diff --git a/ci/config.mk.clang-12.sed b/ci/config.mk.clang-12.sed
index e305c59..810b723 100644
--- a/ci/config.mk.clang-12.sed
+++ b/ci/config.mk.clang-12.sed
@@ -1,3 +1,3 @@
 # Clang 12 (or Apple clang 13) and later makes a warning '-Wcompound-token-split-by-macro' enable by default.
-/^PERL_CFLAGS[[:blank:]]*=/s/$/ -Wno-error=compound-token-split-by-macro/
-/^RUBY_CFLAGS[[:blank:]]*=/s/$/ -Wno-error=compound-token-split-by-macro/
+/^PERL_CFLAGS_EXTRA[[:blank:]]*=/s/$/ -Wno-error=compound-token-split-by-macro/
+/^RUBY_CFLAGS_EXTRA[[:blank:]]*=/s/$/ -Wno-error=compound-token-split-by-macro/
diff --git a/ci/config.mk.clang.sed b/ci/config.mk.clang.sed
index da6044d..9dc271c 100644
--- a/ci/config.mk.clang.sed
+++ b/ci/config.mk.clang.sed
@@ -1,2 +1,2 @@
 /^CFLAGS[[:blank:]]*=/s/$/ -Wno-error=missing-field-initializers/
-/^RUBY_CFLAGS[[:blank:]]*=/s/$/ -Wno-error=unknown-attributes -Wno-error=ignored-attributes/
+/^RUBY_CFLAGS_EXTRA[[:blank:]]*=/s/$/ -Wno-error=unknown-attributes -Wno-error=ignored-attributes/
diff --git a/ci/config.mk.sed b/ci/config.mk.sed
index cd2cd9c..51e7ec9 100644
--- a/ci/config.mk.sed
+++ b/ci/config.mk.sed
@@ -1,2 +1,3 @@
 /^CFLAGS[[:blank:]]*=/s/$/ -Wall -Wextra -Wshadow -Werror/
-/^PERL_CFLAGS[[:blank:]]*=/s/$/ -Wno-error=unused-function/
+/^PERL_CFLAGS_EXTRA[[:blank:]]*=/s/$/ -Wno-error=unused-function/
+/^RUBY_CFLAGS_EXTRA[[:blank:]]*=/s/$/ -Wno-error=unused-parameter/
diff --git a/src/Makefile b/src/Makefile
index d21facd..aafe139 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1491,13 +1491,14 @@
 
 ALL_CFLAGS = $(PRE_DEFS) $(CFLAGS) $(PROFILE_CFLAGS) $(SANITIZER_CFLAGS) $(LEAK_CFLAGS) $(ABORT_CFLAGS) $(POST_DEFS)
 
+ALL_IF_CFLAGS = $(LUA_CFLAGS) $(PERL_CFLAGS) $(PYTHON_CFLAGS) $(PYTHON3_CFLAGS) $(RUBY_CFLAGS) $(TCL_CFLAGS)
+ALL_IF_CFLAGS_EXTRA = $(LUA_CFLAGS_EXTRA) $(PERL_CFLAGS_EXTRA) $(PYTHON_CFLAGS_EXTRA) $(PYTHON3_CFLAGS_EXTRA) $(RUBY_CFLAGS_EXTRA) $(TCL_CFLAGS_EXTRA)
+
 # Exclude $CFLAGS for osdef.sh, for Mac 10.4 some flags don't work together
 # with "-E".
 OSDEF_CFLAGS = $(PRE_DEFS) $(POST_DEFS)
 
-LINT_CFLAGS = -DLINT -I. $(PRE_DEFS) $(POST_DEFS) \
-	      $(RUBY_CFLAGS) $(LUA_CFLAGS) $(PERL_CFLAGS) $(PYTHON_CFLAGS) \
-	      $(PYTHON3_CFLAGS) $(TCL_CFLAGS) $(VTERM_CFLAGS) \
+LINT_CFLAGS = -DLINT -I. $(PRE_DEFS) $(POST_DEFS) $(ALL_IF_CFLAGS) $(VTERM_CFLAGS) \
 	      -Dinline= -D__extension__= -Dalloca=alloca
 
