diff --git a/src/builtin.cpp b/src/builtin.cpp
index 7dd35f1c7..f735c2996 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -93,10 +93,10 @@ int builtin_count_args(const wchar_t *const *argv) {
 
 /// This function works like wperror, but it prints its result into the streams.err string instead
 /// to stderr. Used by the builtin commands.
-void builtin_wperror(const wchar_t *s, io_streams_t &streams) {
+void builtin_wperror(const wchar_t *program_name, io_streams_t &streams) {
     char *err = std::strerror(errno);
-    if (s != nullptr) {
-        streams.err.append(s);
+    if (program_name != nullptr) {
+        streams.err.append(program_name);
         streams.err.append(L": ");
     }
     if (err != nullptr) {
@@ -319,21 +319,21 @@ static maybe_t<int> builtin_breakpoint(parser_t &parser, io_streams_t &streams,
     return parser.get_last_status();
 }
 
-maybe_t<int> builtin_true(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
+static maybe_t<int> builtin_true(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
     UNUSED(parser);
     UNUSED(streams);
     UNUSED(argv);
     return STATUS_CMD_OK;
 }
 
-maybe_t<int> builtin_false(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
+static maybe_t<int> builtin_false(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
     UNUSED(parser);
     UNUSED(streams);
     UNUSED(argv);
     return STATUS_CMD_ERROR;
 }
 
-maybe_t<int> builtin_gettext(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
+static maybe_t<int> builtin_gettext(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {
     UNUSED(parser);
     UNUSED(streams);
     for (int i = 1; i < builtin_count_args(argv); i++) {
diff --git a/src/builtin.h b/src/builtin.h
index c13568ceb..1d6e35704 100644
--- a/src/builtin.h
+++ b/src/builtin.h
@@ -101,7 +101,7 @@ void builtin_missing_argument(parser_t &parser, io_streams_t &streams, const wch
 
 void builtin_print_error_trailer(parser_t &parser, output_stream_t &b, const wchar_t *cmd);
 
-void builtin_wperror(const wchar_t *s, io_streams_t &streams);
+void builtin_wperror(const wchar_t *program_name, io_streams_t &streams);
 
 struct help_only_cmd_opts_t {
     bool print_help = false;
diff --git a/src/builtin_set.cpp b/src/builtin_set.cpp
index c56aa364c..01ea013fd 100644
--- a/src/builtin_set.cpp
+++ b/src/builtin_set.cpp
@@ -17,6 +17,7 @@
 #include <vector>
 
 #include "builtin.h"
+#include "builtin_set.h"
 #include "common.h"
 #include "env.h"
 #include "expand.h"
@@ -313,7 +314,7 @@ struct split_var_t {
 /// Returns:
 ///   a split var on success, none() on error, in which case an error will have been printed.
 ///   If no index is found, this leaves indexes empty.
-maybe_t<split_var_t> split_var_and_indexes(const wchar_t *arg, env_mode_flags_t mode,
+static maybe_t<split_var_t> split_var_and_indexes(const wchar_t *arg, env_mode_flags_t mode,
                                            const environment_t &vars, io_streams_t &streams) {
     split_var_t res{};
     const wchar_t *open_bracket = std::wcschr(arg, L'[');
diff --git a/src/builtin_test.cpp b/src/builtin_test.cpp
index 60271db18..be20ffddf 100644
--- a/src/builtin_test.cpp
+++ b/src/builtin_test.cpp
@@ -124,7 +124,7 @@ struct token_info_t {
     unsigned int flags;
 };
 
-const token_info_t *token_for_string(const wcstring &str) {
+static const token_info_t *token_for_string(const wcstring &str) {
     static const std::map<wcstring, const token_info_t> token_infos = {
         {L"", {test_unknown, 0}},
         {L"!", {test_bang, 0}},
diff --git a/src/function.cpp b/src/function.cpp
index df12ec156..455f22557 100644
--- a/src/function.cpp
+++ b/src/function.cpp
@@ -77,7 +77,7 @@ bool function_set_t::allow_autoload(const wcstring &name) const {
 }  // namespace
 
