(cherry picked from commit e9d9494d)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

When the C imp module became _imp in 6f44d66b, the initialization function should have been renamed from PyInit_imp to PyInit__imp.

As a result of 92a3c6f4, the compiler complains:

Python/import.c:2311:21: warning: comparison of integers of different signs: 'long' and 'unsigned long' [-Wsign-compare]
    if ((i + n + 1) <= PY_SSIZE_T_MAX / sizeof(struct _inittab)) {
         ~~~~~~~~~  ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This overflow is extremely unlikely to happen, but let's avoid undefined
behavior anyway.

Fix the warning:

Python/import.c: warning: comparison between signed and unsigned integer expressions
     if ((i + n + 1) <= PY_SSIZE_T_MAX / sizeof(struct _inittab)) {

Python now supports checking bytecode cache up-to-dateness with a hash of the
source contents rather than volatile source metadata. See the PEP for details.

While a fairly straightforward idea, quite a lot of code had to be modified due
to the pervasiveness of pyc implementation details in the codebase. Changes in
this commit include:

- The core changes to importlib to understand how to read, validate, and
  regenerate hash-based pycs.

- Support for generating hash-based pycs in py_compile and compileall.

- Modifications to our siphash implementation to support passing a custom
  key. We then expose it to importlib through _imp.

- Updates to all places in the interpreter, standard library, and tests that
  manually generate or parse pyc files to grok the new format.

- Support in the interpreter command line code for long options like
  --check-hash-based-pycs.

- Tests and documentation for all of the above.

PyImport_ExtendInittab() now uses PyMem_RawRealloc() rather than
PyMem_Realloc(). PyImport_ExtendInittab() can be called before
Py_Initialize() whereas only the PyMem_Raw allocator is supposed to
be used before Py_Initialize().

Add _PyImport_Fini2() to release the memory allocated by
PyImport_ExtendInittab() at exit. PyImport_ExtendInittab() now forces
the usage of the default raw allocator, to be able to release memory
in _PyImport_Fini2().

Don't export these functions anymore to be C API, only to
Py_BUILD_CORE:

* _PyExc_Fini()
* _PyImport_Fini()
* _PyGC_DumpShutdownStats()
* _PyGC_Fini()
* _PyType_Fini()
* _Py_HashRandomization_Fini()

Remove also the initstr variable, unused since the commit
e69f0df4 pushed in 2012: "bpo-13959:
Re-implement imp.find_module() in Lib/imp.py"

Add import_find_and_load() helper function.  The addition of
the importtime option has made PyImport_ImportModuleLevelObject() large
and so using a helper seems worthwhile.  It also makes it clearer that
abs_name is the only argument needed by _find_and_load().

Py_Main() now handles two more -X options:

* -X showrefcount: new _PyCoreConfig.show_ref_count field
* -X showalloccount: new _PyCoreConfig.show_alloc_count field

Parse more env vars in Py_Main():

* Add more options to _PyCoreConfig:

  * faulthandler
  * tracemalloc
  * importtime

* Move code to parse environment variables from _Py_InitializeCore()
  to Py_Main(). This change fixes a regression from Python 3.6:
  PYTHONUNBUFFERED is now read before calling pymain_init_stdio().
* _PyFaulthandler_Init() and _PyTraceMalloc_Init() now take an
  argument to decide if the module has to be enabled at startup.
* tracemalloc_start() is now responsible to check the maximum number
  of frames.

Other changes:

* Cleanup Py_Main():

  * Rename some pymain_xxx() subfunctions
  * Add pymain_run_python() subfunction

* Cleanup Py_NewInterpreter()
* _PyInterpreterState_Enable() now reports failure
* init_hash_secret() now considers pyurandom() failure as an "user
  error": don't fail with abort().
* pymain_optlist_append() and pymain_strdup() now sets err on memory
  allocation failure.

* Don't use "Python runtime" anymore to parse command line options or
  to get environment variables: pymain_init() is now a strict
  separation.
* Use an error message rather than "crashing" directly with
  Py_FatalError(). Limit the number of calls to Py_FatalError(). It
  prepares the code to handle errors more nicely later.
* Warnings options (-W, PYTHONWARNINGS) and "XOptions" (-X) are now
  only added to the sys module once Python core is properly
  initialized.
* _PyMain is now the well identified owner of some important strings
  like: warnings options, XOptions, and the "program name". The
  program name string is now properly freed at exit.
  pymain_free() is now responsible to free the "command" string.
* Rename most methods in Modules/main.c to use a "pymain_" prefix to
  avoid conflits and ease debug.
* Replace _Py_CommandLineDetails_INIT with memset(0)
* Reorder a lot of code to fix the initialization ordering. For
  example, initializing standard streams now comes before parsing
  PYTHONWARNINGS.
* Py_Main() now handles errors when adding warnings options and
  XOptions.
* Add _PyMem_GetDefaultRawAllocator() private function.
* Cleanup _PyMem_Initialize(): remove useless global constants: move
  them into _PyMem_Initialize().
* Call _PyRuntime_Initialize() as soon as possible:
  _PyRuntime_Initialize() now returns an error message on failure.
* Add _PyInitError structure and following macros:

