threads / patch / 57564

patchUse reverse_commit_list helper function for in-place list reversal

Subject: [PATCH] Use reverse_commit_list helper function for in-place list reversal

## tl;dr

5 messages between Mar 15, 2022 and Mar 16, 2022. Diffs are folded; open one to read it.

replies: 4people: 2as markdown or json

Jayati Shrivastava via GitGitGadget· Mar 15, 2022, 19:41 UTC · lore
From: JAYATI SHRIVASTAVA <gaurijove@gmail.com>

Here, a reverse copy of a list is being created by iterating over the list after which the original list is discarded. Instead of creating a new allocation, we can reverse the original list in-place using the reverse_commit_list helper function.

Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
---
    Use reverse_commit_list helper function for in-place list reversal
    
    This patch addresses https://github.com/gitgitgadget/git/issues/1156 . I
    have left builtin/merge.c unmodified since in its case, the original
    list is needed separately from the reverse copy.
    
    (Please excuse if you are receiving this patch again. I had previously
    sent it using git send-email but for some reason the patches are not
    getting delivered to the mailing list despite correctly passing the
    --to/--cc/--in-reply-to options.)
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1177%2Fvictorphoenix3%2Freverse-list-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1177/victorphoenix3/reverse-list-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1177
 sequencer.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
Show changes to sequencer.c +4 −6
diff --git a/sequencer.c b/sequencer.c
index 35006c0cea6..bccbb9e3522 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3749,7 +3749,7 @@ static int do_merge(struct repository *r,
 	int run_commit_flags = 0;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct commit *head_commit, *merge_commit, *i;
-	struct commit_list *bases, *j, *reversed = NULL;
+	struct commit_list *bases, *j;
 	struct commit_list *to_merge = NULL, **tail = &to_merge;
 	const char *strategy = !opts->xopts_nr &&
 		(!opts->strategy ||
@@ -3984,9 +3984,7 @@ static int do_merge(struct repository *r,
 		      git_path_merge_head(r), 0);
 	write_message("no-ff", 5, git_path_merge_mode(r), 0);
 
-	for (j = bases; j; j = j->next)
-		commit_list_insert(j->item, &reversed);
-	free_commit_list(bases);
+	bases = reverse_commit_list(bases);
 
 	repo_read_index(r);
 	init_merge_options(&o, r);
@@ -4002,10 +4000,10 @@ static int do_merge(struct repository *r,
 		 * update the index and working copy immediately.
 		 */
 		ret = merge_ort_recursive(&o,
-					  head_commit, merge_commit, reversed,
+					  head_commit, merge_commit, bases,
 					  &i);
 	} else {
-		ret = merge_recursive(&o, head_commit, merge_commit, reversed,
+		ret = merge_recursive(&o, head_commit, merge_commit, bases,
 				      &i);
 	}
 	if (ret <= 0)

base-commit: b896f729e240d250cf56899e6a0073f6aa469f5d

-- 
gitgitgadget
Junio C Hamano· Mar 15, 2022, 22:53 UTC · re: Jayati Shrivastava via GitGitGadget · lore

Re: [PATCH] Use reverse_commit_list helper function for in-place list reversal

"Jayati Shrivastava via GitGitGadget" <gitgitgadget@gmail.com> writes:

> Subject: Re: [PATCH] Use reverse_commit_list helper function for in-place list reversal
Perhaps
    Subject: [PATCH] sequencer: use reverse_commit_list_helper()
cf. Documentation/SubmittingPatches::[[summary-section]]
> From: JAYATI SHRIVASTAVA <gaurijove@gmail.com>

This name should match what is on Signed-off-by: line. Check your user.name configuration, perhaps?

Show 5 quoted lines
> Here, a reverse copy of a list is being created by iterating
> over the list after which the original list is discarded.
> Instead of creating a new allocation, we can reverse the
> original list in-place using the reverse_commit_list helper
> function.
Perhaps
    Instead of creating a new allocation, reverse the list in-place
    by calling the reverse_commit_list() helper.
cf. Documentation/SubmittingPatches::[[imperative-mood]]
>
> Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
> ---
Show 8 quoted lines
> @@ -3984,9 +3984,7 @@ static int do_merge(struct repository *r,
>  		      git_path_merge_head(r), 0);
>  	write_message("no-ff", 5, git_path_merge_mode(r), 0);
>  
> -	for (j = bases; j; j = j->next)
> -		commit_list_insert(j->item, &reversed);
> -	free_commit_list(bases);
> +	bases = reverse_commit_list(bases);

If the code in the original code that followed from here used both "bases" and "reversed", this would not have worked, but because the original gets rid of "bases", we can just reverse the list in-place with reverse_commit_list() helper and reuse the same variable.

