[PATCH 1/2] coccinelle: use COPY_ARRAY for copying arrays

[PATCH 1/2] coccinelle: use COPY_ARRAY for copying arrays

[René Scharfe]

The current semantic patch for COPY_ARRAY transforms memcpy(3) calls on
pointers, but Coccinelle distinguishes them from arrays.  It already
contains three rules to handle the options for sizeof (i.e. source,
destination and type), and handling arrays as source and destination
would require four times as many rules if we enumerated all cases.

We also don't handle array subscripts, and supporting that would
increase the number of rules by another factor of four.  (An isomorphism
telling Coccinelle that "sizeof x[...]" is equivalent to "sizeof *x"
would be nice..)

Support arrays and array subscripts, but keep the number of rules down
by adding normalization steps: First turn array subscripts into
derefences, then determine the types of expressions used with sizeof and
replace them with these types, and then convert the different possible
combinations of arrays and pointers with memcpy(3) to COPY_ARRAY.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 contrib/coccinelle/array.cocci | 61 +++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 15 deletions(-)

diff --git a/contrib/coccinelle/array.cocci b/contrib/coccinelle/array.cocci
index 01586821dc..46b8d2ee11 100644
--- a/contrib/coccinelle/array.cocci
+++ b/contrib/coccinelle/array.cocci
@@ -1,29 +1,60 @@
 @@
-type T;
-T *dst;
-T *src;
-expression n;
+expression dst, src, n, E;
 @@
-- memcpy(dst, src, (n) * sizeof(*dst));
-+ COPY_ARRAY(dst, src, n);
+  memcpy(dst, src, n * sizeof(
+- E[...]
++ *(E)
+  ))

 @@
 type T;
-T *dst;
-T *src;
-expression n;
+T *ptr;
+T[] arr;
+expression E, n;
 @@
-- memcpy(dst, src, (n) * sizeof(*src));
-+ COPY_ARRAY(dst, src, n);
+(
+  memcpy(ptr, E,
+- n * sizeof(*(ptr))
++ n * sizeof(T)
+  )
+|
+  memcpy(arr, E,
+- n * sizeof(*(arr))
++ n * sizeof(T)
+  )
+|
+  memcpy(E, ptr,
+- n * sizeof(*(ptr))
++ n * sizeof(T)
+  )
+|
+  memcpy(E, arr,
+- n * sizeof(*(arr))
++ n * sizeof(T)
+  )
+)

 @@
 type T;
-T *dst;
-T *src;
+T *dst_ptr;
+T *src_ptr;
+T[] dst_arr;
+T[] src_arr;
 expression n;
 @@
-- memcpy(dst, src, (n) * sizeof(T));
-+ COPY_ARRAY(dst, src, n);
+(
+- memcpy(dst_ptr, src_ptr, (n) * sizeof(T))
++ COPY_ARRAY(dst_ptr, src_ptr, n)
+|
+- memcpy(dst_ptr, src_arr, (n) * sizeof(T))
++ COPY_ARRAY(dst_ptr, src_arr, n)
+|
+- memcpy(dst_arr, src_ptr, (n) * sizeof(T))
++ COPY_ARRAY(dst_arr, src_ptr, n)
+|
+- memcpy(dst_arr, src_arr, (n) * sizeof(T))
++ COPY_ARRAY(dst_arr, src_arr, n)
+)

 @@
 type T;
--
2.22.0

[PATCH 2/2] use COPY_ARRAY for copying arrays

[René Scharfe]

Convert calls of memcpy(3) to use COPY_ARRAY, which shortens and
simplifies the code a bit.

