mercurial/exewrapper.c

demandimport: fix a crash in LazyFinder.__delattr__

I was tinkering with `with hgdemandimport.deactivated()` wrapped around loading
the keyring module, and got spew that seemed to be confirmed by PyCharm.  But I
can't believe we haven't seen this before (and phabricator uses the same
pattern):

    ** Unknown exception encountered with possibly-broken third-party extension "mercurial_keyring" 1.4.3 (keyring 23.11.0, backend unknown)
    ** which supports versions unknown of Mercurial.
    ** Please disable "mercurial_keyring" and try your action again.
    ** If that fixes the bug please report it to https://foss.heptapod.net/mercurial/mercurial_keyring/issues
    ** Python 3.9.15 (main, Oct 13 2022, 04:28:25) [GCC 7.5.0]
    ** Mercurial Distributed SCM (version 6.3.1)
    ** Extensions loaded: absorb, attorc 20220315, blackbox, eol, extdiff, fastannotate, lfs, mercurial_keyring 1.4.3 (keyring 23.11.0, backend unknown), phabblocker 20220315, phabricator 20220315, purge, rebase, schemes, share, show, strip, uncommit
    Traceback (most recent call last):
      File "/usr/local/bin/hg", line 59, in <module>
        dispatch.run()
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 143, in run
        status = dispatch(req)
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 232, in dispatch
        status = _rundispatch(req)
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 276, in _rundispatch
        ret = _runcatch(req) or 0
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 451, in _runcatch
        return _callcatch(ui, _runcatchfunc)
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 461, in _callcatch
        return scmutil.callcatch(ui, func)
      File "/usr/local/lib/python3.9/site-packages/mercurial/scmutil.py", line 153, in callcatch
        return func()
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 441, in _runcatchfunc
        return _dispatch(req)
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1265, in _dispatch
        return runcommand(
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 899, in runcommand
        ret = _runcommand(ui, options, cmd, d)
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1277, in _runcommand
        return cmdfunc()
      File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1263, in <lambda>
        d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
      File "/usr/local/lib/python3.9/site-packages/mercurial/util.py", line 1880, in check
        return func(*args, **kwargs)
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 962, in cmd_keyring_check
        user, pwd, source, final_url = handler.get_credentials(
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 497, in get_credentials
        keyring_pwd = password_store.get_http_password(keyring_url, actual_user)
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 287, in get_http_password
        return self._read_password_from_keyring(
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 335, in _read_password_from_keyring
        keyring = import_keyring()
>> `with hgdemandimport.deactivated()` inserted here
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 120, in import_keyring
        return _import_keyring()
      File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 133, in _import_keyring
        mod, was_imported_now = meu.direct_import_ext(
      File "/usr/lib/python3.9/site-packages/mercurial_extension_utils.py", line 1381, in direct_import_ext
        __import__(module_name)
      File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
      File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
        self.loader.exec_module(module)
      File "/usr/lib/python3.9/site-packages/keyring/__init__.py", line 1, in <module>
        from .core import (
      File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
      File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
        self.loader.exec_module(module)
      File "/usr/lib/python3.9/site-packages/keyring/core.py", line 11, in <module>
        from . import backend, credentials
      File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
      File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
        self.loader.exec_module(module)
      File "/usr/lib/python3.9/site-packages/keyring/backend.py", line 13, in <module>
        from .py312compat import metadata
      File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
      File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
        self.loader.exec_module(module)
      File "/usr/lib/python3.9/site-packages/keyring/py312compat.py", line 10, in <module>
        import importlib_metadata as metadata  # type: ignore
      File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
      File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
        self.loader.exec_module(module)
      File "/usr/lib/python3.9/site-packages/importlib_metadata/__init__.py", line 715, in <module>
        class MetadataPathFinder(NullFinder, DistributionFinder):
      File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 24, in install
        disable_stdlib_finder()
      File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 43, in disable_stdlib_finder
        del finder.find_distributions
      File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 88, in __delattr__
        return delattr(object.__getattribute__(self, "_finder"))
    TypeError: delattr expected 2 arguments, got 1

/*
 exewrapper.c - wrapper for calling a python script on Windows

 Copyright 2012 Adrian Buehlmann <[e-mail]> and others

 This software may be used and distributed according to the terms of the
 GNU General Public License version 2 or any later version.
*/

#include <Python.h>
#include <stdio.h>
#include <tchar.h>
#include <windows.h>

#include "hgpythonlib.h"

#ifdef __GNUC__
int strcat_s(char *d, size_t n, const char *s)
{
	return !strncat(d, s, n);
}
int strcpy_s(char *d, size_t n, const char *s)
{
	return !strncpy(d, s, n);
}