  * _Py_INIT_OK()
  * _Py_INIT_ERR(msg)
  * _Py_INIT_USER_ERR(msg): "user" error, don't abort() in that case
  * _Py_INIT_FAILED(err)

Support PYTHONPROFILEIMPORTTIME envvar equivalent to -X importtime

* Rewrite win_perf_counter() to only use integers internally.
* Add _PyTime_MulDiv() which compute "ticks * mul / div"
  in two parts (int part and remaining) to prevent integer overflow.
* Clock frequency is checked at initialization for integer overflow.
* Enhance also pymonotonic() to reduce the precision loss on macOS
  (mach_absolute_time() clock).

time.clock() and time.perf_counter() now use again C double
internally.

Remove also _PyTime_GetWinPerfCounterWithInfo(): use
_PyTime_GetPerfCounterDoubleWithInfo() instead on Windows.

* Add _PyTime_GetPerfCounter()
* Use _PyTime_GetPerfCounter() for -X importtime

It shows show import time of each module.
It's useful for optimizing startup time.

Typical usage: python -X importtime -c 'import requests'

Importlib was instrumented with two dtrace probes to profile import timing.
Signed-off-by: Christian Heimes <christian@python.org>

The concrete PyDict_* API is used to interact with PyInterpreterState.modules in a number of places. This isn't compatible with all dict subclasses, nor with other Mapping implementations. This patch switches the concrete API usage to the corresponding abstract API calls.

We also add a PyImport_GetModule() function (and some other helpers) to reduce a bunch of code duplication.

A bunch of code currently uses PyInterpreterState.modules directly instead of PyImport_GetModuleDict(). This complicates efforts to make changes relative to sys.modules. This patch switches to using PyImport_GetModuleDict() uniformly. Also, a number of related uses of sys.modules are updated for uniformity for the same reason.

Note that this code was already reviewed and merged as part of #1638. I reverted that and am now splitting it up into more focused parts.

PR #1638, for bpo-28411, causes problems in some (very) edge cases. Until that gets sorted out, we're reverting the merge. PR #3506, a fix on top of #1638, is also getting reverted.

* group the (stateful) runtime globals into various topical structs
* consolidate the topical structs under a single top-level _PyRuntimeState struct
* add a check-c-globals.py script that helps identify runtime globals

Other globals are excluded (see globals.txt and check-c-globals.py).

* Remove Setup.config
* Always define WITH_THREAD for compatibility.

sys.modules is the one true source.

instead of failing with SystemError.

Relative import from non-package now fails with ImportError rather than
SystemError.

* Rewrite importlib _get_module_lock(): it is now responsible to hold
  the imp lock directly.
* _find_and_load() now holds the module lock to check if name is in
  sys.modules to prevent a race condition

In rare circumstances PyImport_Import() could return NULL without raising
an error.

* Doc nits for bpo-16500

* Fix more references

* bpo-6532: Make the thread id an unsigned integer.

From C API side the type of results of PyThread_start_new_thread() and
PyThread_get_thread_ident(), the id parameter of
PyThreadState_SetAsyncExc(), and the thread_id field of PyThreadState
changed from "long" to "unsigned long".

* Restore a check in thread_get_ident().

possible.  Patch is writen with Coccinelle.

Issue #28915: Replace _PyObject_CallMethodId() with
_PyObject_CallMethodIdObjArgs() in various modules when the format string was
only made of "O" formats, PyObject* arguments.

_PyObject_CallMethodIdObjArgs() avoids the creation of a temporary tuple and
doesn't have to parse a format string.

Issue #28858: The change b9c9691c72c5 introduced a regression. It seems like
_PyObject_CallArg1() uses more stack memory than
PyObject_CallFunctionObjArgs().

* PyObject_CallFunctionObjArgs(func, NULL) => _PyObject_CallNoArg(func)
* PyObject_CallFunctionObjArgs(func, arg, NULL) => _PyObject_CallArg1(func, arg)

PyObject_CallFunctionObjArgs() allocates 40 bytes on the C stack and requires
extra work to "parse" C arguments to build a C array of PyObject*.

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

This change is part of the fastcall project. The change on listsort() is
related to the issue #23507.

UTF-8 represenatation of Unicode objects.

The latter function is more readable, faster and doesn't raise exceptions.