 /// \return a copy of some function props, in a new shared_ptr.
-std::shared_ptr<function_properties_t> copy_props(const function_properties_ref_t &props) {
+static std::shared_ptr<function_properties_t> copy_props(const function_properties_ref_t &props) {
     assert(props && "Null props");
     return std::make_shared<function_properties_t>(*props);
 }
diff --git a/src/parse_constants.h b/src/parse_constants.h
index a495f6e35..904e75ad5 100644
--- a/src/parse_constants.h
+++ b/src/parse_constants.h
@@ -109,7 +109,7 @@ const enum_map<parse_keyword_t> keyword_enum_map[] = {{parse_keyword_t::kw_excla
 #define keyword_enum_map_len (sizeof keyword_enum_map / sizeof *keyword_enum_map)
 
 // Statement decorations like 'command' or 'exec'.
-enum class statement_decoration_t {
+enum class statement_decoration_t : uint8_t {
     none,
     command,
     builtin,
@@ -117,7 +117,7 @@ enum class statement_decoration_t {
 };
 
 // Parse error code list.
-enum parse_error_code_t {
+enum parse_error_code_t : uint8_t {
     parse_error_none,
 
     // Matching values from enum parser_error.
@@ -159,10 +159,10 @@ enum {
     /// Indicate that extra semis should be generated.
     parse_flag_show_extra_semis = 1 << 5,
 };
-typedef unsigned int parse_tree_flags_t;
+using parse_tree_flags_t = uint8_t;
 
 enum { PARSER_TEST_ERROR = 1, PARSER_TEST_INCOMPLETE = 2 };
-typedef unsigned int parser_test_error_bits_t;
+using parser_test_error_bits_t = uint8_t;
 
 struct parse_error_t {
     /// Text of the error.
@@ -193,7 +193,7 @@ wcstring token_type_user_presentable_description(parse_token_type_t type,
 void parse_error_offset_source_start(parse_error_list_t *errors, size_t amt);
 
 // The location of a pipeline.
-enum class pipeline_position_t {
+enum class pipeline_position_t : uint8_t {
     none,       // not part of a pipeline
     first,      // first command in a pipeline
     subsequent  // second or further command in a pipeline
diff --git a/src/path.cpp b/src/path.cpp
index 963a308ad..5f3cd991a 100644
--- a/src/path.cpp
+++ b/src/path.cpp
@@ -98,7 +98,7 @@ bool path_get_path(const wcstring &cmd, wcstring *out_path, const environment_t
     return path_get_path_core(cmd, out_path, vars.get(L"PATH"));
 }
 
-bool path_is_executable(const std::string &path) {
+static bool path_is_executable(const std::string &path) {
     if (access(path.c_str(), X_OK)) return false;
     struct stat buff;
     if (stat(path.c_str(), &buff) == -1) {
@@ -221,11 +221,11 @@ maybe_t<wcstring> path_get_cdpath(const wcstring &dir, const wcstring &wd,
     assert(!wd.empty() && wd.back() == L'/');
     auto paths = path_apply_cdpath(dir, wd, env_vars);
 
-    for (const wcstring &dir : paths) {
+    for (const wcstring &a_dir : paths) {
         struct stat buf;
-        if (wstat(dir, &buf) == 0) {
+        if (wstat(a_dir, &buf) == 0) {
             if (S_ISDIR(buf.st_mode)) {
-                return dir;
+                return a_dir;
             }
             err = ENOTDIR;
         }
diff --git a/src/proc.h b/src/proc.h
index 37ac8b950..cb0fe0894 100644
--- a/src/proc.h
+++ b/src/proc.h
@@ -24,7 +24,7 @@
 #include "wait_handle.h"
 
 /// Types of processes.
-enum class process_type_t {
+enum class process_type_t : uint8_t {
     /// A regular external command.
     external,
     /// A builtin command.
@@ -37,7 +37,7 @@ enum class process_type_t {
     exec,
 };
 
-enum class job_control_t {
+enum class job_control_t : uint8_t {
     all,
     interactive,
     none,
diff --git a/src/reader.cpp b/src/reader.cpp
index bc0176bae..edb3c7bdf 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -930,7 +930,7 @@ void term_copy_modes() {
 }
 
 /// Grab control of terminal.
-void term_steal() {
+static void term_steal() {
     term_copy_modes();
     while (true) {
         if (tcsetattr(STDIN_FILENO, TCSANOW, &shell_modes) == -1) {
@@ -4184,7 +4184,7 @@ void reader_queue_ch(const char_event_t &ch) {
 }
 
 /// Sets the command line contents, clearing the pager.
-void reader_set_buffer(const wcstring &b, size_t pos) {
+static void reader_set_buffer(const wcstring &b, size_t pos) {
     reader_data_t *data = current_data_or_null();
     if (!data) return;