diff --git a/apply.c b/apply.c
index 2b7cd930ef..6b4dbe0c88 100644
--- a/apply.c
+++ b/apply.c
@@ -125,7 +125,7 @@ void clear_apply_state(struct apply_state *state)
 	/* &state->fn_table is cleared at the end of apply_patch() */
 }
 
-static void mute_routine(const char *msg, va_list params)
+static void mute_routine(const char *msg UNUSED, va_list params UNUSED)
 {
 	/* do nothing */
 }
@@ -892,9 +892,9 @@ static int parse_traditional_patch(struct apply_state *state,
 	return 0;
 }
 
-static int gitdiff_hdrend(struct gitdiff_data *state,
-			  const char *line,
-			  struct patch *patch)
+static int gitdiff_hdrend(struct gitdiff_data *state UNUSED,
+			  const char *line UNUSED,
+			  struct patch *patch UNUSED)
 {
 	return 1;
 }
@@ -1044,7 +1044,7 @@ static int gitdiff_renamedst(struct gitdiff_data *state,
 	return 0;
 }
 
-static int gitdiff_similarity(struct gitdiff_data *state,
+static int gitdiff_similarity(struct gitdiff_data *state UNUSED,
 			      const char *line,
 			      struct patch *patch)
 {
@@ -1054,7 +1054,7 @@ static int gitdiff_similarity(struct gitdiff_data *state,
 	return 0;
 }
 
-static int gitdiff_dissimilarity(struct gitdiff_data *state,
+static int gitdiff_dissimilarity(struct gitdiff_data *state UNUSED,
 				 const char *line,
 				 struct patch *patch)
 {
@@ -1104,9 +1104,9 @@ static int gitdiff_index(struct gitdiff_data *state,
  * This is normal for a diff that doesn't change anything: we'll fall through
  * into the next diff. Tell the parser to break out.
  */
-static int gitdiff_unrecognized(struct gitdiff_data *state,
-				const char *line,
-				struct patch *patch)
+static int gitdiff_unrecognized(struct gitdiff_data *state UNUSED,
+				const char *line UNUSED,
+				struct patch *patch UNUSED)
 {
 	return 1;
 }
diff --git a/archive.c b/archive.c
index cc1087262f..941495f5d7 100644
--- a/archive.c
+++ b/archive.c
@@ -498,7 +498,7 @@ static void parse_treeish_arg(const char **argv,
 	ar_args->time = archive_time;
 }
 
-static void extra_file_info_clear(void *util, const char *str)
+static void extra_file_info_clear(void *util, const char *str UNUSED)
 {
 	struct extra_file_info *info = util;
 	free(info->base);
diff --git a/builtin/gc.c b/builtin/gc.c
index 243ee85d28..24ea85c7af 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -322,7 +322,7 @@ static uint64_t estimate_repack_memory(struct packed_git *pack)
 	return os_cache + heap;
 }
 
-static int keep_one_pack(struct string_list_item *item, void *data)
+static int keep_one_pack(struct string_list_item *item, void *data UNUSED)
 {
 	strvec_pushf(&repack, "--keep-pack=%s", basename(item->string));
 	return 0;
diff --git a/builtin/remote.c b/builtin/remote.c
index 910f7b9316..93285fc06e 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -942,7 +942,7 @@ static int rm(int argc, const char **argv, const char *prefix)
 	return result;
 }
 
-static void clear_push_info(void *util, const char *string)
+static void clear_push_info(void *util, const char *string UNUSED)
 {
 	struct push_info *info = util;
 	free(info->dest);
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 0b4acb442b..1e29a3d7dc 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -181,7 +181,7 @@ static void module_list_release(struct module_list *ml)
 	free(ml->entries);
 }
 
-static int module_list_compute(int argc, const char **argv,
+static int module_list_compute(const char **argv,
 			       const char *prefix,
 			       struct pathspec *pathspec,
 			       struct module_list *list)
@@ -405,7 +405,7 @@ static int module_foreach(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_foreach_options,
 			     git_submodule_helper_usage, 0);
 
