Re: [Cocci] git-coccinelle: adjustments for array.cocci?

On Fri, 15 Nov 2019, Markus Elfring wrote:

quoted

--- array-released.diff	2019-11-14 21:29:11.020576916 +0100
+++ array-reduced1.diff	2019-11-14 21:45:58.931956527 +0100

@@ -6,24 +6,10 @@
  	r->entry_count = t->entry_count;
  	r->delta_depth = t->delta_depth;
 -	memcpy(r->entries,t->entries,t->entry_count*sizeof(t->entries[0]));
-+	COPY_ARRAY(r->entries, t->entries, t->entry_count);
++	memcpy(r->entries,t->entries,t->entry_count*sizeof(*(t->entries)));
  	release_tree_content(t);
  	return r;
  }

It took a while to become more aware of software development challenges
for the safe data processing with the semantic patch language also
at such a source code place.
https://github.com/git/git/blob/3edfcc65fdfc708c1c8f1d314885eecf9beb9b67/fast-import.c#L640

I got the impression that the Coccinelle software is occasionally able
to determine from the search specification “sizeof(T)” the corresponding
data type for code like “*(t->entries)”.

It can determine the type of t->entries if it has access to the definition
of the type of t.  This type may be in a header file.  If you want
Coccinelle to be able to find this information you can use the option
--all-includes or --recursive-includes.  It will be more efficient with
the option --include-headers-for-types.

julia

But it seems that there are circumstances to consider where the desired
data type was not automatically determined.
Thus the data processing  can become safer by explicitly expressing
the case distinction for the handling of expressions.

Adjusted transformation rule:
@@
type T;
T* dst_ptr, src_ptr;
T[] dst_arr, src_arr;
expression n, x;
@@
-memcpy
+COPY_ARRAY
       (
(       dst_ptr
|       dst_arr
)
       ,
(       src_ptr
|       src_arr
)
       ,
-       (n) * \( sizeof(T) \| sizeof(*(x)) \)
+       n
       )


Regards,
Markus
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