mercurial/exewrapper.c

errors: catch urllib errors specifically instead of using safehasattr()

Before this patch, we would catch `IOError` and `OSError` and check if
the instance had a `.code` member (indicates `HTTPError`) or a
`.reason` member (indicates the more generic `URLError`). It seems to
me that can simply catch those exception specifically instead, so
that's what this code does. The existing code is from fbe8834923c5
(commands: report http exceptions nicely, 2005-06-17), so I suspect
it's just that there was no `urllib2` (where `URLError` lives) back
then.

The old code mentioned `SSLError` in a comment. The new code does
*not* try to catch that. The documentation for `ssl.SSLError` says
that it has a `.reason` property, but `python -c 'import ssl;
print(dir(ssl.SSLError("foo", Exception("bar"))))` doesn't mention
that property on either Python 2 or Python 3 on my system. It also
seems that `sslutil` is pretty careful about converting `ssl.SSLError`
to `error.Abort`. It also is carefult to not assume that instances of
the exception have a `.reason`. So I at least don't want to catch
`ssl.SSLError` and handle it the same way as `URLError` because that
would likely result in a crash. I also wonder if we don't need to
handle it at all (because `sslutil` might handle all the cases). It's
now early in the release cycle, so perhaps we can just see how it
goes?

Differential Revision: https://phab.mercurial-scm.org/D9318

/*
 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
	Py_LegacyWindowsStdioFlag = 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;
}