diff --git a/src/common.cpp b/src/common.cpp
index 98e3852e5..458838181 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1966,7 +1966,7 @@ bool is_console_session() {
         ASSERT_IS_MAIN_THREAD();
 
         const char *tty_name = ttyname(0);
-        auto len = strlen("/dev/tty");
+        constexpr auto len = const_strlen("/dev/tty");
         const char *TERM = getenv("TERM");
         return
             // Test that the tty matches /dev/(console|dcons|tty[uv\d])
diff --git a/src/env_dispatch.cpp b/src/env_dispatch.cpp
index 35052206f..376e185be 100644
--- a/src/env_dispatch.cpp
+++ b/src/env_dispatch.cpp
@@ -461,9 +461,9 @@ static bool does_term_support_setting_title(const environment_t &vars) {
     const wcstring term_str = term_var->as_string();
     const wchar_t *term = term_str.c_str();
     bool recognized = contains(title_terms, term_var->as_string());
-    if (!recognized) recognized = !std::wcsncmp(term, L"xterm-", std::wcslen(L"xterm-"));
-    if (!recognized) recognized = !std::wcsncmp(term, L"screen-", std::wcslen(L"screen-"));
-    if (!recognized) recognized = !std::wcsncmp(term, L"tmux-", std::wcslen(L"tmux-"));
+    if (!recognized) recognized = !std::wcsncmp(term, L"xterm-", const_strlen(L"xterm-"));
+    if (!recognized) recognized = !std::wcsncmp(term, L"screen-", const_strlen(L"screen-"));
+    if (!recognized) recognized = !std::wcsncmp(term, L"tmux-", const_strlen(L"tmux-"));
     if (!recognized) {
         if (std::wcscmp(term, L"linux") == 0) return false;
         if (std::wcscmp(term, L"dumb") == 0) return false;
diff --git a/src/fish_indent.cpp b/src/fish_indent.cpp
index e1b75058c..c4a43ab41 100644
--- a/src/fish_indent.cpp
+++ b/src/fish_indent.cpp
@@ -602,7 +602,7 @@ struct pretty_printer_t {
             bool added_newline = emit_gap_text_before(node.range, flags);
             wcstring text = source.substr(node.range.start, node.range.length);
             if (added_newline && !text.empty() && text.front() == L'\n') {
-                text = text.substr(strlen("\n"));
+                text = text.substr(const_strlen("\n"));
             }
             emit_gap_text(text, flags);
         }
diff --git a/src/fish_key_reader.cpp b/src/fish_key_reader.cpp
index 63cb4fc85..39c7bfe5e 100644
--- a/src/fish_key_reader.cpp
+++ b/src/fish_key_reader.cpp
@@ -63,7 +63,8 @@ static bool should_exit(wchar_t wc) {
         std::fwprintf(stderr, L"Press [ctrl-%c] again to exit\n", shell_modes.c_cc[VEOF] + 0x40);
         return false;
     }
-    return std::memcmp(recent_chars, "exit", 4) == 0 || std::memcmp(recent_chars, "quit", 4) == 0;
+    return std::memcmp(recent_chars, "exit", const_strlen("exit")) == 0 ||
+           std::memcmp(recent_chars, "quit", const_strlen("quit")) == 0;
 }
 
 /// Return the name if the recent sequence of characters matches a known terminfo sequence.
diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index 01ecc876f..808763283 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -1497,12 +1497,12 @@ static void test_parse_util_cmdsubst_extent() {
     }
 
     parse_util_cmdsubst_extent(a, 8, &begin, &end);
-    if (begin != a + std::wcslen(L"echo (")) {
+    if (begin != a + const_strlen(L"echo (")) {
         err(L"parse_util_cmdsubst_extent failed on line %ld", (long)__LINE__);
     }
 
     parse_util_cmdsubst_extent(a, 17, &begin, &end);
-    if (begin != a + std::wcslen(L"echo (echo (")) {
+    if (begin != a + const_strlen(L"echo (echo (")) {
         err(L"parse_util_cmdsubst_extent failed on line %ld", (long)__LINE__);
     }
 }
@@ -1811,7 +1811,7 @@ static void test_escape_sequences() {
         err(L"test_escape_sequences failed on line %d\n", __LINE__);
     if (lc.escape_code_length(L"\x1B[2J") != 4)
         err(L"test_escape_sequences failed on line %d\n", __LINE__);
-    if (lc.escape_code_length(L"\x1B[38;5;123mABC") != std::strlen("\x1B[38;5;123m"))
+    if (lc.escape_code_length(L"\x1B[38;5;123mABC") != const_strlen("\x1B[38;5;123m"))
         err(L"test_escape_sequences failed on line %d\n", __LINE__);
     if (lc.escape_code_length(L"\x1B@") != 2)
         err(L"test_escape_sequences failed on line %d\n", __LINE__);
@@ -2285,41 +2285,41 @@ static void test_abbreviations() {
     result = expand_abbreviation_in_command(L"gc somebranch", 0, vars);
     if (!result) err(L"Command not expanded on line %ld", (long)__LINE__);
 
