[PATCH] diff: remove another ternary expression always evaluating to true

[PATCH] diff: remove another ternary expression always evaluating to true

[Stefan Beller]

The condition before the changed line dereferences 'one' to query the mode,
so if the condition evaluates to true, the variable one must not be null.
Therefore we do not need the ternary operator depending on one, giving
either one->path or two->path. This always evaluates to one->path, so
we can remove the ternary operator.

The condition and the usage of the ternary operator have been introduced
by the same commit (752c0c24, 2009-10-19, Add the --submodule option to
the diff option family). As that commit message refers to a GitTogether
I'd assume that patch was crafted in a hurry, so maybe overlooking the
need for a ternary operator there.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
---
 diff.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/diff.c b/diff.c
index 80f8439..f30b7e4 100644
--- a/diff.c
+++ b/diff.c
@@ -2252,8 +2252,7 @@ static void builtin_diff(const char *name_a,
 			(!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
-		show_submodule_summary(o->file, one ? one->path : two->path,
-				line_prefix,
+		show_submodule_summary(o->file, one->path, line_prefix,
 				one->sha1, two->sha1, two->dirty_submodule,
 				meta, del, add, reset);
 		return;
-- 
1.8.4.rc1.25.gd121ba2

Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Johannes Schindelin]

Hi Stefan,

On Thu, 8 Aug 2013, Stefan Beller wrote:

> The condition before the changed line dereferences 'one' to query the mode,
> so if the condition evaluates to true, the variable one must not be null.

To show this better, please use -U10 (or some other appropriate context
option) in the future.

> Therefore we do not need the ternary operator depending on one, giving
> either one->path or two->path. This always evaluates to one->path, so we
> can remove the ternary operator.
> 
> The condition and the usage of the ternary operator have been introduced
> by the same commit (752c0c24, 2009-10-19, Add the --submodule option to
> the diff option family). As that commit message refers to a GitTogether
> I'd assume that patch was crafted in a hurry, so maybe overlooking the
> need for a ternary operator there.

If this is my code, I do not need a GitTogether to excuse my sloppiness.
In this particular case, I imagine the appropriate fix is to test for
one->path instead of removing the conditional, though.

Ciao,
Johannes

Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Stefan Beller]

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On 08/08/2013 11:01 PM, Johannes Schindelin wrote:
> Hi Stefan,
> 
> On Thu, 8 Aug 2013, Stefan Beller wrote:
> 
>> The condition before the changed line dereferences 'one' to query the mode,
>> so if the condition evaluates to true, the variable one must not be null.
> 
> To show this better, please use -U10 (or some other appropriate context
> option) in the future.
> 
>> Therefore we do not need the ternary operator depending on one, giving
>> either one->path or two->path. This always evaluates to one->path, so we
>> can remove the ternary operator.
>>
>> The condition and the usage of the ternary operator have been introduced
>> by the same commit (752c0c24, 2009-10-19, Add the --submodule option to
>> the diff option family). As that commit message refers to a GitTogether
>> I'd assume that patch was crafted in a hurry, so maybe overlooking the
>> need for a ternary operator there.
> 
> If this is my code, I do not need a GitTogether to excuse my sloppiness.
> In this particular case, I imagine the appropriate fix is to test for
> one->path instead of removing the conditional, though.
> 
> Ciao,
> Johannes
> 

Ok, here is a resend with -U10
I forgot about the -U10 as gitk shows a different number of lines 
of context around. Is there a way to configure gitk to show less lines
of code or a default -U10 for send-email/format-patch?

So you rather propose to have 
-		show_submodule_summary(o->file, one ? one->path : two->path,
+		show_submodule_summary(o->file, one->path ? one->path : two->path,

instead of the patch below?
(The test suite run without any problem using that patch)

Stefan

--8<--
From 3a580c51f0bf70745f26eb5045d646dfead2afd3 Mon Sep 17 00:00:00 2001
From: Stefan Beller <stefanbeller@googlemail.com>
Date: Thu, 8 Aug 2013 20:54:24 +0200
Subject: [PATCH] diff: remove another ternary expression always evaluating to
 true

The condition before the changed line dereferences 'one' to query the mode,
so if the condition evaluates to true, the variable one must not be null.
Therefore we do not need the ternary operator depending on one, giving
either one->path or two->path. This always evaluates to one->path, so
we can remove the ternary operator.

The condition and the usage of the ternary operator have been introduced
by the same commit (752c0c24, 2009-10-19, Add the --submodule option to
the diff option family). As that commit message refers to a GitTogether
I'd assume that patch was crafted in a hurry, so maybe overlooking the
need for a ternary operator there.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
---
 diff.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/diff.c b/diff.c
index 80f8439..f30b7e4 100644
--- a/diff.c
+++ b/diff.c
@@ -2245,22 +2245,21 @@ static void builtin_diff(const char *name_a,
 	struct userdiff_driver *textconv_one = NULL;
 	struct userdiff_driver *textconv_two = NULL;
 	struct strbuf header = STRBUF_INIT;
 	const char *line_prefix = diff_line_prefix(o);
 
 	if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
 			(!one->mode || S_ISGITLINK(one->mode)) &&
 			(!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
-		show_submodule_summary(o->file, one ? one->path : two->path,
-				line_prefix,
+		show_submodule_summary(o->file, one->path, line_prefix,
 				one->sha1, two->sha1, two->dirty_submodule,
 				meta, del, add, reset);
 		return;
 	}
 
 	if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
 		textconv_one = get_textconv(one);
 		textconv_two = get_textconv(two);
 	}
 
-- 
1.8.4.rc1.25.gd121ba2



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Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Johannes Schindelin]

Hi Stefan,

On Thu, 8 Aug 2013, Stefan Beller wrote:

> So you rather propose to have 
> -		show_submodule_summary(o->file, one ? one->path : two->path,
> +		show_submodule_summary(o->file, one->path ? one->path : two->path,

I do. The reason is that one->path could be NULL (but not both one->path
and two->path) and the summary would not be as helpful as possible if it
wrote "(null)" instead of the path of the submodule.

