Patchwork [v2] exewrapper: prefer HackableMercurial python if availbale

# HG changeset patch
# User Kostia Balytskyi <ikostia@fb.com>
# Date 1489434253 25200
#      Mon Mar 13 12:44:13 2017 -0700
# Node ID 83925d3a3306e7023b4b43757812285b40fcd90b
# Parent  7548522742b5f4f9f5c0881ae4a2783ecda2f969
exewrapper: prefer HackableMercurial python if availbale

Currently hg.exe will only try to load python27.dll from hg-python
subdir if PYTHONHOME environment variable is not set. I think that
it is better to check whether 'hg-python' subdir exists and load
python from it in that case, regardless of environment. This allows
for reliable approach of distributing Mercurial with its own Python.

On Mon, Mar 13, 2017 at 01:06:41PM -0700, Kostia Balytskyi wrote:
> # HG changeset patch
> # User Kostia Balytskyi <ikostia@fb.com>
> # Date 1489434253 25200
> #      Mon Mar 13 12:44:13 2017 -0700
> # Node ID 83925d3a3306e7023b4b43757812285b40fcd90b
> # Parent  7548522742b5f4f9f5c0881ae4a2783ecda2f969
> exewrapper: prefer HackableMercurial python if availbale
> 
> Currently hg.exe will only try to load python27.dll from hg-python
> subdir if PYTHONHOME environment variable is not set. I think that
> it is better to check whether 'hg-python' subdir exists and load
> python from it in that case, regardless of environment. This allows
> for reliable approach of distributing Mercurial with its own Python.

FWIW this looks good to me

On Mon, Mar 13, 2017 at 01:06:41PM -0700, Kostia Balytskyi wrote:
> # HG changeset patch
> # User Kostia Balytskyi <ikostia@fb.com>
> # Date 1489434253 25200
> #      Mon Mar 13 12:44:13 2017 -0700
> # Node ID 83925d3a3306e7023b4b43757812285b40fcd90b
> # Parent  7548522742b5f4f9f5c0881ae4a2783ecda2f969
> exewrapper: prefer HackableMercurial python if availbale

Sure, queued. Seems like the right choice.

>
> Currently hg.exe will only try to load python27.dll from hg-python
> subdir if PYTHONHOME environment variable is not set. I think that
> it is better to check whether 'hg-python' subdir exists and load
> python from it in that case, regardless of environment. This allows
> for reliable approach of distributing Mercurial with its own Python.
>
> diff --git a/mercurial/exewrapper.c b/mercurial/exewrapper.c
> --- a/mercurial/exewrapper.c
> +++ b/mercurial/exewrapper.c
> @@ -67,51 +67,35 @@ int main(int argc, char *argv[])
>       }
>
>       pydll = NULL;
> -	/*
> -	We first check, that environment variable PYTHONHOME is *not* set.
> -	This just mimicks the behavior of the regular python.exe, which uses
> -	PYTHONHOME to find its installation directory (if it has been set).
> -	Note: Users of HackableMercurial are expected to *not* set PYTHONHOME!
> -	*/
> -	if (GetEnvironmentVariable("PYTHONHOME", envpyhome,
> -                                sizeof(envpyhome)) == 0)
> -	{
> -		/*
> -		Environment var PYTHONHOME is *not* set. Let's see if we are
> -		running inside a HackableMercurial.
> -		*/
> +
> +	p = strrchr(pyhome, '\\');
> +	if (p == NULL) {
> +		err = "can't find backslash in module filename";
> +		goto bail;
> +	}
> +	*p = 0; /* cut at directory */
> +
> +	/* check for private Python of HackableMercurial */
> +	strcat_s(pyhome, sizeof(pyhome), "\\hg-python");
>
> -		p = strrchr(pyhome, '\\');
> -		if (p == NULL) {
> -			err = "can't find backslash in module filename";
> +	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);
> +		strcpy_s(pydllfile, sizeof(pydllfile), pyhome);
> +		strcat_s(pydllfile, sizeof(pydllfile), "\\" HGPYTHONLIB ".dll");
> +		pydll = LoadLibrary(pydllfile);
> +		if (pydll == NULL) {
> +			err = "failed to load private Python DLL " HGPYTHONLIB ".dll";
>                       goto bail;
>               }
> -		*p = 0; /* cut at directory */
> -
> -		/* check for private Python of HackableMercurial */
> -		strcat_s(pyhome, sizeof(pyhome), "\\hg-python");
> -
> -		hfind = FindFirstFile(pyhome, &fdata);
> -		if (hfind != INVALID_HANDLE_VALUE) {
> -			/* path pyhome exists, let's use it */
> -			FindClose(hfind);
> -			strcpy_s(pydllfile, sizeof(pydllfile), pyhome);
> -			strcat_s(pydllfile, sizeof(pydllfile),
> -                              "\\" HGPYTHONLIB ".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);
> +		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) {
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