-	if (module_list_compute(0, NULL, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(NULL, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	info.argc = argc;
@@ -545,7 +545,7 @@ static int module_init(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_init_options,
 			     git_submodule_helper_usage, 0);
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(argv, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	/*
@@ -732,7 +732,7 @@ static int module_status(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_status_options,
 			     git_submodule_helper_usage, 0);
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(argv, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	info.prefix = prefix;
@@ -1326,7 +1326,7 @@ static int module_sync(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_sync_options,
 			     git_submodule_helper_usage, 0);
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(argv, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	info.prefix = prefix;
@@ -1479,7 +1479,7 @@ static int module_deinit(int argc, const char **argv, const char *prefix)
 	if (!argc && !all)
 		die(_("Use '--all' if you really want to deinitialize all submodules"));
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(argv, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	info.prefix = prefix;
@@ -2697,7 +2697,7 @@ static int module_update(int argc, const char **argv, const char *prefix)
 	if (opt.update_default)
 		opt.update_strategy.type = opt.update_default;
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &opt.list) < 0) {
+	if (module_list_compute(argv, prefix, &pathspec, &opt.list) < 0) {
 		ret = 1;
 		goto cleanup;
 	}
@@ -2709,7 +2709,7 @@ static int module_update(int argc, const char **argv, const char *prefix)
 		struct module_list list = MODULE_LIST_INIT;
 		struct init_cb info = INIT_CB_INIT;
 
-		if (module_list_compute(argc, argv, opt.prefix,
+		if (module_list_compute(argv, opt.prefix,
 					&pathspec2, &list) < 0) {
 			module_list_release(&list);
 			ret = 1;
@@ -2840,7 +2840,7 @@ static int absorb_git_dirs(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, embed_gitdir_options,
 			     git_submodule_helper_usage, 0);
 
-	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
+	if (module_list_compute(argv, prefix, &pathspec, &list) < 0)
 		goto cleanup;
 
 	for (i = 0; i < list.nr; i++)
diff --git a/builtin/update-index.c b/builtin/update-index.c
index b62249905f..7b0c924d7d 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -732,7 +732,7 @@ static int do_unresolve(int ac, const char **av,
 	return err;
 }
 
-static int do_reupdate(int ac, const char **av,
+static int do_reupdate(const char **paths,
 		       const char *prefix)
 {
 	/* Read HEAD and run update-index on paths that are
@@ -744,7 +744,7 @@ static int do_reupdate(int ac, const char **av,
 
 	parse_pathspec(&pathspec, 0,
 		       PATHSPEC_PREFER_CWD,
-		       prefix, av + 1);
+		       prefix, paths);
 
 	if (read_ref("HEAD", &head_oid))
 		/* If there is no HEAD, that means it is an initial
@@ -970,7 +970,7 @@ static enum parse_opt_result reupdate_callback(
 
 	/* consume remaining arguments. */
 	setup_work_tree();
-	*has_errors = do_reupdate(ctx->argc, ctx->argv, prefix);
+	*has_errors = do_reupdate(ctx->argv + 1, prefix);
 	if (*has_errors)
 		active_cache_changed = 0;
 
diff --git a/compat/nonblock.c b/compat/nonblock.c
index 9694ebdb1d..5b51195c32 100644
--- a/compat/nonblock.c
+++ b/compat/nonblock.c
@@ -41,7 +41,7 @@ int enable_pipe_nonblock(int fd)
 
 #else
 
-int enable_pipe_nonblock(int fd)
+int enable_pipe_nonblock(int fd UNUSED)
 {
 	errno = ENOSYS;
 	return -1;
diff --git a/convert.c b/convert.c
index 95e6a5244f..9b67649032 100644
--- a/convert.c
+++ b/convert.c
@@ -1549,7 +1549,7 @@ struct stream_filter {
 	struct stream_filter_vtbl *vtbl;
 };
 
-static int null_filter_fn(struct stream_filter *filter,
+static int null_filter_fn(struct stream_filter *filter UNUSED,
 			  const char *input, size_t *isize_p,
 			  char *output, size_t *osize_p)
 {
@@ -1568,7 +1568,7 @@ static int null_filter_fn(struct stream_filter *filter,
 	return 0;
 }
 
-static void null_free_fn(struct stream_filter *filter)
+static void null_free_fn(struct stream_filter *filter UNUSED)
 {
 	; /* nothing -- null instances are shared */
 }
diff --git a/date.c b/date.c
index 68a260c214..53bd6a7932 100644
--- a/date.c
+++ b/date.c
@@ -1101,7 +1101,7 @@ static void date_tea(struct tm *tm, struct tm *now, int *num)
 	date_time(tm, now, 17);
 }
 
-static void date_pm(struct tm *tm, struct tm *now, int *num)
+static void date_pm(struct tm *tm, struct tm *now UNUSED, int *num)
 {
 	int hour, n = *num;
 	*num = 0;
@@ -1115,7 +1115,7 @@ static void date_pm(struct tm *tm, struct tm *now, int *num)
 	tm->tm_hour = (hour % 12) + 12;
 }
 
-static void date_am(struct tm *tm, struct tm *now, int *num)
+static void date_am(struct tm *tm, struct tm *now UNUSED, int *num)
 {
 	int hour, n = *num;
 	*num = 0;
@@ -1129,7 +1129,7 @@ static void date_am(struct tm *tm, struct tm *now, int *num)
 	tm->tm_hour = (hour % 12);
 }
 