Patch generated by Coccinelle and contrib/coccinelle/array.cocci.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 fast-import.c | 2 +-
 kwset.c       | 2 +-
 packfile.c    | 6 +++---
 pretty.c      | 4 ++--
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index 76a7bd3699..6dfdd6801c 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -644,7 +644,7 @@ static struct tree_content *grow_tree_content(
 	struct tree_content *r = new_tree_content(t->entry_count + amt);
 	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);
 	release_tree_content(t);
 	return r;
 }
diff --git a/kwset.c b/kwset.c
index 4fb6455aca..090ffcafa2 100644
--- a/kwset.c
+++ b/kwset.c
@@ -475,7 +475,7 @@ kwsprep (kwset_t kws)
 	for (i = 0; i < NCHAR; ++i)
 	  kwset->next[i] = next[U(trans[i])];
       else
-	memcpy(kwset->next, next, NCHAR * sizeof(struct trie *));
+	COPY_ARRAY(kwset->next, next, NCHAR);
     }

   /* Fix things up for any translation table. */
diff --git a/packfile.c b/packfile.c
index d786ec7312..d55cb7f013 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1269,7 +1269,7 @@ static enum object_type packed_to_object_type(struct repository *r,
 		if (poi_stack_nr >= poi_stack_alloc && poi_stack == small_poi_stack) {
 			poi_stack_alloc = alloc_nr(poi_stack_nr);
 			ALLOC_ARRAY(poi_stack, poi_stack_alloc);
-			memcpy(poi_stack, small_poi_stack, sizeof(off_t)*poi_stack_nr);
+			COPY_ARRAY(poi_stack, small_poi_stack, poi_stack_nr);
 		} else {
 			ALLOC_GROW(poi_stack, poi_stack_nr+1, poi_stack_alloc);
 		}
@@ -1679,8 +1679,8 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 		    && delta_stack == small_delta_stack) {
 			delta_stack_alloc = alloc_nr(delta_stack_nr);
 			ALLOC_ARRAY(delta_stack, delta_stack_alloc);
-			memcpy(delta_stack, small_delta_stack,
-			       sizeof(*delta_stack)*delta_stack_nr);
+			COPY_ARRAY(delta_stack, small_delta_stack,
+				   delta_stack_nr);
 		} else {
 			ALLOC_GROW(delta_stack, delta_stack_nr+1, delta_stack_alloc);
 		}
diff --git a/pretty.c b/pretty.c
index ced0485257..e4ed14effe 100644
--- a/pretty.c
+++ b/pretty.c
@@ -106,8 +106,8 @@ static void setup_commit_formats(void)
 	commit_formats_len = ARRAY_SIZE(builtin_formats);
 	builtin_formats_len = commit_formats_len;
 	ALLOC_GROW(commit_formats, commit_formats_len, commit_formats_alloc);
-	memcpy(commit_formats, builtin_formats,
-	       sizeof(*builtin_formats)*ARRAY_SIZE(builtin_formats));
+	COPY_ARRAY(commit_formats, builtin_formats,
+		   ARRAY_SIZE(builtin_formats));

 	git_config(git_pretty_formats_config, NULL);
 }
--
2.22.0

Re: [PATCH 2/2] use COPY_ARRAY for copying arrays

[Derrick Stolee]

On 6/15/2019 2:36 PM, René Scharfe wrote:
> Convert calls of memcpy(3) to use COPY_ARRAY, which shortens and
> simplifies the code a bit.

These changes do look simpler. Thanks!

> Patch generated by Coccinelle and contrib/coccinelle/array.cocci.

And this auto-generation is particularly useful!

> 
> Signed-off-by: Rene Scharfe <l.s.r@web.de>
> ---
>  fast-import.c | 2 +-
>  kwset.c       | 2 +-
>  packfile.c    | 6 +++---
>  pretty.c      | 4 ++--
>  4 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/kwset.c b/kwset.c
> index 4fb6455aca..090ffcafa2 100644
> --- a/kwset.c
> +++ b/kwset.c
> @@ -475,7 +475,7 @@ kwsprep (kwset_t kws)
>  	for (i = 0; i < NCHAR; ++i)
>  	  kwset->next[i] = next[U(trans[i])];
>        else
> -	memcpy(kwset->next, next, NCHAR * sizeof(struct trie *));
> +	COPY_ARRAY(kwset->next, next, NCHAR);

I was unfamiliar with kwset.c, so I took a look and noticed that
it was adapted from GNU grep, so this change takes us even farther
from the original source (and closer to Git source conventions).

I think this is the right thing to do, but thought I'd point it
out in case anyone thought differently.

Both patches LGTM.

Thanks,
-Stolee