diff --git a/build_tools/iwyu.osx.imp b/build_tools/iwyu.osx.imp
index e00305fed..f55ba0be4 100644
--- a/build_tools/iwyu.osx.imp
+++ b/build_tools/iwyu.osx.imp
@@ -1,6 +1,6 @@
 # Map file for the include-what-you-use tool on OS X. For some reason
 # the version installed by HomeBrew doesn't have useful mappings for the
-# system provided private headers.
+# system provided headers. This also has mappings for FreeBSD.
 [
     { include: ["<sys/_pthread/_pthread_once_t.h>", "private", "<pthread.h>", "public"] },
     { include: ["<sys/_pthread/_pthread_mutex_t.h>", "private", "<pthread.h>", "public"] },
@@ -9,6 +9,7 @@
     { include: ["<sys/_pthread/_pthread_cond_t.h>", "private", "<pthread.h>", "public"] },
     { include: ["<sys/_pthread/_pthread_t.h>", "private", "<pthread.h>", "public"] },
     { include: ["<sys/_pthread/_pthread_key_t.h>", "private", "<pthread.h>", "public"] },
+    { include: ["<sys/_pthreadtypes.h>", "private", "<pthread.h>", "public"] },
     { include: ["<sys/_types/_posix_vdisable.h>", "private", "<pthread.h>", "public"] },
     { include: ["<sys/_types/_time_t.h>", "private", "<time.h>", "public"] },
     { include: ["<sys/_types/_suseconds_t.h>", "private", "<time.h>", "public"] },
@@ -20,6 +21,7 @@
     { include: ["<sys/_types/_seek_set.h>", "private", "<fcntl.h>", "public"] },
     { include: ["<sys/_types/_mbstate_t.h>", "private", "<wchar.h>", "public"] },
     { include: ["<iosfwd>", "private", "<string>", "public"] },
+    { include: ["<sys/_stdint.h>", "private", "<stdint.h>", "public"] },
     { include: ["<sys/_types/_s_ifmt.h>", "private", "<sys/types.h>", "public"] },
     { include: ["<sys/_types/_size_t.h>", "private", "<sys/types.h>", "public"] },
     { include: ["<sys/_types/_size_t.h>", "private", "<stdlib.h>", "public"] },
@@ -51,32 +53,35 @@
     { include: ["<sys/signal.h>", "private", "<signal.h>", "public"] },
     { include: ["<strings.h>", "private", "<string.h>", "public"] },
     { include: ["<sys/termios.h>", "private", "<termios.h>", "public"] },
+    { include: ["<sys/_termios.h>", "private", "<termios.h>", "public"] },
     { include: ["<sys/ttycom.h>", "private", "<termios.h>", "public"] },
     { include: ["<sys/syslimits.h>", "private", "<limits.h>", "public"] },
     { include: ["<i386/limits.h>", "private", "<limits.h>", "public"] },
+    { include: ["<sys/limits.h>", "private", "<limits.h>", "public"] },
     { include: ["<sys/_types/_wint_t.h>", "private", "<stddef.h>", "public"] },
     { include: ["<sys/_select.h>", "private", "<select.h>", "public"] },
     { include: ["<sys/cdefs.h>", "private", "<unistd.h>", "public"] },
     { include: ["<istream>", "private", "<iostream>", "public"] },
     { include: ["<sys/_endian.h>", "private", "<netinet/in.h>", "public"] },
     { include: ["<sys/_types/_timespec.h>", "private", "<time.h>", "public"] },
+    { include: ["<sys/_timespec.h>", "private", "<time.h>", "public"] },
     { include: ["<sys/spawn.h>", "private", "<spawn.h>", "public"] },
     { include: ["<sys/dirent.h>", "private", "<dirent.h>", "public"] },
 #   { include: ["<>", "private", "<>", "public"] },
 