-static void date_never(struct tm *tm, struct tm *now, int *num)
+static void date_never(struct tm *tm, struct tm *now UNUSED, int *num)
 {
 	time_t n = 0;
 	localtime_r(&n, tm);
diff --git a/diff.c b/diff.c
index 648f6717a5..bba888a34a 100644
--- a/diff.c
+++ b/diff.c
@@ -2488,6 +2488,9 @@ static int diffstat_consume(void *priv, char *line, unsigned long len)
 	struct diffstat_t *diffstat = priv;
 	struct diffstat_file *x = diffstat->files[diffstat->nr - 1];
 
+	if (!len)
+		BUG("xdiff fed us an empty line");
+
 	if (line[0] == '+')
 		x->added++;
 	else if (line[0] == '-')
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index c88e50c632..03fcbcb40b 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -38,7 +38,7 @@ static int diffgrep_consume(void *priv, char *line, unsigned long len)
 
 static int diff_grep(mmfile_t *one, mmfile_t *two,
 		     struct diff_options *o,
-		     regex_t *regexp, kwset_t kws)
+		     regex_t *regexp, kwset_t kws UNUSED)
 {
 	struct diffgrep_cb ecbdata;
 	xpparam_t xpp;
@@ -114,7 +114,7 @@ static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws,
 }
 
 static int has_changes(mmfile_t *one, mmfile_t *two,
-		       struct diff_options *o,
+		       struct diff_options *o UNUSED,
 		       regex_t *regexp, kwset_t kws)
 {
 	unsigned int c1 = one ? contains(one, regexp, kws, 0) : 0;
diff --git a/exec-cmd.c b/exec-cmd.c
index eeb2ee52b8..0232bbc990 100644
--- a/exec-cmd.c
+++ b/exec-cmd.c
@@ -252,7 +252,7 @@ static const char *system_prefix(void)
  * This is called during initialization, but No work needs to be done here when
  * runtime prefix is not being used.
  */
-void git_resolve_executable_dir(const char *argv0)
+void git_resolve_executable_dir(const char *argv0 UNUSED)
 {
 }
 
diff --git a/git-compat-util.h b/git-compat-util.h
index ea53ea4a78..a76d0526f7 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -314,7 +314,9 @@ typedef unsigned long uintptr_t;
 #ifdef PRECOMPOSE_UNICODE
 #include "compat/precompose_utf8.h"
 #else
-static inline const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix)
+static inline const char *precompose_argv_prefix(int argc UNUSED,
+						 const char **argv UNUSED,
+						 const char *prefix)
 {
 	return prefix;
 }
@@ -339,7 +341,9 @@ struct itimerval {
 #endif
 
 #ifdef NO_SETITIMER
-static inline int setitimer(int which, const struct itimerval *value, struct itimerval *newvalue) {
+static inline int setitimer(int which UNUSED,
+			    const struct itimerval *value UNUSED,
+			    struct itimerval *newvalue UNUSED) {
 	return 0; /* pretend success */
 }
 #endif
@@ -424,7 +428,7 @@ int lstat_cache_aware_rmdir(const char *path);
 #endif
 
 #ifndef has_dos_drive_prefix
-static inline int git_has_dos_drive_prefix(const char *path)
+static inline int git_has_dos_drive_prefix(const char *path UNUSED)
 {
 	return 0;
 }
@@ -432,7 +436,7 @@ static inline int git_has_dos_drive_prefix(const char *path)
 #endif
 
 #ifndef skip_dos_drive_prefix
-static inline int git_skip_dos_drive_prefix(char **path)
+static inline int git_skip_dos_drive_prefix(char **path UNUSED)
 {
 	return 0;
 }
@@ -1467,11 +1471,11 @@ int open_nofollow(const char *path, int flags);
 #endif
 
