threads / patch / 46871

patch, 2 partscoccinelle: add rules to use strbuf_add() for adding buffers to strbufs

Subject: [PATCH 1/2] coccinelle: add rules to use strbuf_add() for adding buffers to strbufs

## tl;dr

3 messages between Oct 1, 2017 and Oct 2, 2017. Diffs are folded; open one to read it.

replies: 2people: 2as markdown or json

René Scharfe· Oct 1, 2017, 14:49 UTC · lore

strbuf_addf() can be used with "%.*s" to add a buffer of a specific size to a strbuf, but the resulting code is longer, may require casting the length to int and is less efficient than simply calling strbuf_add(). Add Coccinelle rules for transforming calls of the former type to the latter.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 contrib/coccinelle/strbuf.cocci | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Show changes to contrib/coccinelle/strbuf.cocci +12 −0

diff --git a/contrib/coccinelle/strbuf.cocci b/contrib/coccinelle/strbuf.cocci
index 1d580e49b0..700a5f9c13 100644
--- a/contrib/coccinelle/strbuf.cocci
+++ b/contrib/coccinelle/strbuf.cocci
@@ -44,3 +44,15 @@ expression E1, E2;
 @@
 - strbuf_addstr(E1, real_path(E2));
 + strbuf_add_real_path(E1, E2);
+
+@@
+expression sb, buf, len;
+@@
+- strbuf_addf(sb, "%.*s", len, buf)
++ strbuf_add(sb, buf, len)
+
+@@
+expression sb, buf, len;
+@@
+- strbuf_addf(sb, "%.*s", (int)(len), buf)
++ strbuf_add(sb, buf, len)

-- 
2.14.2

René Scharfe· Oct 1, 2017, 14:54 UTC · re: René Scharfe · lore

[PATCH 2/2] commit: use strbuf_add() to add a buffer to a strbuf

This is shorter, easier and makes the intent clearer.

Patch generated with Coccinelle and contrib/coccinelle/strbuf.cocci.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 builtin/commit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Show changes to builtin/commit.c +1 −1

diff --git a/builtin/commit.c b/builtin/commit.c
index 0f8ddb6866..d186736617 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -542,7 +542,7 @@ static void export_one(const char *var, const char *s, const char *e, int hack)
 	struct strbuf buf = STRBUF_INIT;
 	if (hack)
 		strbuf_addch(&buf, hack);
-	strbuf_addf(&buf, "%.*s", (int)(e - s), s);
+	strbuf_add(&buf, s, e - s);
 	setenv(var, buf.buf, 1);
 	strbuf_release(&buf);
 }

-- 
2.14.2

Jeff King· Oct 2, 2017, 05:18 UTC · re: René Scharfe · lore

Re: [PATCH 2/2] commit: use strbuf_add() to add a buffer to a strbuf

On Sun, Oct 01, 2017 at 04:54:14PM +0200, René Scharfe wrote:

> This is shorter, easier and makes the intent clearer.
> 
> Patch generated with Coccinelle and contrib/coccinelle/strbuf.cocci.

Technically this behaves differently if there is a NUL embedded in the string. I'd expect that to be unlikely in most cases. And when it is possible, I'd venture to say that the new behavior is likely to be the correct one.

This case is fine (and any embedded NUL would be cut off by setenv anyway). As a general transformation, this is not as obviously safe as many of the others. But since we eyeball the output of coccinelle anyway, it should be fine (and any code which is _relying_ on that behavior really ought to be rewritten in a less subtle way).

-Peff