+    { symbol: ["sig_atomic_t", "private", "<csignal>", "public"] },
+    { symbol: ["va_end", "private", "<stdarg.h>", "public"] },
+    { symbol: ["va_list", "private", "<stdarg.h>", "public"] },
+    { symbol: ["va_start", "private", "<stdarg.h>", "public"] },
     { symbol: ["NULL", "private", "<stddef.h>", "public"] },
     { symbol: ["NULL", "private", "<stdlib.h>", "public"] },
     { symbol: ["NULL", "private", "<stdio.h>", "public"] },
     { symbol: ["NULL", "private", "<unistd.h>", "public"] },
     { symbol: ["off_t", "private", "<unistd.h>", "public"] },
-    { symbol: ["size_t", "private", "<unistd.h>", "public"] },
-    { symbol: ["size_t", "private", "<stddef.h>", "public"] },
-    { symbol: ["size_t", "private", "<stdlib.h>", "public"] },
     { symbol: ["off_t", "private", "<sys/types.h>", "public"] },
-    { symbol: ["size_t", "private", "<sys/types.h>", "public"] },
-    { symbol: ["ssize_t", "private", "<sys/types.h>", "public"] },
+    { symbol: ["size_t", "private", "<stddef.h>", "public"] },
+    { symbol: ["ssize_t", "private", "<stddef.h>", "public"] },
     { symbol: ["intptr_t", "private", "<unistd.h>", "public"] },
-    { symbol: ["ssize_t", "private", "<unistd.h>", "public"] },
     { symbol: ["gid_t", "private", "<unistd.h>", "public"] },
     { symbol: ["uid_t", "private", "<unistd.h>", "public"] },
     { symbol: ["pid_t", "private", "<unistd.h>", "public"] },
@@ -84,11 +89,9 @@
     { symbol: ["uid_t", "private", "<sys/types.h>", "public"] },
     { symbol: ["gid_t", "private", "<sys/types.h>", "public"] },
     { symbol: ["timeval", "private", "<sys/time.h>", "public"] },
-    { symbol: ["__uint32_t", "private", "<sys/types.h>", "public"] },
-    { symbol: ["uint32_t", "private", "<sys/types.h>", "public"] },
+    { symbol: ["__uint32_t", "private", "<stdint.h>", "public"] },
     { symbol: ["uint32_t", "private", "<stdint.h>", "public"] },
     { symbol: ["intptr_t", "private", "<stdint.h>", "public"] },
-    { symbol: ["size_t", "private", "<stdint.h>", "public"] },
     { symbol: ["tparm", "private", "<ncurses.h>", "public"] },
     { symbol: ["ERR", "private", "<ncurses.h>", "public"] },
     { symbol: ["select", "private", "<sys/select.h>", "public"] },
diff --git a/build_tools/lint.fish b/build_tools/lint.fish
index f54b1dd7c..266c15027 100755
--- a/build_tools/lint.fish
+++ b/build_tools/lint.fish
@@ -76,9 +76,6 @@ if set -q c_files[1]
         echo ========================================
         echo Running IWYU
         echo ========================================
-        # The stderr to stdout redirection is because cppcheck, incorrectly IMHO, writes its
-        # diagnostic messages to stderr. Anyone running this who wants to capture its output will
-        # expect those messages to be written to stdout.
         for c_file in $c_files
             switch $kernel_name
                 case Darwin FreeBSD
diff --git a/src/autoload.cpp b/src/autoload.cpp
index 960b586e7..7ecd3cbe9 100644
--- a/src/autoload.cpp
+++ b/src/autoload.cpp
@@ -4,9 +4,11 @@
 #include <assert.h>
 #include <errno.h>
 #include <pthread.h>
+#include <stddef.h>
 #include <sys/stat.h>
 #include <time.h>
 #include <unistd.h>
+
 #include <memory>
 #include <set>
 #include <string>
diff --git a/src/builtin.cpp b/src/builtin.cpp
index 47d5d2edb..e7470806c 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -23,10 +23,10 @@
 #include <limits.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
-#include <sys/types.h>
 #include <unistd.h>
 #include <wchar.h>
 #include <algorithm>
diff --git a/src/builtin_commandline.cpp b/src/builtin_commandline.cpp
index 2ba5b2356..1a81226bb 100644
--- a/src/builtin_commandline.cpp
+++ b/src/builtin_commandline.cpp
@@ -3,6 +3,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <stddef.h>
 #include <stdlib.h>
 #include <wchar.h>
 
diff --git a/src/builtin_complete.cpp b/src/builtin_complete.cpp
index 30fe087be..b80d7e89b 100644
--- a/src/builtin_complete.cpp
+++ b/src/builtin_complete.cpp
@@ -1,8 +1,9 @@
 // Functions used for implementing the complete builtin.
 #include "config.h"  // IWYU pragma: keep
 
