strbuf.cocci: suggest strbuf_addbuf() to add one strbuf to an other

szeder · gitster · commit 28c23cd4c390 · 2019-01-27T16:21:09.000-08:00
The best way to add one strbuf to an other is via:

  strbuf_addbuf(&amp;sb, &amp;sb2);

This is a bit more idiomatic and efficient than:

  strbuf_addstr(&amp;sb, sb2.buf);

because the size of the second strbuf is known and thus it can spare a
strlen() call, and much more so than:

  strbuf_addf(&amp;sb, "%s", sb2.buf);

because it can spare the whole vsnprintf() formatting magic.

Add new semantic patches to 'contrib/coccinelle/strbuf.cocci' to catch
these undesired patterns and to suggest strbuf_addbuf() instead.

Luckily, our codebase is already clean from any such undesired
patterns (but one of the in-flight topics just tried to sneak in such
a strbuf_addf() call).

Signed-off-by: SZEDER Gábor &lt;szeder.dev@gmail.com&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/contrib/coccinelle/strbuf.cocci b/contrib/coccinelle/strbuf.cocci
@@ -12,6 +12,36 @@ constant fmt !~ "%";
 )
   );
 
+@@
+expression E;
+struct strbuf SB;
+format F =~ "s";
+@@
+- strbuf_addf(E, "%@F@", SB.buf);
++ strbuf_addbuf(E, &SB);
+
+@@
+expression E;
+struct strbuf *SBP;
+format F =~ "s";
+@@
+- strbuf_addf(E, "%@F@", SBP->buf);
++ strbuf_addbuf(E, SBP);
+
+@@
+expression E;
+struct strbuf SB;
+@@
+- strbuf_addstr(E, SB.buf);
++ strbuf_addbuf(E, &SB);
+
+@@
+expression E;
+struct strbuf *SBP;
+@@
+- strbuf_addstr(E, SBP->buf);
++ strbuf_addbuf(E, SBP);
+
 @@
 expression E1, E2;
 format F =~ "s";
