From: Derrick Stolee Date: Fri, 05 Oct 2018 12:15:09 GMT Subject: Re: [PATCH 15/16] commit-reach: make can_all_from_reach... linear Message-ID: In-Reply-To: <7b95417a-c8fb-4f1e-cb09-c36804a3a4d0@web.de> 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