From: Johannes Sixt <j6t@kdbg.org>
Date: Tue, 11 Dec 2018 20:36:06 GMT
Subject: Re: [PATCH 2/2] mingw: allow absolute paths without drive prefix
Message-ID: <8a484f86-1d43-fc0a-22b4-39c770cda6cb@kdbg.org>
In-Reply-To: <nycvar.QRO.7.76.6.1812111134250.43@tvgsbejvaqbjf.bet>

Am 11.12.18 um 12:25 schrieb Johannes Schindelin:
> On Mon, 10 Dec 2018, Johannes Sixt wrote:
>>> diff --git a/compat/mingw.c b/compat/mingw.c
>>> index 34b3880b29..4d009901d8 100644
>>> --- a/compat/mingw.c
>>> +++ b/compat/mingw.c
>>> @@ -928,11 +928,19 @@ unsigned int sleep (unsigned int seconds)
>>>    char *mingw_mktemp(char *template)
>>>    {
>>>    	wchar_t wtemplate[MAX_PATH];
>>> +	int offset = 0;
>>> +
>>>     if (xutftowcs_path(wtemplate, template) < 0)
>>>    		return NULL;
>>> +
>>> +	if (is_dir_sep(template[0]) && !is_dir_sep(template[1]) &&
>>> +	    iswalpha(wtemplate[0]) && wtemplate[1] == L':') {
>>> +		/* We have an absolute path missing the drive prefix */
>>
>> This comment is true for the source part, template, but I can't find
>> where the destination, wtemplate, suddenly gets the drive prefix. As far
>> as I can see, xutftowcs_path() just does a plain textual conversion
>> without any interpretation of the text as path. Can you explain it?
> 
> It is legal on Windows for such a path to lack the drive prefix, also in
> the wide-character version. So the explanation is: even `wtemplate` won't
> get the drive prefix. It does not need to.

I'm sorry, my question was extremely fuzzy. I actually wanted to know 
how the condition that you introduce in this patch can ever be true.

And after looking at the Git for Windows code, I could answer it myself: 
it cannot. Not with this patch alone. In GfW, there is additional code 
in xutftowcs_path() that massages wtemplate to receive a drive prefix; 
but vanilla Git does not have that code, so that is_dir_sep(template[0]) 
and iswalpha(wtemplate[0]) can never be true at the same time at this point.

-- Hannes