-    result = expand_abbreviation_in_command(L"gc somebranch", std::wcslen(L"gc"), vars);
+    result = expand_abbreviation_in_command(L"gc somebranch", const_strlen(L"gc"), vars);
     if (!result) err(L"gc not expanded");
     if (result != L"git checkout somebranch")
         err(L"gc incorrectly expanded on line %ld to '%ls'", (long)__LINE__, result->c_str());
 
     // Space separation.
-    result = expand_abbreviation_in_command(L"gx somebranch", std::wcslen(L"gc"), vars);
+    result = expand_abbreviation_in_command(L"gx somebranch", const_strlen(L"gc"), vars);
     if (!result) err(L"gx not expanded");
     if (result != L"git checkout somebranch")
         err(L"gc incorrectly expanded on line %ld to '%ls'", (long)__LINE__, result->c_str());
 
-    result = expand_abbreviation_in_command(L"echo hi ; gc somebranch", std::wcslen(L"echo hi ; g"),
-                                            vars);
+    result = expand_abbreviation_in_command(L"echo hi ; gc somebranch",
+                                            const_strlen(L"echo hi ; g"), vars);
     if (!result) err(L"gc not expanded on line %ld", (long)__LINE__);
     if (result != L"echo hi ; git checkout somebranch")
         err(L"gc incorrectly expanded on line %ld", (long)__LINE__);
 
     result = expand_abbreviation_in_command(L"echo (echo (echo (echo (gc ",
-                                            std::wcslen(L"echo (echo (echo (echo (gc"), vars);
+                                            const_strlen(L"echo (echo (echo (echo (gc"), vars);
     if (!result) err(L"gc not expanded on line %ld", (long)__LINE__);
     if (result != L"echo (echo (echo (echo (git checkout ")
         err(L"gc incorrectly expanded on line %ld to '%ls'", (long)__LINE__, result->c_str());
 
     // If commands should be expanded.
-    result = expand_abbreviation_in_command(L"if gc", std::wcslen(L"if gc"), vars);
+    result = expand_abbreviation_in_command(L"if gc", const_strlen(L"if gc"), vars);
     if (!result) err(L"gc not expanded on line %ld", (long)__LINE__);
     if (result != L"if git checkout")
         err(L"gc incorrectly expanded on line %ld to '%ls'", (long)__LINE__, result->c_str());
 
     // Others should not be.
-    result = expand_abbreviation_in_command(L"of gc", std::wcslen(L"of gc"), vars);
+    result = expand_abbreviation_in_command(L"of gc", const_strlen(L"of gc"), vars);
     if (result) err(L"gc incorrectly expanded on line %ld", (long)__LINE__);
 
     // Others should not be.
-    result = expand_abbreviation_in_command(L"command gc", std::wcslen(L"command gc"), vars);
+    result = expand_abbreviation_in_command(L"command gc", const_strlen(L"command gc"), vars);
     if (result) err(L"gc incorrectly expanded on line %ld", (long)__LINE__);
 
     vars.pop();
@@ -3824,10 +3824,10 @@ static void test_universal_ok_to_save() {
     // Ensure we don't try to save after reading from a newer fish.
     say(L"Testing universal Ok to save");
     if (system("mkdir -p test/fish_uvars_test/")) err(L"mkdir failed");
-    const char *contents = "# VERSION: 99999.99\n";
+    constexpr const char *contents = "# VERSION: 99999.99\n";
     FILE *fp = fopen(wcs2string(UVARS_TEST_PATH).c_str(), "w");
     assert(fp && "Failed to open UVARS_TEST_PATH for writing");
-    fwrite(contents, std::strlen(contents), 1, fp);
+    fwrite(contents, const_strlen(contents), 1, fp);
     fclose(fp);
 