 #ifndef _POSIX_THREAD_SAFE_FUNCTIONS
-static inline void flockfile(FILE *fh)
+static inline void flockfile(FILE *fh UNUSED)
 {
 	; /* nothing */
 }
-static inline void funlockfile(FILE *fh)
+static inline void funlockfile(FILE *fh UNUSED)
 {
 	; /* nothing */
 }
diff --git a/ll-merge.c b/ll-merge.c
index 8955d7e1f6..a8e2db9336 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -49,14 +49,14 @@ void reset_merge_attributes(void)
 /*
  * Built-in low-levels
  */
-static enum ll_merge_result ll_binary_merge(const struct ll_merge_driver *drv_unused,
+static enum ll_merge_result ll_binary_merge(const struct ll_merge_driver *drv UNUSED,
 			   mmbuffer_t *result,
-			   const char *path,
-			   mmfile_t *orig, const char *orig_name,
-			   mmfile_t *src1, const char *name1,
-			   mmfile_t *src2, const char *name2,
+			   const char *path UNUSED,
+			   mmfile_t *orig, const char *orig_name UNUSED,
+			   mmfile_t *src1, const char *name1 UNUSED,
+			   mmfile_t *src2, const char *name2 UNUSED,
 			   const struct ll_merge_options *opts,
-			   int marker_size)
+			   int marker_size UNUSED)
 {
 	enum ll_merge_result ret;
 	mmfile_t *stolen;
@@ -183,9 +183,9 @@ static void create_temp(mmfile_t *src, char *path, size_t len)
 static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 			mmbuffer_t *result,
 			const char *path,
-			mmfile_t *orig, const char *orig_name,
-			mmfile_t *src1, const char *name1,
-			mmfile_t *src2, const char *name2,
+			mmfile_t *orig, const char *orig_name UNUSED,
+			mmfile_t *src1, const char *name1 UNUSED,
+			mmfile_t *src2, const char *name2 UNUSED,
 			const struct ll_merge_options *opts,
 			int marker_size)
 {
diff --git a/merge-ort.c b/merge-ort.c
index e5f41cce48..7e83ebfaa9 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -397,7 +397,7 @@ struct conflicted_submodule_item {
 	int flag;
 };
 
-static void conflicted_submodule_item_free(void *util, const char *str)
+static void conflicted_submodule_item_free(void *util, const char *str UNUSED)
 {
 	struct conflicted_submodule_item *item = util;
 
diff --git a/object-file.c b/object-file.c
index 5e30960234..957790098f 100644
--- a/object-file.c
+++ b/object-file.c
@@ -140,27 +140,32 @@ static void git_hash_sha256_final_oid(struct object_id *oid, git_hash_ctx *ctx)
 	oid->algo = GIT_HASH_SHA256;
 }
 
-static void git_hash_unknown_init(git_hash_ctx *ctx)
+static void git_hash_unknown_init(git_hash_ctx *ctx UNUSED)
 {
 	BUG("trying to init unknown hash");
 }
 
-static void git_hash_unknown_clone(git_hash_ctx *dst, const git_hash_ctx *src)
+static void git_hash_unknown_clone(git_hash_ctx *dst UNUSED,
+				   const git_hash_ctx *src UNUSED)
 {
 	BUG("trying to clone unknown hash");
 }
 
-static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
+static void git_hash_unknown_update(git_hash_ctx *ctx UNUSED,
+				    const void *data UNUSED,
+				    size_t len UNUSED)
 {
 	BUG("trying to update unknown hash");
 }
 
-static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
+static void git_hash_unknown_final(unsigned char *hash UNUSED,
+				   git_hash_ctx *ctx UNUSED)
 {
 	BUG("trying to finalize unknown hash");
 }
 
-static void git_hash_unknown_final_oid(struct object_id *oid, git_hash_ctx *ctx)
+static void git_hash_unknown_final_oid(struct object_id *oid UNUSED,
+				       git_hash_ctx *ctx UNUSED)
 {
 	BUG("trying to finalize unknown hash");
 }
diff --git a/reflog-walk.c b/reflog-walk.c
index 7aa6595a51..8a4d8fa3bd 100644
--- a/reflog-walk.c
+++ b/reflog-walk.c
@@ -55,7 +55,7 @@ static void free_complete_reflog(struct complete_reflogs *array)
 	free(array);
 }
 
-static void complete_reflogs_clear(void *util, const char *str)
+static void complete_reflogs_clear(void *util, const char *str UNUSED)
 {
 	struct complete_reflogs *array = util;
 	free_complete_reflog(array);
diff --git a/string-list.c b/string-list.c
index 549fc416d6..42bacaec55 100644
--- a/string-list.c
+++ b/string-list.c
@@ -156,7 +156,7 @@ void filter_string_list(struct string_list *list, int free_util,
 	list->nr = dst;
 }
 
-static int item_is_not_empty(struct string_list_item *item, void *unused)
+static int item_is_not_empty(struct string_list_item *item, void *data UNUSED)
 {
 	return *item->string != '\0';
 }
diff --git a/t/helper/test-path-utils.c b/t/helper/test-path-utils.c
index d20e1b7a18..f69709d674 100644
--- a/t/helper/test-path-utils.c
+++ b/t/helper/test-path-utils.c
@@ -8,7 +8,8 @@
  * GIT_CEILING_DIRECTORIES.  If the path is unusable for some reason,
  * die with an explanation.
  */
-static int normalize_ceiling_entry(struct string_list_item *item, void *unused)
+static int normalize_ceiling_entry(struct string_list_item *item,
+				   void *data UNUSED)
 {
 	char *ceil = item->string;