Am 14.11.19 um 14:15 schrieb Markus Elfring:
> You mentioned “failures”. - I became curious then if corresponding software
> development challenges can be clarified a bit more.
Let's try to restore/repeat the pertinent paragraph, with context and
attribution:
Am 13.11.19 um 03:11 schrieb Junio C Hamano:
> René Scharfe <l.s.r@xxxxxx> writes:
>> Am 12.11.19 um 16:08 schrieb Markus Elfring:
>>>
>>> Do you find the following code variant (for the semantic patch language) also useful?
>>>
>>> memcpy(
>>> ( ptr, E, n *
>>> - sizeof(*(ptr))
>>> + sizeof(T)
>>> | arr, E, n *
>>> - sizeof(*(arr))
>>> + sizeof(T)
>>> | E, ptr, n *
>>> - sizeof(*(ptr))
>>> + sizeof(T)
>>> | E, arr, n *
>>> - sizeof(*(arr))
>>> + sizeof(T)
>>> )
>>> )
>
>> This reduces duplication in the semantic patch, which is nice. I think
>> I tried something like that at the time, but found that it failed to
>> produce some of the cases in 921d49be86 ("use COPY_ARRAY for copying
>> arrays", 2019-06-15) for some reason.
> Thanks for mentioning.
>
> I too recall that seemingly redundant entries were noticed during
> the review and at least back then removing the seemingly redundant
> ones caused failures in rewriting.
You can see for yourself by:
1. applying the patch at the bottom to implement your suggested change,
2. running "git show 921d49be86 | patch -p1 -R" to undo 921d49be86,
3. running "make contrib/coccinelle/array.cocci.patch",
4. running "patch -p1 <contrib/coccinelle/array.cocci.patch",
5. running "git diff".
If the new version of array.cocci is equivalent to the current one then
that last step should show no difference. For me, "git diff --stat"
reports, however:
contrib/coccinelle/array.cocci | 30 ++++++++++++++----------------
fast-import.c | 2 +-
packfile.c | 4 ++--
pretty.c | 4 ++--
4 files changed, 19 insertions(+), 21 deletions(-)
The changes in array.cocci are expected of course, but the others
indicate that the new version missed transformations that the current
version generated.
René
-- >8 --
diff --git a/contrib/coccinelle/array.cocci b/contrib/coccinelle/array.cocci
index 46b8d2ee11..e7bcbefcc1 100644
--- a/contrib/coccinelle/array.cocci
+++ b/contrib/coccinelle/array.cocci
@@ -12,27 +12,25 @@ T *ptr;
T[] arr;
expression E, n;
@@
+ memcpy(
(
- memcpy(ptr, E,
-- n * sizeof(*(ptr))
-+ n * sizeof(T)
- )
+ ptr, E, n *
+- sizeof(*(ptr))
++ sizeof(T)
|
- memcpy(arr, E,
-- n * sizeof(*(arr))
-+ n * sizeof(T)
- )
+ arr, E, n *
+- sizeof(*(arr))
++ sizeof(T)
|
- memcpy(E, ptr,
-- n * sizeof(*(ptr))
-+ n * sizeof(T)
- )
+ E, ptr, n *
+- sizeof(*(ptr))
++ sizeof(T)
|
- memcpy(E, arr,
-- n * sizeof(*(arr))
-+ n * sizeof(T)
- )
+ E, arr, n *
+- sizeof(*(arr))
++ sizeof(T)
)
+ )
@@
type T;
