diff --git a/src/change.h b/src/change.h
index a0d08f18..c29ee20f 100644
--- a/src/change.h
+++ b/src/change.h
@@ -31,9 +31,9 @@ void end_change_chain(View *view) NONNULL_ARGS;
 bool undo(View *view) NONNULL_ARGS WARN_UNUSED_RESULT;
 bool redo(View *view, unsigned long change_id) NONNULL_ARGS WARN_UNUSED_RESULT;
 void free_changes(Change *c) NONNULL_ARGS;
-void buffer_insert_bytes(View *view, const char *buf, size_t len) NONNULL_ARG(1);
+void buffer_insert_bytes(View *view, const char *buf, size_t len) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 void buffer_delete_bytes(View *view, size_t len) NONNULL_ARGS;
 void buffer_erase_bytes(View *view, size_t len) NONNULL_ARGS;
-void buffer_replace_bytes(View *view, size_t del_count, const char *ins, size_t ins_count) NONNULL_ARG(1);
+void buffer_replace_bytes(View *view, size_t del_count, const char *ins, size_t ins_count) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(3, 4);
 
 #endif
diff --git a/src/command/macro.h b/src/command/macro.h
index 0f4b04d6..fbbcb2ec 100644
--- a/src/command/macro.h
+++ b/src/command/macro.h
@@ -26,7 +26,7 @@ bool macro_cancel(MacroRecorder *m) WARN_UNUSED_RESULT NONNULL_ARGS;
 void macro_command_hook(MacroRecorder *m, const char *cmd_name, char **args) NONNULL_ARGS;
 void macro_search_hook(MacroRecorder *m, const char *pattern, bool reverse, bool add_to_history) NONNULL_ARG(1);
 void macro_insert_char_hook(MacroRecorder *m, CodePoint c) NONNULL_ARGS;
-void macro_insert_text_hook(MacroRecorder *m, const char *text, size_t size) NONNULL_ARG(1);
+void macro_insert_text_hook(MacroRecorder *m, const char *text, size_t size) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 String dump_macro(const MacroRecorder *m) WARN_UNUSED_RESULT NONNULL_ARGS;
 void free_macro(MacroRecorder *m) NONNULL_ARGS;
 
diff --git a/src/command/parse.h b/src/command/parse.h
index e18819c8..580e6d7a 100644
--- a/src/command/parse.h
+++ b/src/command/parse.h
@@ -13,7 +13,7 @@ typedef enum {
     CMDERR_UNEXPECTED_EOF,
 } CommandParseError;
 
-char *parse_command_arg(const CommandRunner *runner, const char *cmd, size_t len) NONNULL_ARG(1) RETURNS_NONNULL;
+char *parse_command_arg(const CommandRunner *runner, const char *cmd, size_t len) RETURNS_NONNULL NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 size_t find_end(const char *cmd, size_t pos, CommandParseError *err) NONNULL_ARGS;
 CommandParseError parse_commands(const CommandRunner *runner, PointerArray *array, const char *cmd) NONNULL_ARGS WARN_UNUSED_RESULT;
 const char *command_parse_error_to_string(CommandParseError err) RETURNS_NONNULL;
diff --git a/src/ctags.h b/src/ctags.h
index 3b49fe29..1317b0cc 100644
--- a/src/ctags.h
+++ b/src/ctags.h
@@ -15,7 +15,7 @@ typedef struct {
     bool local; // Indicates if tag is local to file (e.g. "static" in C)
 } Tag;
 
-NONNULL_ARGS WARN_UNUSED_RESULT
+NONNULL_ARGS WARN_UNUSED_RESULT READWRITE(3) WRITEONLY(6)
 bool next_tag (
     const char *buf,
     size_t buf_len,
diff --git a/src/insert.h b/src/insert.h
index c83f5a36..3cae0814 100644
--- a/src/insert.h
+++ b/src/insert.h
@@ -7,7 +7,7 @@
 #include "util/unicode.h"
 #include "view.h"
 
-void insert_text(View *view, const char *text, size_t size, bool move_after) NONNULL_ARG(1);
+void insert_text(View *view, const char *text, size_t size, bool move_after) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 void insert_ch(View *view, CodePoint ch) NONNULL_ARGS;
 void new_line(View *view, bool above) NONNULL_ARGS;
 
diff --git a/src/join.h b/src/join.h
index 002203bc..431d3479 100644
--- a/src/join.h
+++ b/src/join.h
@@ -5,6 +5,6 @@
 #include "view.h"
 #include "util/macros.h"
 
-void join_lines(View *view, const char *delim, size_t delim_len) NONNULL_ARG(1);
+void join_lines(View *view, const char *delim, size_t delim_len) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 
 #endif
diff --git a/src/regexp.h b/src/regexp.h
index 5f21f0ce..3e6ed575 100644
--- a/src/regexp.h
+++ b/src/regexp.h
@@ -39,7 +39,7 @@ void regexp_compile_or_fatal_error(regex_t *re, const char *pattern, int flags)
 bool regexp_init_word_boundary_tokens(RegexpWordBoundaryTokens *rwbt) NONNULL_ARGS;
 bool regexp_error_msg(ErrorBuffer *ebuf, const regex_t *re, const char *pattern, int err) NONNULL_ARG(2, 3);
 char *regexp_escape(const char *pattern, size_t len) NONNULL_ARGS WARN_UNUSED_RESULT;
-size_t regexp_escapeb(char *buf, size_t buflen, const char *pat, size_t plen) NONNULL_ARG(1);
+size_t regexp_escapeb(char *buf, size_t buflen, const char *pat, size_t plen) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(3, 4);
 
 const InternedRegexp *regexp_intern(ErrorBuffer *ebuf, const char *pattern) NONNULL_ARG(2) WARN_UNUSED_RESULT;
 bool regexp_is_interned(const char *pattern) NONNULL_ARGS;
diff --git a/src/util/macros.h b/src/util/macros.h
index 18c828f8..e6656e26 100644
--- a/src/util/macros.h
+++ b/src/util/macros.h
@@ -277,6 +277,20 @@
     #define NONSTRING
 #endif
 
