Use the correct function definition for function pointers

Passing a function pointer with different parameters is UB, even if
those params are (void *). Use our separate `_cb` functions that will do
the correct casting.

src/libgit2/iterator.c

@@ -26,9 +26,10 @@
 #define iterator__ignore_dot_git(I)    iterator__flag(I,IGNORE_DOT_GIT)
 #define iterator__descend_symlinks(I)  iterator__flag(I,DESCEND_SYMLINKS)
 
-
 static void iterator_set_ignore_case(git_iterator *iter, bool ignore_case)
 {
+	int (*vector_cmp)(const void *a, const void *b);
+
 	if (ignore_case)
 		iter->flags |= GIT_ITERATOR_IGNORE_CASE;
 	else
@@ -39,7 +40,9 @@ static void iterator_set_ignore_case(git_iterator *iter, bool ignore_case)
 	iter->prefixcomp = ignore_case ? git__prefixcmp_icase : git__prefixcmp;
 	iter->entry_srch = ignore_case ? git_index_entry_isrch : git_index_entry_srch;
 
-	git_vector_set_cmp(&iter->pathlist, (git_vector_cmp)iter->strcomp);
+	vector_cmp = ignore_case ? git__strcasecmp_cb : git__strcmp_cb;
+
+	git_vector_set_cmp(&iter->pathlist, vector_cmp);
 }
 
 static int iterator_range_init(
@@ -299,6 +302,7 @@ typedef enum {
 static iterator_pathlist_search_t iterator_pathlist_search(
 	git_iterator *iter, const char *path, size_t path_len)
 {
+	int (*vector_cmp)(const void *a, const void *b);
 	const char *p;
 	size_t idx;
 	int error;
@@ -308,8 +312,10 @@ static iterator_pathlist_search_t iterator_pathlist_search(
 
 	git_vector_sort(&iter->pathlist);
 
-	error = git_vector_bsearch2(&idx, &iter->pathlist,
-		(git_vector_cmp)iter->strcomp, path);
+	vector_cmp = (iter->flags & GIT_ITERATOR_IGNORE_CASE) != 0 ?
+		git__strcasecmp_cb : git__strcmp_cb;
+
+	error = git_vector_bsearch2(&idx, &iter->pathlist, vector_cmp, path);
 
 	/* the given path was found in the pathlist.  since the pathlist only
 	 * matches directories when they're suffixed with a '/', analyze the

src/libgit2/refs.c

@@ -1080,6 +1080,12 @@ int git_reference_cmp(
 	return git_oid__cmp(&ref1->target.oid, &ref2->target.oid);
 }
 
+int git_reference__cmp_cb(const void *a, const void *b)
+{
+	return git_reference_cmp(
+		(const git_reference *)a, (const git_reference *)b);
+}
+
 /*
  * Starting with the reference given by `ref_name`, follows symbolic
  * references until a direct reference is found and updated the OID

src/libgit2/refs.h

@@ -92,6 +92,12 @@ int git_reference__is_tag(const char *ref_name);
 int git_reference__is_note(const char *ref_name);
 const char *git_reference__shorthand(const char *name);
 
+/*
+ * A `git_reference_cmp` wrapper suitable for passing to generic
+ * comparators, like `vector_cmp` / `tsort` / etc.
+ */
+int git_reference__cmp_cb(const void *a, const void *b);
+
 /**
  * Lookup a reference by name and try to resolve to an OID.
  *

tests/libgit2/iterator/workdir.c

@@ -585,9 +585,9 @@ void test_iterator_workdir__filesystem(void)
 	expect_iterator_items(i, 5, expect_noauto, 18, expect_trees);
 	git_iterator_free(i);
 
-	git__tsort((void **)expect_base, 8, (git__tsort_cmp)git__strcasecmp);
-	git__tsort((void **)expect_trees, 18, (git__tsort_cmp)git__strcasecmp);
-	git__tsort((void **)expect_noauto, 5, (git__tsort_cmp)git__strcasecmp);
+	git__tsort((void **)expect_base, 8, git__strcasecmp_cb);
+	git__tsort((void **)expect_trees, 18, git__strcasecmp_cb);
+	git__tsort((void **)expect_noauto, 5, git__strcasecmp_cb);
 
 	i_opts.flags = GIT_ITERATOR_IGNORE_CASE;
 	cl_git_pass(git_iterator_for_filesystem(&i, "status/subdir", &i_opts));

tests/libgit2/network/remote/rename.c

@@ -216,7 +216,7 @@ void test_network_remote_rename__symref_head(void)
 	cl_assert_equal_i(0, problems.count);
 	git_strarray_dispose(&problems);
 
-	cl_git_pass(git_vector_init(&refs, 2, (git_vector_cmp) git_reference_cmp));
+	cl_git_pass(git_vector_init(&refs, 2, git_reference__cmp_cb));
 	cl_git_pass(git_branch_iterator_new(&iter, _repo, GIT_BRANCH_REMOTE));
 
 	while ((error = git_branch_next(&ref, &btype, iter)) == 0) {

tests/libgit2/odb/sorting.c

@@ -7,6 +7,11 @@ typedef struct {
 	size_t position;
 } fake_backend;
 
+static void odb_backend_free(git_odb_backend *odb)
+{
+	git__free(odb);
+}
+
 static git_odb_backend *new_backend(size_t position)
 {
 	fake_backend *b;
@@ -15,7 +20,7 @@ static git_odb_backend *new_backend(size_t position)
 	if (b == NULL)
 		return NULL;
 
-	b->base.free = (void (*)(git_odb_backend *)) git__free;
+	b->base.free = odb_backend_free;
 	b->base.version = GIT_ODB_BACKEND_VERSION;
 	b->position = position;
 	return (git_odb_backend *)b;