     file_id_t before_id = file_id_for_path(UVARS_TEST_PATH);
diff --git a/src/future_feature_flags.cpp b/src/future_feature_flags.cpp
index a2305bbc7..54673d3b1 100644
--- a/src/future_feature_flags.cpp
+++ b/src/future_feature_flags.cpp
@@ -40,7 +40,7 @@ void features_t::set_from_string(const wcstring &str) {
         // A "no-" prefix inverts the sense.
         if (string_prefixes_string(L"no-", name)) {
             value = false;
-            name += 3;  // std::wcslen(L"no-")
+            name += const_strlen("no-");
         }
         // Look for a feature with this name. If we don't find it, assume it's a group name and set
         // all features whose group contain it. Do nothing even if the string is unrecognized; this
diff --git a/src/history_file.cpp b/src/history_file.cpp
index 909e670f9..7fb0fdc86 100644
--- a/src/history_file.cpp
+++ b/src/history_file.cpp
@@ -370,18 +370,18 @@ static size_t offset_of_next_item_fish_2_0(const history_file_contents_t &conten
 
         // Hackish: fish 1.x rewriting a fish 2.0 history file can produce lines with lots of
         // leading "- cmd: - cmd: - cmd:". Trim all but one leading "- cmd:".
-        const char *double_cmd = "- cmd: - cmd: ";
-        const size_t double_cmd_len = std::strlen(double_cmd);
+        constexpr const char *double_cmd = "- cmd: - cmd: ";
+        constexpr const size_t double_cmd_len = const_strlen(double_cmd);
         while (static_cast<size_t>(a_newline - line_start) > double_cmd_len &&
                !std::memcmp(line_start, double_cmd, double_cmd_len)) {
             // Skip over just one of the - cmd. In the end there will be just one left.
-            line_start += std::strlen("- cmd: ");
+            line_start += const_strlen("- cmd: ");
         }
 
         // Hackish: fish 1.x rewriting a fish 2.0 history file can produce commands like "when:
         // 123456". Ignore those.
-        const char *cmd_when = "- cmd:    when:";
-        const size_t cmd_when_len = std::strlen(cmd_when);
+        constexpr const char *cmd_when = "- cmd:    when:";
+        constexpr const size_t cmd_when_len = const_strlen(cmd_when);
         if (static_cast<size_t>(a_newline - line_start) >= cmd_when_len &&
             !std::memcmp(line_start, cmd_when, cmd_when_len)) {
             continue;
diff --git a/src/postfork.cpp b/src/postfork.cpp
index fd1d774d5..0bdebf025 100644
--- a/src/postfork.cpp
+++ b/src/postfork.cpp
@@ -425,9 +425,9 @@ static char *get_interpreter(const char *command, char *buffer, size_t buff_size
         close(fd);
     }
 
-    if (std::strncmp(buffer, "#! /", 4) == 0) {
+    if (std::strncmp(buffer, "#! /", const_strlen("#! /")) == 0) {
         return buffer + 3;
-    } else if (std::strncmp(buffer, "#!/", 3) == 0) {
+    } else if (std::strncmp(buffer, "#!/", const_strlen("#!/")) == 0) {
         return buffer + 2;
     }
     return nullptr;
diff --git a/src/signal.cpp b/src/signal.cpp
index 0b01112b9..c763b861d 100644
--- a/src/signal.cpp
+++ b/src/signal.cpp
@@ -145,9 +145,9 @@ static const struct lookup_entry signal_table[] = {
 
 /// Test if \c name is a string describing the signal named \c canonical.
 static int match_signal_name(const wchar_t *canonical, const wchar_t *name) {
-    if (wcsncasecmp(name, L"sig", 3) == 0) name += 3;
+    if (wcsncasecmp(name, L"sig", const_strlen("sig")) == 0) name += 3;
 
-    return wcscasecmp(canonical + 3, name) == 0;
+    return wcscasecmp(canonical + const_strlen("sig"), name) == 0;
 }
 
 int wcs2sig(const wchar_t *str) {
@@ -187,10 +187,10 @@ static const pid_t s_main_pid = getpid();
 
 /// It's possible that we receive a signal after we have forked, but before we have reset the signal
 /// handlers (or even run the pthread_atfork calls). In that event we will do something dumb like
-/// swallow SIGINT. Ensure that doesn't happen. Check if we are the main fish process; if not reset
+/// swallow SIGINT. Ensure that doesn't happen. Check if we are the main fish process; if not, reset
 /// and re-raise the signal. \return whether we re-raised the signal.
 static bool reraise_if_forked_child(int sig) {
-    // Don't use is_forked_child, that relies on atfork handlers which maybe have not run yet.
+    // Don't use is_forked_child: it relies on atfork handlers which may have not yet run.
     if (getpid() == s_main_pid) {
         return false;
     }