Show 14 quoted lines
>  	repo_read_index(r);
>  	init_merge_options(&o, r);
> @@ -4002,10 +4000,10 @@ static int do_merge(struct repository *r,
>  		 * update the index and working copy immediately.
>  		 */
>  		ret = merge_ort_recursive(&o,
> -					  head_commit, merge_commit, reversed,
> +					  head_commit, merge_commit, bases,
>  					  &i);
>  	} else {
> -		ret = merge_recursive(&o, head_commit, merge_commit, reversed,
> +		ret = merge_recursive(&o, head_commit, merge_commit, bases,
>  				      &i);
>  	}
Looks good.
Thanks.
Jayati Shrivastava via GitGitGadget· Mar 16, 2022, 10:42 UTC · re: Jayati Shrivastava via GitGitGadget · lore

[PATCH v2] sequencer.c: use reverse_commit_list() helper

From: Jayati Shrivastava <gaurijove@gmail.com>

Instead of creating a new allocation, reverse the original list in-place by calling the reverse_commit_list() helper. The original code discards the list "bases" after storing its reverse copy in a newly created list "reversed". If the code that followed from here used both "bases" and "reversed", the modification would not have worked, but since the original list "bases" gets discarded, we can simply reverse "bases" in-place with the reverse_commit_list() helper and reuse the same variable in the code that follows.

Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
---
    Use reverse_commit_list helper function for in-place list reversal
    
    This patch addresses https://github.com/gitgitgadget/git/issues/1156 . I
    have left builtin/merge.c unmodified since in its case, the original
    list is needed separately from the reverse copy.
    
    (Please excuse if you are receiving this patch again. I had previously
    sent it using git send-email but for some reason the patches are not
    getting delivered to the mailing list despite correctly passing the
    --to/--cc/--in-reply-to options.)
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1177%2Fvictorphoenix3%2Freverse-list-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1177/victorphoenix3/reverse-list-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1177
Range-diff vs v1:
 1:  8c3c6c9ed4c ! 1:  f794bcd8bda Use reverse_commit_list helper function for in-place list reversal
     @@
       ## Metadata ##
     -Author: JAYATI SHRIVASTAVA <gaurijove@gmail.com>
     +Author: Jayati Shrivastava <gaurijove@gmail.com>
      
       ## Commit message ##
     -    Use reverse_commit_list helper function for in-place list reversal
     +    sequencer.c: use reverse_commit_list() helper
      
     -    Here, a reverse copy of a list is being created by iterating
     -    over the list after which the original list is discarded.
     -    Instead of creating a new allocation, we can reverse the
     -    original list in-place using the reverse_commit_list helper
     -    function.
     +    Instead of creating a new allocation, reverse the original
     +    list in-place by calling the reverse_commit_list() helper.
     +    The original code discards the list "bases" after storing
     +    its reverse copy in a newly created list "reversed". If the
     +    code that followed from here used both "bases" and "reversed",
     +    the modification would not have worked, but since the original
     +    list "bases" gets discarded, we can simply reverse "bases"
     +    in-place with the reverse_commit_list() helper and reuse the
     +    same variable in the code that follows.
      
          Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
      
 sequencer.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
Show changes to sequencer.c +4 −6
diff --git a/sequencer.c b/sequencer.c
index 35006c0cea6..bccbb9e3522 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3749,7 +3749,7 @@ static int do_merge(struct repository *r,
 	int run_commit_flags = 0;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct commit *head_commit, *merge_commit, *i;
-	struct commit_list *bases, *j, *reversed = NULL;
+	struct commit_list *bases, *j;
 	struct commit_list *to_merge = NULL, **tail = &to_merge;
 	const char *strategy = !opts->xopts_nr &&
 		(!opts->strategy ||
@@ -3984,9 +3984,7 @@ static int do_merge(struct repository *r,
 		      git_path_merge_head(r), 0);
 	write_message("no-ff", 5, git_path_merge_mode(r), 0);
 
-	for (j = bases; j; j = j->next)
-		commit_list_insert(j->item, &reversed);
-	free_commit_list(bases);
+	bases = reverse_commit_list(bases);
 
 	repo_read_index(r);
 	init_merge_options(&o, r);
@@ -4002,10 +4000,10 @@ static int do_merge(struct repository *r,
 		 * update the index and working copy immediately.
 		 */
 		ret = merge_ort_recursive(&o,
-					  head_commit, merge_commit, reversed,
+					  head_commit, merge_commit, bases,
 					  &i);
 	} else {
-		ret = merge_recursive(&o, head_commit, merge_commit, reversed,
+		ret = merge_recursive(&o, head_commit, merge_commit, bases,
 				      &i);
 	}
 	if (ret <= 0)

base-commit: b896f729e240d250cf56899e6a0073f6aa469f5d

-- 
gitgitgadget
Jayati Shrivastava via GitGitGadget· Mar 16, 2022, 11:20 UTC · re: Jayati Shrivastava via GitGitGadget · lore

[PATCH v3] sequencer.c: use reverse_commit_list() helper

From: Jayati Shrivastava <gaurijove@gmail.com>

Instead of creating a new allocation, reverse the original list in-place by calling the reverse_commit_list() helper. The original code discards the list "bases" after storing its reverse copy in a newly created list "reversed". If the code that followed from here used both "bases" and "reversed", the modification would not have worked, but since the original list "bases" gets discarded, we can simply reverse "bases" in-place with the reverse_commit_list() helper and reuse the same variable in the code that follows.

builtin/merge.c has been left unmodified, since in its case, the original list is needed separately from its reverse copy by the code.

Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
---
    Use reverse_commit_list helper function for in-place list reversal
    
    This patch address https://github.com/gitgitgadget/git/issues/1156
    Changes since v2:
    
     * updated the commit message to explain why builtin/merge.c has not
       been modified
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1177%2Fvictorphoenix3%2Freverse-list-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1177/victorphoenix3/reverse-list-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1177
Range-diff vs v2:
 1:  f794bcd8bda ! 1:  6dd0d92096b sequencer.c: use reverse_commit_list() helper
     @@ Metadata
       ## Commit message ##
          sequencer.c: use reverse_commit_list() helper
      
     -    Instead of creating a new allocation, reverse the original
     -    list in-place by calling the reverse_commit_list() helper.
     -    The original code discards the list "bases" after storing
     -    its reverse copy in a newly created list "reversed". If the
     -    code that followed from here used both "bases" and "reversed",
     -    the modification would not have worked, but since the original
     -    list "bases" gets discarded, we can simply reverse "bases"
     -    in-place with the reverse_commit_list() helper and reuse the
     -    same variable in the code that follows.
     +    Instead of creating a new allocation, reverse the
     +    original list in-place by calling the
     +    reverse_commit_list() helper. The original code
     +    discards the list "bases" after storing its
     +    reverse copy in a newly created list "reversed".
     +    If the code that followed from here used both
     +    "bases" and "reversed", the modification would not
     +    have worked, but since the original list "bases"
     +    gets discarded, we can simply reverse "bases"
     +    in-place with the reverse_commit_list() helper and
     +    reuse the same variable in the code that follows.
     +
     +    builtin/merge.c has been left unmodified, since in
     +    its case, the original list is needed separately
     +    from its reverse copy by the code.
      
          Signed-off-by: Jayati Shrivastava <gaurijove@gmail.com>
      
 sequencer.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
Show changes to sequencer.c +4 −6
diff --git a/sequencer.c b/sequencer.c
index 35006c0cea6..bccbb9e3522 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3749,7 +3749,7 @@ static int do_merge(struct repository *r,
 	int run_commit_flags = 0;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct commit *head_commit, *merge_commit, *i;
-	struct commit_list *bases, *j, *reversed = NULL;
+	struct commit_list *bases, *j;
 	struct commit_list *to_merge = NULL, **tail = &to_merge;
 	const char *strategy = !opts->xopts_nr &&
 		(!opts->strategy ||
@@ -3984,9 +3984,7 @@ static int do_merge(struct repository *r,
 		      git_path_merge_head(r), 0);
 	write_message("no-ff", 5, git_path_merge_mode(r), 0);
 
-	for (j = bases; j; j = j->next)
-		commit_list_insert(j->item, &reversed);
-	free_commit_list(bases);
+	bases = reverse_commit_list(bases);
 
 	repo_read_index(r);
 	init_merge_options(&o, r);
@@ -4002,10 +4000,10 @@ static int do_merge(struct repository *r,
 		 * update the index and working copy immediately.
 		 */
 		ret = merge_ort_recursive(&o,
-					  head_commit, merge_commit, reversed,
+					  head_commit, merge_commit, bases,
 					  &i);
 	} else {
-		ret = merge_recursive(&o, head_commit, merge_commit, reversed,
+		ret = merge_recursive(&o, head_commit, merge_commit, bases,
 				      &i);
 	}
 	if (ret <= 0)

base-commit: b896f729e240d250cf56899e6a0073f6aa469f5d

-- 
gitgitgadget
Junio C Hamano· Mar 16, 2022, 19:44 UTC · re: Jayati Shrivastava via GitGitGadget · lore

Re: [PATCH v3] sequencer.c: use reverse_commit_list() helper

"Jayati Shrivastava via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 5 quoted lines
> From: Jayati Shrivastava <gaurijove@gmail.com>
>
> Instead of creating a new allocation, reverse the
> original list in-place by calling the
> reverse_commit_list() helper.

OK. I recall that v2 wrapped with longer lines that was easier to read.

Show 9 quoted lines
> The original code
> discards the list "bases" after storing its
> reverse copy in a newly created list "reversed".
> If the code that followed from here used both
> "bases" and "reversed", the modification would not
> have worked, but since the original list "bases"
> gets discarded, we can simply reverse "bases"
> in-place with the reverse_commit_list() helper and
> reuse the same variable in the code that follows.

I am 30% surprised to see this in the log message ;-). There is nothing incorrect in the description per-se, but it is something I would expect in a review that reads a patch and follows along thinking aloud to see if the code makes sense, or below "---", but it does explain why the patch chose to lose the extra variable, so probably it is OK.

> builtin/merge.c has been left unmodified, since in its case, the
> original list is needed separately from its reverse copy by the
> code.
Good.
The patch text looks good, too.
Thanks.

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