hashmap_for_each_entry(): work around MSVC's run-time check failure #3

When compiling Git in Visual C, we do not have the luxury of
support for `typeof()`, and therefore `OFFSETOF_VAR()` unfortunately
has to fall back to pointer arithmetic.

When compiling code using the `hashmap_for_each_entry()` macro in Debug
mode, this leads to the "run-time check failure #3" because the variable
passed as `var` are not initialized, yet we calculate the pointer
difference `&(var->member)-var`.

This "run-time check failure" causes a scary dialog to pop up.

Work around this by initializing the respective variables.

Note: according to the C standard, performing pointer arithmetic
with `NULL` is not exactly well-defined, but it seems to work
here, and it is at least better than performing pointer arithmetic
with an uninitialized pointer.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

attr.c

@@ -160,7 +160,7 @@ static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
 	 * field and fill each entry with its corresponding git_attr.
 	 */
 	if (size != check->all_attrs_nr) {
-		struct attr_hash_entry *e;
+		struct attr_hash_entry *e = NULL;
 		struct hashmap_iter iter;
 
 		REALLOC_ARRAY(check->all_attrs, size);

blame.c

@@ -450,7 +450,7 @@ static int fingerprint_similarity(struct fingerprint *a, struct fingerprint *b)
 {
 	int intersection = 0;
 	struct hashmap_iter iter;
-	const struct fingerprint_entry *entry_a, *entry_b;
+	const struct fingerprint_entry *entry_a, *entry_b = NULL;
 
 	hashmap_for_each_entry(&b->map, &iter, entry_b,
 				entry /* member name */) {
@@ -469,7 +469,7 @@ static void fingerprint_subtract(struct fingerprint *a, struct fingerprint *b)
 {
 	struct hashmap_iter iter;
 	struct fingerprint_entry *entry_a;
-	const struct fingerprint_entry *entry_b;
+	const struct fingerprint_entry *entry_b = NULL;
 
 	hashmap_iter_init(&b->map, &iter);
 

bloom.c

@@ -221,7 +221,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
 
 	if (diffopt.num_changes <= max_changes) {
 		struct hashmap pathmap;
-		struct pathmap_hash_entry *e;
+		struct pathmap_hash_entry *e = NULL;
 		struct hashmap_iter iter;
 		hashmap_init(&pathmap, pathmap_cmp, NULL, 0);
 

builtin/describe.c

@@ -332,7 +332,7 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 	if (!have_util) {
 		struct hashmap_iter iter;
 		struct commit *c;
-		struct commit_name *n;
+		struct commit_name *n = NULL;
 
 		init_commit_names(&commit_names);
 		hashmap_for_each_entry(&names, &iter, n,

builtin/difftool.c

@@ -344,7 +344,7 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	FILE *fp;
 	struct hashmap working_tree_dups, submodules, symlinks2;
 	struct hashmap_iter iter;
-	struct pair_entry *entry;
+	struct pair_entry *entry = NULL;
 	struct index_state wtindex;
 	struct checkout lstate, rstate;
 	int rc, flags = RUN_GIT_CMD, err = 0;

builtin/fast-import.c

@@ -498,7 +498,7 @@ static void invalidate_pack_id(unsigned int id)
 	unsigned long lu;
 	struct tag *t;
 	struct hashmap_iter iter;
-	struct object_entry *e;
+	struct object_entry *e = NULL;
 
 	hashmap_for_each_entry(&object_table, &iter, e, ent) {
 		if (e->pack_id == id)

builtin/sparse-checkout.c

@@ -67,7 +67,7 @@ static int sparse_checkout_list(int argc, const char **argv)
 
 	if (pl.use_cone_patterns) {
 		int i;
-		struct pattern_entry *pe;
+		struct pattern_entry *pe = NULL;
 		struct hashmap_iter iter;
 		struct string_list sl = STRING_LIST_INIT_DUP;
 
