010 (removed UNARY_CONVERT)
-                      3020 (added BUILD_SET)
-                      3030 (added keyword-only parameters)
-                      3040 (added signature annotations)
-                      3050 (print becomes a function)
-                      3060 (PEP 3115 metaclass syntax)
-                      3061 (string literals become unicode)
-                      3071 (PEP 3109 raise changes)
-                      3081 (PEP 3137 make __file__ and __name__ unicode)
-                      3091 (kill str8 interning)
-                      3101 (merge from 2.6a0, see 62151)
-                      3103 (__file__ points to source file)
-       Python 3.0a4: 3111 (WITH_CLEANUP optimization).
-       Python 3.0a5: 3131 (lexical exception stacking, including POP_EXCEPT)
-       Python 3.1a0: 3141 (optimize list, set and dict comprehensions:
-               change LIST_APPEND and SET_ADD, add MAP_ADD)
-       Python 3.1a0: 3151 (optimize conditional branches:
-               introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
-       Python 3.2a0: 3160 (add SETUP_WITH)
-                     tag: cpython-32
-       Python 3.2a1: 3170 (add DUP_TOP_TWO, remove DUP_TOPX and ROT_FOUR)
-                     tag: cpython-32
-       Python 3.2a2  3180 (add DELETE_DEREF)
-       Python 3.3a0  3190 __class__ super closure changed
-       Python 3.3a0  3200 (__qualname__ added)
-                     3210 (added size modulo 2**32 to the pyc header)
-       Python 3.3a1  3220 (changed PEP 380 implementation)
-       Python 3.3a4  3230 (revert changes to implicit __class__ closure)
-*/
-
-/* MAGIC must change whenever the bytecode emitted by the compiler may no
-   longer be understood by older implementations of the eval loop (usually
-   due to the addition of new opcodes)
-*/
-#define MAGIC (3230 | ((long)'\r'<<16) | ((long)'\n'<<24))
 #define CACHEDIR "__pycache__"
-/* Current magic word as global. */
-static long pyc_magic = MAGIC;
 
 /* See _PyImport_FixupExtensionObject() below */
 static PyObject *extensions = NULL;
@@ -516,7 +426,12 @@ PyImport_Cleanup(void)
 long
 PyImport_GetMagicNumber(void)
 {
-    return pyc_magic;
+    PyInterpreterState *interp = PyThreadState_Get()->interp;
+    PyObject *pyc_magic = PyObject_GetAttrString(interp->importlib,
+                                                 "_RAW_MAGIC_NUMBER");
+    if (pyc_magic == NULL)
+        return -1;
+    return PyLong_AsLong(pyc_magic);
 }
 
 
@@ -1879,30 +1794,6 @@ PyImport_Import(PyObject *module_name)
     return r;
 }
 
-
-/* Module 'imp' provides Python access to the primitives used for
-   importing modules.
-*/
-
-static PyObject *
-imp_make_magic(long magic)
-{
-    char buf[4];
-
-    buf[0] = (char) ((magic >>  0) & 0xff);
-    buf[1] = (char) ((magic >>  8) & 0xff);
-    buf[2] = (char) ((magic >> 16) & 0xff);
-    buf[3] = (char) ((magic >> 24) & 0xff);
-
-    return PyBytes_FromStringAndSize(buf, 4);
-}
-
-static PyObject *
-imp_get_magic(PyObject *self, PyObject *noargs)
-{
-    return imp_make_magic(pyc_magic);
-}
-
 static PyObject *
 imp_extension_suffixes(PyObject *self, PyObject *noargs)
 {
@@ -2049,10 +1940,6 @@ imp_load_dynamic(PyObject *self, PyObject *args)
 PyDoc_STRVAR(doc_imp,
 "(Extremely) low-level import machinery bits as used by importlib and imp.");
 
-PyDoc_STRVAR(doc_get_magic,
-"get_magic() -> string\n\
-Return the magic number for .pyc or .pyo files.");
-
 PyDoc_STRVAR(doc_extension_suffixes,
 "extension_suffixes() -> list of strings\n\
 Returns the list of file suffixes used to identify extension modules.");
@@ -2075,7 +1962,6 @@ Release the interpreter's import lock.\n\
 On platforms without threads, this function does nothing.");
 
 static PyMethodDef imp_methods[] = {
-    {"get_magic",        imp_get_magic,    METH_NOARGS,  doc_get_magic},
     {"extension_suffixes", imp_extension_suffixes, METH_NOARGS,
         doc_extension_suffixes},
     {"lock_held",        imp_lock_held,    METH_NOARGS,  doc_lock_held},
diff --git a/Python/importlib.h b/Python/importlib.h