Ciao,
Johannes

Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Philip Oakley]

From: "Stefan Beller" <stefanbeller@googlemail.com>
Sent: Thursday, August 08, 2013 7:55 PM
Subject: [PATCH] diff: remove another ternary expression always 
evaluating to true

Have these issues (and the earlier expression simplifications patches 
$gmane/231916, $gmane/231912 ) been discovered with the "STACK" tool I'd 
noted in $gmane/230542 which you were also interested in (I've not had 
chance to run the tool).

If so, it's probably worth referencing the tool and the paper which 
explains the broader issues.

Philip


> The condition before the changed line dereferences 'one' to query the 
> mode,
> so if the condition evaluates to true, the variable one must not be 
> null.
> Therefore we do not need the ternary operator depending on one, giving
> either one->path or two->path. This always evaluates to one->path, so
> we can remove the ternary operator.
>
> The condition and the usage of the ternary operator have been 
> introduced
> by the same commit (752c0c24, 2009-10-19, Add the --submodule option 
> to
> the diff option family). As that commit message refers to a 
> GitTogether
> I'd assume that patch was crafted in a hurry, so maybe overlooking the
> need for a ternary operator there.
>
> Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
> ---
> diff.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/diff.c b/diff.c
> index 80f8439..f30b7e4 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -2252,8 +2252,7 @@ static void builtin_diff(const char *name_a,
>  (!two->mode || S_ISGITLINK(two->mode))) {
>  const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
>  const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
> - show_submodule_summary(o->file, one ? one->path : two->path,
> - line_prefix,
> + show_submodule_summary(o->file, one->path, line_prefix,
>  one->sha1, two->sha1, two->dirty_submodule,
>  meta, del, add, reset);
>  return;
> -- 
> 1.8.4.rc1.25.gd121ba2
>
> --

Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Hi Stefan,
>
> On Thu, 8 Aug 2013, Stefan Beller wrote:
>
>> So you rather propose to have 
>> -		show_submodule_summary(o->file, one ? one->path : two->path,
>> +		show_submodule_summary(o->file, one->path ? one->path : two->path,
>
> I do. The reason is that one->path could be NULL (but not both one->path
> and two->path) and the summary would not be as helpful as possible if it
> wrote "(null)" instead of the path of the submodule.

Good.

Also some C libraries would choke when asked to %s format a NULL,
instead of giving "(null)" to avoid segfaulting (which I think is a
quirk in glibc).

[PATCH] diff: fix a possible null pointer dereference

[Stefan Beller]

The condition in the ternary operator was wrong, hence the wrong char
pointer could be used as the parameter for show_submodule_summary.
one->path may be null, but we definitely need a non null path given
to the function.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Acked-By: Johannes Schindelin <Johannes.Schindelin@gmx.de>
---
 diff.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/diff.c b/diff.c
index 80f8439..061694b 100644
--- a/diff.c
+++ b/diff.c
@@ -2252,7 +2252,7 @@ static void builtin_diff(const char *name_a,
 			(!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
-		show_submodule_summary(o->file, one ? one->path : two->path,
+		show_submodule_summary(o->file, one->path ? one->path : two->path,
 				line_prefix,
 				one->sha1, two->sha1, two->dirty_submodule,
 				meta, del, add, reset);
-- 
1.8.4.rc1.25.gd121ba2

Re: [PATCH] diff: remove another ternary expression always evaluating to true

[Stefan Beller]

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On 08/08/2013 11:36 PM, Philip Oakley wrote:
> From: "Stefan Beller" <stefanbeller@googlemail.com>
> Sent: Thursday, August 08, 2013 7:55 PM
> Subject: [PATCH] diff: remove another ternary expression always
> evaluating to true
> 
> Have these issues (and the earlier expression simplifications patches
> $gmane/231916, $gmane/231912 ) been discovered with the "STACK" tool I'd
> noted in $gmane/230542 which you were also interested in (I've not had
> chance to run the tool).
> 
> If so, it's probably worth referencing the tool and the paper which
> explains the broader issues.
> 
> Philip
> 

Yes, those 3 issues have been discovered using the STACK tool
The paper regarding that tool can be found at
http://pdos.csail.mit.edu/~xi/papers/stack-sosp13.pdf

It's definitely an interesting read! (At least for me it was ;)
The authors intend to make that tool available to broader public
as open source in August this year, iirc.

However I do not know if their repository address was
already announced publicly, so I did not announce to have used it.
(Last time I announced using static code analysis tools for
my patches the review-process was much harder as well :D)

Stefan


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