#define _tcscpy_s strcpy_s
#define _tcscat_s strcat_s
#define _countof(array) (sizeof(array) / sizeof(array[0]))
#endif

static TCHAR pyscript[MAX_PATH + 10];
static TCHAR pyhome[MAX_PATH + 10];
static TCHAR pydllfile[MAX_PATH + 10];

int _tmain(int argc, TCHAR *argv[])
{
	TCHAR *p;
	int ret;
	int i;
	int n;
	TCHAR **pyargv;
	WIN32_FIND_DATA fdata;
	HANDLE hfind;
	const char *err;
	HMODULE pydll;
	void(__cdecl * Py_SetPythonHome)(TCHAR * home);
	int(__cdecl * Py_Main)(int argc, TCHAR *argv[]);

#if PY_MAJOR_VERSION >= 3
	_wputenv(L"PYTHONLEGACYWINDOWSSTDIO=1");
#endif

	if (GetModuleFileName(NULL, pyscript, _countof(pyscript)) == 0) {
		err = "GetModuleFileName failed";
		goto bail;
	}

	p = _tcsrchr(pyscript, '.');
	if (p == NULL) {
		err = "malformed module filename";
		goto bail;
	}
	*p = 0; /* cut trailing ".exe" */
	_tcscpy_s(pyhome, _countof(pyhome), pyscript);

	hfind = FindFirstFile(pyscript, &fdata);
	if (hfind != INVALID_HANDLE_VALUE) {
		/* pyscript exists, close handle */
		FindClose(hfind);
	} else {
		/* file pyscript isn't there, take <pyscript>exe.py */
		_tcscat_s(pyscript, _countof(pyscript), _T("exe.py"));
	}

	pydll = NULL;

	p = _tcsrchr(pyhome, _T('\\'));
	if (p == NULL) {
		err = "can't find backslash in module filename";
		goto bail;
	}
	*p = 0; /* cut at directory */

	/* check for private Python of HackableMercurial */
	_tcscat_s(pyhome, _countof(pyhome), _T("\\hg-python"));

	hfind = FindFirstFile(pyhome, &fdata);
	if (hfind != INVALID_HANDLE_VALUE) {
		/* Path .\hg-python exists. We are probably in HackableMercurial
		scenario, so let's load python dll from this dir. */
		FindClose(hfind);
		_tcscpy_s(pydllfile, _countof(pydllfile), pyhome);
		_tcscat_s(pydllfile, _countof(pydllfile),
		          _T("\\") _T(HGPYTHONLIB) _T(".dll"));
		pydll = LoadLibrary(pydllfile);
		if (pydll == NULL) {
			err = "failed to load private Python DLL " HGPYTHONLIB
			      ".dll";
			goto bail;
		}
		Py_SetPythonHome =
		    (void *)GetProcAddress(pydll, "Py_SetPythonHome");
		if (Py_SetPythonHome == NULL) {
			err = "failed to get Py_SetPythonHome";
			goto bail;
		}
		Py_SetPythonHome(pyhome);
	}

	if (pydll == NULL) {
		pydll = LoadLibrary(_T(HGPYTHONLIB) _T(".dll"));
		if (pydll == NULL) {
			err = "failed to load Python DLL " HGPYTHONLIB ".dll";
			goto bail;
		}
	}

	Py_Main = (void *)GetProcAddress(pydll, "Py_Main");
	if (Py_Main == NULL) {
		err = "failed to get Py_Main";
		goto bail;
	}

	/*
	Only add the pyscript to the args, if it's not already there. It may
	already be there, if the script spawned a child process of itself, in
	the same way as it got called, that is, with the pyscript already in
	place. So we optionally accept the pyscript as the first argument
	(argv[1]), letting our exe taking the role of the python interpreter.
	*/
	if (argc >= 2 && _tcscmp(argv[1], pyscript) == 0) {
		/*
		pyscript is already in the args, so there is no need to copy
		the args and we can directly call the python interpreter with
		the original args.
		*/
		return Py_Main(argc, argv);
	}

	/*
	Start assembling the args for the Python interpreter call. We put the
	name of our exe (argv[0]) in the position where the python.exe
	canonically is, and insert the pyscript next.
	*/
	pyargv = malloc((argc + 5) * sizeof(TCHAR *));
	if (pyargv == NULL) {
		err = "not enough memory";
		goto bail;
	}
	n = 0;
	pyargv[n++] = argv[0];
	pyargv[n++] = pyscript;

	/* copy remaining args from the command line */
	for (i = 1; i < argc; i++)
		pyargv[n++] = argv[i];
	/* argv[argc] is guaranteed to be NULL, so we forward that guarantee */
	pyargv[n] = NULL;

	ret = Py_Main(n, pyargv); /* The Python interpreter call */

	free(pyargv);
	return ret;

bail:
	fprintf(stderr, "abort: %s\n", err);
	return 255;
}