Re: [PATCH] mv: prevent mismatched data when ignoring errors.
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Mar 17, 2014, 06:33 UTC
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- <7vtxax2v1q.fsf@alter.siamese.dyndns.org>
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- <7v1ty14z8x.fsf@alter.siamese.dyndns.org>
Junio C Hamano <gitster@pobox.com> writes:
Show 6 quoted lines
> Would it make sense to go one step further to introduce two macros > to make this kind of screw-up less likely? > ... > After letting my eyes coast over hits from "git grep memmove", there > do seem to be some places that these would help readability, but not > very many.
I see quite a many hits that follow this pattern
memmove(array + pos, array + pos + 1, sizeof(*array) * (nr - pos))
to make a single slot in a middle of array available, which would be good candidates to use MOVE_DOWN(). Just to show a few:
builtin/mv.c:226: memmove(source + i, source + i + 1, builtin/mv.c-227- (argc - i) * sizeof(char *)); builtin/mv.c:228: memmove(destination + i, builtin/mv.c-229- destination + i + 1, builtin/mv.c-230- (argc - i) * sizeof(char *)); cache-tree.c:92: memmove(it->down + pos + 1, cache-tree.c-93- it->down + pos, cache-tree.c-94- sizeof(down) * (it->subtree_nr - pos - 1));
Perhaps something like this patch to start off; I am not sure MOVE_DOWN_BOUNDED is needed, though.
cache.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
diff --git a/cache.h b/cache.h index b66cb49..b2615ab 100644 --- a/cache.h +++ b/cache.h @@ -455,6 +455,39 @@ extern int daemonize(void); } \ } while (0) +/* + * With an array "array" that currently holds "nr" elements, move + * elements at "at" and later down by "count" elements to make room to + * add in new elements. The caller is responsible for making sure + * that the array has enough room to hold "nr" + "count" slots. + */ +#define MOVE_DOWN(array, nr, at, count) \ + memmove((array) + (at) + (count), \ + (array) + (at), \ + sizeof((array)[0]) * ((nr) - (at))) + +/* + * With an array "array" that has enough memory to hold "alloc" + * elements allocated and currently holds "nr" elements, move elements + * at "at" and later down by "count" elements to make room to add in + * new elements. + */ +#define MOVE_DOWN_BOUNDED(array, nr, at, count, alloc) \ + do { \ + if ((alloc) <= (nr) + (count)) \ + BUG("MOVE_DOWN beyond the end of an array"); \ + MOVE_DOWN((array), (nr), (at), (count)); \ + } while (0) + +/* + * With an array "array" that curently holds "nr" elements, move elements + * at "at" + "count" and later down by "count" elements, removing the + * elements between "at" and "at" + "count". + */ +#define MOVE_UP(array, nr, at, count) \ + memmove((array) + (at), (array) + (at) + (count), \ + sizeof((array)[0]) * ((nr) - ((at) + (count)))) + /* Initialize and use the cache information */ extern int read_index(struct index_state *); extern int read_index_preload(struct index_state *, const struct pathspec *pathspec);