+// https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-nonnull_005fif_005fnonzero-function-attribute
+#if HAS_ATTRIBUTE(nonnull_if_nonzero)
+    #define NONNULL_ARG_IF_NONZERO_LENGTH(...) __attribute__((__nonnull_if_nonzero__, __VA_ARGS__))
+#else
+    #define NONNULL_ARG_IF_NONZERO_LENGTH(...)
+#endif
+
+// https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-null_005fterminated_005fstring_005farg-function-attribute
+#if HAS_ATTRIBUTE(null_terminated_string_arg)
+    #define CSTR_ARG(idx) __attribute__((__null_terminated_string_arg__(idx)))
+#else
+    #define CSTR_ARG(idx)
+#endif
+
 #if HAS_ATTRIBUTE(counted_by)
     #define COUNTED_BY(member) __attribute__((counted_by(member)))
 #else
@@ -295,6 +309,17 @@
     #define DIAGNOSE_IF(x)
 #endif
 
+// https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-access-function-attribute
+#if HAS_ATTRIBUTE(access)
+    #define READONLY(...) __attribute__((__access__(read_only, __VA_ARGS__))) // in param
+    #define WRITEONLY(...) __attribute__((__access__(write_only, __VA_ARGS__))) // out param
+    #define READWRITE(...) __attribute__((__access__(read_write, __VA_ARGS__))) // in-out param
+#else
+    #define READONLY(...)
+    #define WRITEONLY(...)
+    #define READWRITE(...)
+#endif
+
 #define UNUSED_ARG(x) unused__ ## x UNUSED
 #define XMALLOC MALLOC RETURNS_NONNULL
 #define XSTRDUP XMALLOC NONNULL_ARGS
diff --git a/src/util/str-util.h b/src/util/str-util.h
index 07168049..c7b88f70 100644
--- a/src/util/str-util.h
+++ b/src/util/str-util.h
@@ -91,10 +91,10 @@ static inline void strn_replace_byte(char *str, size_t n, char byte, char rep)
 
 // Extract a substring between `buf + pos` and either the next `delim`
 // byte (if found) or `buf + size` (the remainder of the string). The
-// substring is returned as a StringView and the `posp` in-out-param
+// substring is returned as a StringView and the `posp` in-out param
 // is set to the offset one byte after the found delimiter (or to the
 // end of the size-bounded string, if no delimiter was found).
-NONNULL_ARGS
+NONNULL_ARGS READONLY(1, 3) READWRITE(2)
 static inline StringView get_delim(const char *buf, size_t *posp, size_t size, int delim)
 {
     size_t pos = *posp;
diff --git a/src/util/string-view.h b/src/util/string-view.h
index 370300bb..c890b470 100644
--- a/src/util/string-view.h
+++ b/src/util/string-view.h
@@ -80,13 +80,13 @@ static inline bool strview_equal_cstring_icase(const StringView *sv, const char
     return strview_equal_strn_icase(sv, str, strlen(str));
 }
 
-NONNULL_ARG(1)
+NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3)
 static inline bool strview_has_strn_prefix(const StringView *sv, const char *p, size_t n)
 {
     return sv->length >= n && mem_equal(sv->data, p, n);
 }
 
-NONNULL_ARG(1)
+NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3)
 static inline bool strview_has_strn_suffix(const StringView *sv, const char *suf, size_t suflen)
 {
     // See also: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3261.pdf
diff --git a/src/util/string.h b/src/util/string.h
index 85d604e6..a7561891 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -23,7 +23,7 @@ typedef struct {
 
 #define string_append_literal(s, x) string_append_buf(s, x, STRLEN(x))
 
-void string_append_buf(String *s, const char *ptr, size_t len) NONNULL_ARG(1);
+void string_append_buf(String *s, const char *ptr, size_t len) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(2, 3);
 
 static inline String string_new(size_t size)
 {
@@ -73,7 +73,7 @@ char *string_reserve_space(String *s, size_t more) NONNULL_ARGS_AND_RETURN;
 void string_append_byte(String *s, unsigned char byte) NONNULL_ARGS;
 size_t string_append_codepoint(String *s, CodePoint u) NONNULL_ARGS;
 size_t string_insert_codepoint(String *s, size_t pos, CodePoint u) NONNULL_ARGS;
-void string_insert_buf(String *s, size_t pos, const char *buf, size_t len) NONNULL_ARG(1);
+void string_insert_buf(String *s, size_t pos, const char *buf, size_t len) NONNULL_ARG(1) NONNULL_ARG_IF_NONZERO_LENGTH(3, 4);
 void string_append_memset(String *s, unsigned char byte, size_t len) NONNULL_ARGS;
 void string_sprintf(String *s, const char *fmt, ...) PRINTF(2) NONNULL_ARGS;
 char *string_steal_cstring(String *s) NONNULL_ARGS_AND_RETURN;