On Fri, 15 Nov 2019, Markus Elfring wrote:
> > --- 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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>
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