[2/2] mingw: allow absolute paths without drive prefix
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Message ID 50ac31ef7f4380f37a0e2d3b75e82b324afee9e3.1544467631.git.gitgitgadget@gmail.com
State New
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Series
  • mingw: support absolute paths without a drive prefix
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Commit Message

Derrick Stolee via GitGitGadget Dec. 10, 2018, 6:47 p.m. UTC
From: Johannes Schindelin <johannes.schindelin@gmx.de>

When specifying an absolute path without a drive prefix, we convert that
path internally. Let's make sure that we handle that case properly, too
;-)

This fixes the command

	git clone https://github.com/git-for-windows/git \G4W

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/mingw.c            | 10 +++++++++-
 t/t5580-clone-push-unc.sh |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

Comments

Johannes Sixt Dec. 10, 2018, 9:58 p.m. UTC | #1
Am 10.12.18 um 19:47 schrieb Johannes Schindelin via GitGitGadget:
> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> When specifying an absolute path without a drive prefix, we convert that
> path internally. Let's make sure that we handle that case properly, too
> ;-)
> 
> This fixes the command
> 
> 	git clone https://github.com/git-for-windows/git \G4W
> 
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>   compat/mingw.c            | 10 +++++++++-
>   t/t5580-clone-push-unc.sh |  2 +-
>   2 files changed, 10 insertions(+), 2 deletions(-)
> 
> 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?

BTW, iswalpha() is not restricted to ASCII letters, I would rewrite it 
as (wtemplate[0] <= 127 && isalpha(wtemplate[0]).

> +		offset = 2;
> +	}
>   	if (!_wmktemp(wtemplate))
>   		return NULL;
> -	if (xwcstoutf(template, wtemplate, strlen(template) + 1) < 0)
> +	if (xwcstoutf(template, wtemplate + offset, strlen(template) + 1) < 0)
>   		return NULL;
>   	return template;
>   }
> diff --git a/t/t5580-clone-push-unc.sh b/t/t5580-clone-push-unc.sh
> index c2b0082296..17c38c33a5 100755
> --- a/t/t5580-clone-push-unc.sh
> +++ b/t/t5580-clone-push-unc.sh
> @@ -29,7 +29,7 @@ case "$UNCPATH" in
>   	;;
>   esac
>   
> -test_expect_failure 'clone into absolute path lacking a drive prefix' '
> +test_expect_success 'clone into absolute path lacking a drive prefix' '
>   	USINGBACKSLASHES="$(echo "$WITHOUTDRIVE"/without-drive-prefix |
>   		tr / \\\\)" &&
>   	git clone . "$USINGBACKSLASHES" &&
> 

-- Hannes
Johannes Schindelin Dec. 11, 2018, 11:25 a.m. UTC | #2
Hi Hannes,

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.

> BTW, iswalpha() is not restricted to ASCII letters, I would rewrite it
> as (wtemplate[0] <= 127 && isalpha(wtemplate[0]).

Very good point! Will fix.

Thanks,
Dscho
Johannes Sixt Dec. 11, 2018, 8:36 p.m. UTC | #3
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
Junio C Hamano Dec. 13, 2018, 2:48 a.m. UTC | #4
Johannes Sixt <j6t@kdbg.org> writes:

>>>> +	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.

So,... what's the conclusion?  The patch in the context of my tree
would be a no-op, and we'd need a prerequisite change to the support
function to accompany this patch to be effective?
Johannes Sixt Dec. 13, 2018, 6:25 a.m. UTC | #5
Am 13.12.18 um 03:48 schrieb Junio C Hamano:
> So,... what's the conclusion?  The patch in the context of my tree
> would be a no-op, and we'd need a prerequisite change to the support
> function to accompany this patch to be effective?

Correct, that is my conclusion.

-- Hannes
Johannes Sixt Dec. 13, 2018, 7:38 p.m. UTC | #6
Am 13.12.18 um 07:25 schrieb Johannes Sixt:
> Am 13.12.18 um 03:48 schrieb Junio C Hamano:
>> So,... what's the conclusion?  The patch in the context of my tree
>> would be a no-op, and we'd need a prerequisite change to the support
>> function to accompany this patch to be effective?
> 
> Correct, that is my conclusion.

Moreover, there is no problem with your tree to begin with. I cloned 
into a destination without a drive letter:

C:\>git clone R:\j6t\expat.git \Temp\expat
Cloning into '\Temp\expat'...
done.

and it works fine. If I understood the description in patch 1/2 
correctly, this should have failed.

-- Hannes
Johannes Schindelin Dec. 14, 2018, 11:31 a.m. UTC | #7
Hi Hannes,

On Thu, 13 Dec 2018, Johannes Sixt wrote:

> Am 13.12.18 um 07:25 schrieb Johannes Sixt:
> > Am 13.12.18 um 03:48 schrieb Junio C Hamano:
> > > So,... what's the conclusion?  The patch in the context of my tree
> > > would be a no-op, and we'd need a prerequisite change to the support
> > > function to accompany this patch to be effective?
> > 
> > Correct, that is my conclusion.
> 
> Moreover, there is no problem with your tree to begin with. I cloned into a
> destination without a drive letter:
> 
> C:\>git clone R:\j6t\expat.git \Temp\expat
> Cloning into '\Temp\expat'...
> done.
> 
> and it works fine. If I understood the description in patch 1/2 correctly,
> this should have failed.

Thank you for the analysis. I'll look which patches in Git for Windows
introduced that regression, then, and fold this here patch series into
that one.

Thanks,
Dscho

Patch
diff mbox series

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 */
+		offset = 2;
+	}
 	if (!_wmktemp(wtemplate))
 		return NULL;
-	if (xwcstoutf(template, wtemplate, strlen(template) + 1) < 0)
+	if (xwcstoutf(template, wtemplate + offset, strlen(template) + 1) < 0)
 		return NULL;
 	return template;
 }
diff --git a/t/t5580-clone-push-unc.sh b/t/t5580-clone-push-unc.sh
index c2b0082296..17c38c33a5 100755
--- a/t/t5580-clone-push-unc.sh
+++ b/t/t5580-clone-push-unc.sh
@@ -29,7 +29,7 @@  case "$UNCPATH" in
 	;;
 esac
 
-test_expect_failure 'clone into absolute path lacking a drive prefix' '
+test_expect_success 'clone into absolute path lacking a drive prefix' '
 	USINGBACKSLASHES="$(echo "$WITHOUTDRIVE"/without-drive-prefix |
 		tr / \\\\)" &&
 	git clone . "$USINGBACKSLASHES" &&