On 10/4/2018 6:59 PM, René Scharfe wrote:
Am 01.10.2018 um 22:37 schrieb René Scharfe:
Am 01.10.2018 um 21:26 schrieb Derrick Stolee:
Good catch! I'm disappointed that we couldn't use type-checking here, as
it is quite difficult to discover that the types are wrong here.
Generics in C are hard, and type checking traditionally falls by the
wayside. You could use macros for that, like klib [*] does, but that
has its own downsides (more object text, debugging the sort macros
themselves is harder).
[*] https://github.com/attractivechaos/klib/blob/master/ksort.h
We could also do something like this to reduce the amount of manual
casting, but do we want to? (Macro at the bottom, three semi-random
examples at the top.)
I like the idea! It certainly can assist in some of the repeat work when
preparing to QSORT, and make it less error-prone.
---
bisect.c | 11 +++--------
commit-graph.c | 9 ++-------
commit-reach.c | 12 +++++-------
git-compat-util.h | 12 ++++++++++++
4 files changed, 22 insertions(+), 22 deletions(-)
diff --git a/bisect.c b/bisect.c
index e8b17cf7e1..06be3a3c15 100644
--- a/bisect.c
+++ b/bisect.c
@@ -192,16 +192,11 @@ struct commit_dist {
int distance;
};
-static int compare_commit_dist(const void *a_, const void *b_)
-{
- struct commit_dist *a, *b;
-
- a = (struct commit_dist *)a_;
- b = (struct commit_dist *)b_;
+DEFINE_SORT(sort_by_commit_dist, struct commit_dist, a, b, {
if (a->distance != b->distance)
return b->distance - a->distance; /* desc sort */
return oidcmp(&a->commit->object.oid, &b->commit->object.oid);
-}
+})
static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
{
@@ -223,7 +218,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
array[cnt].distance = distance;
cnt++;
}
- QSORT(array, cnt, compare_commit_dist);
+ sort_by_commit_dist(array, cnt);
for (p = list, i = 0; i < cnt; i++) {
struct object *obj = &(array[i].commit->object);
diff --git a/commit-graph.c b/commit-graph.c
index 7f4519ec3b..a2202414e0 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -550,12 +550,7 @@ static void write_graph_chunk_large_edges(struct hashfile *f,
}
}
-static int commit_compare(const void *_a, const void *_b)
-{
- const struct object_id *a = (const struct object_id *)_a;
- const struct object_id *b = (const struct object_id *)_b;
- return oidcmp(a, b);
-}
+DEFINE_SORT(sort_oids, struct object_id, a, b, return oidcmp(a, b))
struct packed_commit_list {
struct commit **list;
@@ -780,7 +775,7 @@ void write_commit_graph(const char *obj_dir,
close_reachable(&oids);
- QSORT(oids.list, oids.nr, commit_compare);
+ sort_oids(oids.list, oids.nr);
count_distinct = 1;
for (i = 1; i < oids.nr; i++) {
diff --git a/commit-reach.c b/commit-reach.c
index 2f5e592d16..3aef47c3dd 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -527,17 +527,15 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
return is_descendant_of(commit, list);
}
-static int compare_commits_by_gen(const void *_a, const void *_b)
-{
- const struct commit *a = *(const struct commit * const *)_a;
- const struct commit *b = *(const struct commit * const *)_b;
-
+DEFINE_SORT(sort_commits_by_gen, struct commit *, ap, bp, {
+ const struct commit *a = *ap;
+ const struct commit *b = *bp;
if (a->generation < b->generation)
return -1;
if (a->generation > b->generation)
return 1;
return 0;
-}
+})
Here, to make the macro version compile you need to cast ap and bp,
which gives us a level of type-safety that wasn't there before. That can
help us find errors at compile-time!
int can_all_from_reach_with_flag(struct object_array *from,
unsigned int with_flag,
@@ -580,7 +578,7 @@ int can_all_from_reach_with_flag(struct object_array *from,
nr_commits++;
}
- QSORT(list, nr_commits, compare_commits_by_gen);
+ sort_commits_by_gen(list, nr_commits);
for (i = 0; i < nr_commits; i++) {
/* DFS from list[i] */
diff --git a/git-compat-util.h b/git-compat-util.h
index 5f2e90932f..f9e78d69a2 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1066,6 +1066,18 @@ static inline void sane_qsort(void *base, size_t nmemb, size_t size,
qsort(base, nmemb, size, compar);
}
+#define DEFINE_SORT(name, elemtype, one, two, code) \
+static int name##_compare(const void *one##_v_, const void *two##_v_) \
+{ \
+ elemtype const *one = one##_v_; \
+ elemtype const *two = two##_v_; \
+ code; \
+} \
+static void name(elemtype *array, size_t n) \
+{ \
+ QSORT(array, n, name##_compare); \
+}
+
I would use this macro.
Thanks,
-Stolee
