On Tue, Dec 06 2022, Taylor Blau wrote:

On Mon, Dec 05, 2022 at 08:43:50PM -0500, Jeff King wrote:

quoted

On Mon, Dec 05, 2022 at 05:36:25PM -0500, Taylor Blau wrote:

quoted

On Mon, Dec 05, 2022 at 10:01:11PM +0100, René Scharfe wrote:

quoted

This rule would turn this code:

	struct foo *bar = xcalloc(1, sizeof(*bar));
	int i;

... into:

	struct foo *bar;
	CALLOC(bar);
	int i;

... which violates the coding guideline to not mix declarations and
statements (-Wdeclaration-after-statement).

Yeah, I was wondering about this myself when I wrote this part of the
Coccinelle patch.

Is there an intelligent way to tell it to put the first statement after
all declarations? I couldn't find anything after a quick scan of the
documentation nor our own patches.

It feels like generating the code as above is not the end of the world.
The most valuable thing that coccinelle is doing here is _finding_ the
location, and telling you "it's supposed to be like this". It is great
when the "this" post-image is perfect and doesn't need further tweaking.

I have to agree. If Coccinelle can generate the right output; great. But
if it can't, the amount of additional work to reorganize an already
generated and mostly correct *.patch from the tool seems minimal by
comparison.

It can, but you need to write your semantic patch to match your
intent. If you write e.g.:

	- int x;
        + int y;
        + foo();

That means "add the int y and foo() line right after that "int x" line
you removed.

Whereas what you want in this case is closer to:

 - match the "int x" line
 - remove or amend it
 - skip past all subsequent declarations
 - skip past all code that isn't referring to the "x variable?
 - insert the "CALLOC_ARRAY" (or whatever) before that first "x" use.

I don't know offhand how to match this, but presumably it's some mixture
of the wildcard syntax ("...", "<... ...>" etc.) and matching a
"statement", or maybe marking the "int x" with the "@pos" syntax, and
referring to that position again.

I usually just browse through the coccinelle.git for *.cocci examples
and/or read the PDF (*not* the manual page, which discusses almost none
of the syntax) documentation.

See:

	git grep -F '...' -- contrib/coccinelle 

For some in-tree use of this, the unused.cocci I added recently is
probably the closest equivalent to what you'll want.