-#include <stdlib.h>
+#include <stddef.h>
 #include <wchar.h>
+
 #include <memory>
 #include <string>
 #include <vector>
diff --git a/src/builtin_printf.cpp b/src/builtin_printf.cpp
index b26ecf49f..4f41505e2 100644
--- a/src/builtin_printf.cpp
+++ b/src/builtin_printf.cpp
@@ -54,6 +54,8 @@
 #include <limits.h>
 #include <locale.h>
 #include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
diff --git a/src/builtin_set.cpp b/src/builtin_set.cpp
index b89c12e23..9aa5519e2 100644
--- a/src/builtin_set.cpp
+++ b/src/builtin_set.cpp
@@ -2,12 +2,14 @@
 #include "config.h"  // IWYU pragma: keep
 
 #include <errno.h>
+#include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <wchar.h>
 #include <wctype.h>
+
 #include <algorithm>
 #include <iterator>
 #include <memory>
diff --git a/src/builtin_set_color.cpp b/src/builtin_set_color.cpp
index 40390ffff..fcbf5b02d 100644
--- a/src/builtin_set_color.cpp
+++ b/src/builtin_set_color.cpp
@@ -13,7 +13,9 @@
 #elif HAVE_NCURSES_TERM_H
 #include <ncurses/term.h>
 #endif
+
 #include <assert.h>
+#include <stddef.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <memory>
diff --git a/src/builtin_string.cpp b/src/builtin_string.cpp
index 3547e88c8..4293b0d06 100644
--- a/src/builtin_string.cpp
+++ b/src/builtin_string.cpp
@@ -9,10 +9,12 @@
 #include <errno.h>
 #include <limits.h>
 #include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
-#include <sys/types.h>
 #include <wchar.h>
 #include <wctype.h>
+
 #include <algorithm>
 #include <iterator>
 #include <memory>
diff --git a/src/color.cpp b/src/color.cpp
index 19cf2228b..235e70841 100644
--- a/src/color.cpp
+++ b/src/color.cpp
@@ -2,6 +2,7 @@
 #include "config.h"  // IWYU pragma: keep
 
 #include <assert.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <wchar.h>  // IWYU pragma: keep
diff --git a/src/common.cpp b/src/common.cpp
index 174cbd575..db906422e 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -15,7 +15,6 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/time.h>
-#include <sys/types.h>
 #include <termios.h>
 #include <unistd.h>
 #include <wchar.h>
diff --git a/src/common.h b/src/common.h
index 91d4396b4..0d1ee5777 100644
--- a/src/common.h
+++ b/src/common.h
@@ -6,10 +6,10 @@
 #include <errno.h>
 #include <pthread.h>
 #include <stdarg.h>  // IWYU pragma: keep
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/types.h>
 #include <termios.h>
 #include <wchar.h>
 #include <memory>
diff --git a/src/env_universal_common.cpp b/src/env_universal_common.cpp
index 0047283cf..47b54cd4c 100644
--- a/src/env_universal_common.cpp
+++ b/src/env_universal_common.cpp
@@ -15,6 +15,8 @@
 #if !defined(__APPLE__) && !defined(__CYGWIN__)
 #include <pwd.h>
 #endif
+#include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #ifdef __CYGWIN__
@@ -26,9 +28,9 @@
 #include <sys/stat.h>
 #include <sys/time.h>  // IWYU pragma: keep
 #include <sys/types.h>  // IWYU pragma: keep
-
 #include <unistd.h>
 #include <wchar.h>
+
 #include <atomic>
 #include <map>
 #include <string>
diff --git a/src/event.cpp b/src/event.cpp
index 2b0a68c8c..3fb88b43c 100644
--- a/src/event.cpp
+++ b/src/event.cpp
@@ -2,6 +2,7 @@
 #include "config.h"  // IWYU pragma: keep
 