@@ -153,7 +153,7 @@ static char *escaped_pattern(char *pattern)
 static void write_cone_to_file(FILE *fp, struct pattern_list *pl)
 {
 	int i;
-	struct pattern_entry *pe;
+	struct pattern_entry *pe = NULL;
 	struct hashmap_iter iter;
 	struct string_list sl = STRING_LIST_INIT_DUP;
 	struct strbuf parent_pattern = STRBUF_INIT;
@@ -465,7 +465,7 @@ static void add_patterns_cone_mode(int argc, const char **argv,
 				   struct pattern_list *pl)
 {
 	struct strbuf buffer = STRBUF_INIT;
-	struct pattern_entry *pe;
+	struct pattern_entry *pe = NULL;
 	struct hashmap_iter iter;
 	struct pattern_list existing;
 	char *sparse_filename = get_sparse_checkout_filename();

config.c

@@ -1953,7 +1953,7 @@ void git_configset_init(struct config_set *cs)
 
 void git_configset_clear(struct config_set *cs)
 {
-	struct config_set_element *entry;
+	struct config_set_element *entry = NULL;
 	struct hashmap_iter iter;
 	if (!cs->hash_initialized)
 		return;

merge-recursive.c

@@ -2151,8 +2151,8 @@ static void handle_directory_level_conflicts(struct merge_options *opt,
 					     struct tree *merge)
 {
 	struct hashmap_iter iter;
-	struct dir_rename_entry *head_ent;
-	struct dir_rename_entry *merge_ent;
+	struct dir_rename_entry *head_ent = NULL;
+	struct dir_rename_entry *merge_ent = NULL;
 
 	struct string_list remove_from_head = STRING_LIST_INIT_NODUP;
 	struct string_list remove_from_merge = STRING_LIST_INIT_NODUP;
@@ -2221,7 +2221,7 @@ static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
 {
 	struct hashmap *dir_renames;
 	struct hashmap_iter iter;
-	struct dir_rename_entry *entry;
+	struct dir_rename_entry *entry = NULL;
 	int i;
 
 	/*
@@ -2590,7 +2590,7 @@ static struct string_list *get_renames(struct merge_options *opt,
 	int i;
 	struct hashmap collisions;
 	struct hashmap_iter iter;
-	struct collision_entry *e;
+	struct collision_entry *e = NULL;
 	struct string_list *renames;
 
 	compute_collisions(&collisions, dir_renames, pairs);
@@ -2862,7 +2862,7 @@ static void initial_cleanup_rename(struct diff_queue_struct *pairs,
 				   struct hashmap *dir_renames)
 {
 	struct hashmap_iter iter;
-	struct dir_rename_entry *e;
+	struct dir_rename_entry *e = NULL;
 
 	hashmap_for_each_entry(dir_renames, &iter, e,
 				ent /* member name */) {

name-hash.c

@@ -706,7 +706,7 @@ void adjust_dirname_case(struct index_state *istate, char *name)
 
 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 {
-	struct cache_entry *ce;
+	struct cache_entry *ce = NULL;
 	unsigned int hash = memihash(name, namelen);
 
 	lazy_init_name_hash(istate);

revision.c

@@ -132,7 +132,7 @@ static void paths_and_oids_init(struct hashmap *map)
 static void paths_and_oids_clear(struct hashmap *map)
 {
 	struct hashmap_iter iter;
-	struct path_and_oids_entry *entry;
+	struct path_and_oids_entry *entry = NULL;
 
 	hashmap_for_each_entry(map, &iter, entry, ent /* member name */) {
 		oidset_clear(&entry->trees);
@@ -215,7 +215,7 @@ void mark_trees_uninteresting_sparse(struct repository *r,
 	unsigned has_interesting = 0, has_uninteresting = 0;
 	struct hashmap map;
 	struct hashmap_iter map_iter;
-	struct path_and_oids_entry *entry;
+	struct path_and_oids_entry *entry = NULL;
 	struct object_id *oid;
 	struct oidset_iter iter;
 

submodule-config.c

@@ -89,7 +89,7 @@ static void free_one_config(struct submodule_entry *entry)
 static void submodule_cache_clear(struct submodule_cache *cache)
 {
 	struct hashmap_iter iter;
-	struct submodule_entry *entry;
+	struct submodule_entry *entry = NULL;
 
 	if (!cache->initialized)
 		return;

t/helper/test-hashmap.c

@@ -162,7 +162,7 @@ int cmd__hashmap(int argc, const char **argv)
 	while (strbuf_getline(&line, stdin) != EOF) {
 		char *cmd, *p1 = NULL, *p2 = NULL;
 		unsigned int hash = 0;
-		struct test_entry *entry;
+		struct test_entry *entry = NULL;
 
 		/* break line into command and up to two parameters */
 		cmd = strtok(line.buf, DELIM);

t/helper/test-lazy-init-name-hash.c

@@ -29,8 +29,8 @@ static void dump_run(void)
 		char name[FLEX_ARRAY];
 	};
 
-	struct dir_entry *dir;
-	struct cache_entry *ce;
+	struct dir_entry *dir = NULL;
+	struct cache_entry *ce = NULL;
 
 	read_cache();
 	if (single) {