Subject: Re: [PATCH 1/5] convert: initialize attr_action in convert_attrs

From: Torsten Bögershausen <[email-masked]>
Date: Tue, 15 Aug 2017 16:17:34 +0200

On Tue, Aug 15, 2017 at 02:53:01PM +0200, Martin Ågren wrote:
> convert_attrs populates a struct conv_attrs. The field attr_action is
> not set in all code paths, but still one caller unconditionally reads
> it. Since git_check_attr always returns the same value, we'll always end
> up in the same code path and there is no problem right now. But
> convert_attrs is obviously trying not to rely on such an
> implementation-detail of another component.
> 
> Initialize attr_action to CRLF_UNDEFINED in the dead code path.
> 
> Actually, in the code path that /is/ taken, the variable is assigned to
> twice and the first assignment has no effect. That's not wrong, but
> let's remove that first assignment while we're here.
> 
> Signed-off-by: Martin Ågren <[email-masked]>
> ---
> I hit a warning about attr_action possibly being uninitialized when
> building with SANITIZE=thread. I guess it's some random interaction
> between code added by tsan, the optimizer (-O3) and the warning
> machinery. (This was with gcc 5.4.0.)
> 
>  convert.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/convert.c b/convert.c
> index 1012462e3..943d957b4 100644
> --- a/convert.c
> +++ b/convert.c
> @@ -1040,7 +1040,6 @@ static void convert_attrs(struct conv_attrs *ca, const char *path)
>  		ca->crlf_action = git_path_check_crlf(ccheck + 4);
>  		if (ca->crlf_action == CRLF_UNDEFINED)
>  			ca->crlf_action = git_path_check_crlf(ccheck + 0);
> -		ca->attr_action = ca->crlf_action;

I don't think the removal of that line is correct.

>  		ca->ident = git_path_check_ident(ccheck + 1);
>  		ca->drv = git_path_check_convert(ccheck + 2);
>  		if (ca->crlf_action != CRLF_BINARY) {
> @@ -1058,6 +1057,7 @@ static void convert_attrs(struct conv_attrs *ca, const char *path)
>  	} else {
>  		ca->drv = NULL;
>  		ca->crlf_action = CRLF_UNDEFINED;
> +		ca->attr_action = CRLF_UNDEFINED;

But this one can be avoided, when the line
ca->attr_action = ca->crlf_action;
would move completely out of the "if/else" block.

>  		ca->ident = 0;
>  	}
>  	if (ca->crlf_action == CRLF_TEXT)
> -- 
> 2.14.1.151.gdfeca7a7e
> 

Thanks for spotting my mess.
What do you think about the following:

diff --git a/convert.c b/convert.c
index 1012462e3c..fd91b91ada 100644
--- a/convert.c
+++ b/convert.c
@@ -1040,7 +1040,6 @@ static void convert_attrs(struct conv_attrs *ca, const char *path)
 		ca->crlf_action = git_path_check_crlf(ccheck + 4);
 		if (ca->crlf_action == CRLF_UNDEFINED)
 			ca->crlf_action = git_path_check_crlf(ccheck + 0);
-		ca->attr_action = ca->crlf_action;
 		ca->ident = git_path_check_ident(ccheck + 1);
 		ca->drv = git_path_check_convert(ccheck + 2);
 		if (ca->crlf_action != CRLF_BINARY) {
@@ -1060,6 +1059,8 @@ static void convert_attrs(struct conv_attrs *ca, const char *path)
 		ca->crlf_action = CRLF_UNDEFINED;
 		ca->ident = 0;
 	}
+	/* Save attr and make a decision for action */
+	ca->attr_action = ca->crlf_action;
 	if (ca->crlf_action == CRLF_TEXT)
 		ca->crlf_action = text_eol_is_crlf() ? CRLF_TEXT_CRLF : CRLF_TEXT_INPUT;
 	if (ca->crlf_action == CRLF_UNDEFINED && auto_crlf == AUTO_CRLF_FALSE)