 #include <signal.h>
+#include <stddef.h>
 #include <unistd.h>
 
 #include <algorithm>
diff --git a/src/expand.cpp b/src/expand.cpp
index a6bec6e0f..90f3305e6 100644
--- a/src/expand.cpp
+++ b/src/expand.cpp
@@ -12,13 +12,13 @@
 #include <unistd.h>
 #include <wchar.h>
 #include <wctype.h>
+
 #ifdef HAVE_SYS_SYSCTL_H
 #include <sys/sysctl.h>  // IWYU pragma: keep
 #endif
 #ifdef SunOS
 #include <procfs.h>
 #endif
-#include <stdio.h>
 #if __APPLE__
 #include <sys/proc.h>
 #else
diff --git a/src/fallback.h b/src/fallback.h
index cb5775c35..e8ddfec03 100644
--- a/src/fallback.h
+++ b/src/fallback.h
@@ -7,6 +7,7 @@
 // compiling several modules that include this header because they use symbols which are defined as
 // macros in <term.h>.
 // IWYU pragma: no_include <term.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <unistd.h>
 // The following include must be kept despite what IWYU says. That's because of the interaction
diff --git a/src/fish.cpp b/src/fish.cpp
index 39ebab886..5b74264a4 100644
--- a/src/fish.cpp
+++ b/src/fish.cpp
@@ -22,6 +22,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 #include <getopt.h>
 #include <limits.h>
 #include <locale.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/src/fish_key_reader.cpp b/src/fish_key_reader.cpp
index b850cbd28..69819ffc1 100644
--- a/src/fish_key_reader.cpp
+++ b/src/fish_key_reader.cpp
@@ -11,12 +11,14 @@
 #include <errno.h>
 #include <getopt.h>
 #include <signal.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <termios.h>
 #include <unistd.h>
 #include <wchar.h>
+
 #include <memory>
 #include <string>
 #include <vector>
diff --git a/src/highlight.h b/src/highlight.h
index bffe6ba13..a4fd9b6bd 100644
--- a/src/highlight.h
+++ b/src/highlight.h
@@ -3,6 +3,7 @@
 #define FISH_HIGHLIGHT_H
 
 #include <assert.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <vector>
 
diff --git a/src/history.cpp b/src/history.cpp
index 73e511721..31b04263d 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -6,6 +6,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/src/history.h b/src/history.h
index c64625eed..6a29d20ce 100644
--- a/src/history.h
+++ b/src/history.h
@@ -4,6 +4,7 @@
 
 // IWYU pragma: no_include <cstddef>
 #include <pthread.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <time.h>
diff --git a/src/parse_tree.h b/src/parse_tree.h
index c5652cff0..4f78fd4b0 100644
--- a/src/parse_tree.h
+++ b/src/parse_tree.h
@@ -4,6 +4,7 @@
 
 #include <assert.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <sys/types.h>
 #include <memory>
 #include <vector>
diff --git a/src/parse_util.cpp b/src/parse_util.cpp
index 98a0ec65b..eea3680a8 100644
--- a/src/parse_util.cpp
+++ b/src/parse_util.cpp
@@ -6,7 +6,6 @@
 
 #include <assert.h>
 #include <stdarg.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <wchar.h>
 
diff --git a/src/postfork.h b/src/postfork.h
index df0a74cba..0a82a4553 100644
--- a/src/postfork.h
+++ b/src/postfork.h
@@ -5,6 +5,7 @@
 
 #include "config.h"
 
+#include <stddef.h>
 #include <unistd.h>
 #if HAVE_SPAWN_H
 #include <spawn.h>
diff --git a/src/screen.h b/src/screen.h
index 3d515a2fb..6ae6f0cb7 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -8,13 +8,14 @@
 // of text around to handle text insertion.
 #ifndef FISH_SCREEN_H
 #define FISH_SCREEN_H
+#include "config.h"  // IWYU pragma: keep
 
 #include <assert.h>
 #include <stddef.h>
 #include <sys/stat.h>
-#include <sys/types.h>
 
 #include <algorithm>
+#include <cstddef>
 #include <map>
 #include <memory>
 #include <set>
diff --git a/src/wildcard.cpp b/src/wildcard.cpp
index 15fbe59de..8cc6ca3de 100644
--- a/src/wildcard.cpp
+++ b/src/wildcard.cpp
@@ -5,10 +5,12 @@
 #include <assert.h>
 #include <dirent.h>
 #include <errno.h>
+#include <stddef.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <wchar.h>
+
 #include <memory>
 #include <set>
 #include <string>