 LINT_EXTRA = -D"__attribute__(x)="
@@ -3357,7 +3358,7 @@
 	$(CCC) -o $@ if_xcmdsrv.c
 
 objects/if_lua.o: if_lua.c
-	$(CCC_NF) $(LUA_CFLAGS) $(ALL_CFLAGS) -o $@ if_lua.c
+	$(CCC_NF) $(LUA_CFLAGS) $(ALL_CFLAGS) $(LUA_CFLAGS_EXTRA) -o $@ if_lua.c
 
 objects/if_mzsch.o: if_mzsch.c $(MZSCHEME_EXTRA)
 	$(CCC) -o $@ $(MZSCHEME_CFLAGS_EXTRA) if_mzsch.c
@@ -3366,22 +3367,22 @@
 	$(MZSCHEME_MZC) --c-mods mzscheme_base.c ++lib scheme/base
 
 objects/if_perl.o: auto/if_perl.c
-	$(CCC_NF) $(PERL_CFLAGS) $(ALL_CFLAGS) -o $@ auto/if_perl.c
+	$(CCC_NF) $(PERL_CFLAGS) $(ALL_CFLAGS) $(PERL_CFLAGS_EXTRA) -o $@ auto/if_perl.c
 
 objects/if_perlsfio.o: if_perlsfio.c
-	$(CCC_NF) $(PERL_CFLAGS) $(ALL_CFLAGS) -o $@ if_perlsfio.c
+	$(CCC_NF) $(PERL_CFLAGS) $(ALL_CFLAGS) $(PERL_CFLAGS_EXTRA) -o $@ if_perlsfio.c
 
 objects/if_python.o: if_python.c if_py_both.h
-	$(CCC_NF) $(PYTHON_CFLAGS) $(PYTHON_CFLAGS_EXTRA) $(ALL_CFLAGS) -o $@ if_python.c
+	$(CCC_NF) $(PYTHON_CFLAGS) $(ALL_CFLAGS) $(PYTHON_CFLAGS_EXTRA) -o $@ if_python.c
 
 objects/if_python3.o: if_python3.c if_py_both.h
-	$(CCC_NF) $(PYTHON3_CFLAGS) $(PYTHON3_CFLAGS_EXTRA) $(ALL_CFLAGS) -o $@ if_python3.c
+	$(CCC_NF) $(PYTHON3_CFLAGS) $(ALL_CFLAGS) $(PYTHON3_CFLAGS_EXTRA) -o $@ if_python3.c
 
 objects/if_ruby.o: if_ruby.c
-	$(CCC_NF) $(RUBY_CFLAGS) $(ALL_CFLAGS) -o $@ if_ruby.c
+	$(CCC_NF) $(RUBY_CFLAGS) $(ALL_CFLAGS) $(RUBY_CFLAGS_EXTRA) -o $@ if_ruby.c
 
 objects/if_tcl.o: if_tcl.c
-	$(CCC_NF) $(TCL_CFLAGS) $(ALL_CFLAGS) -o $@ if_tcl.c
+	$(CCC_NF) $(TCL_CFLAGS) $(ALL_CFLAGS) $(TCL_CFLAGS_EXTRA) -o $@ if_tcl.c
 
 objects/indent.o: indent.c
 	$(CCC) -o $@ indent.c
@@ -3459,10 +3460,10 @@
 	$(CCC) -o $@ ops.c
 
 objects/option.o: option.c optiondefs.h
-	$(CCC_NF) $(LUA_CFLAGS) $(PERL_CFLAGS) $(PYTHON_CFLAGS) $(PYTHON3_CFLAGS) $(RUBY_CFLAGS) $(TCL_CFLAGS) $(ALL_CFLAGS) -o $@ option.c
+	$(CCC_NF) $(ALL_IF_CFLAGS) $(ALL_CFLAGS) $(ALL_IF_CFLAGS_EXTRA) -o $@ option.c
 
 objects/optionstr.o: optionstr.c
-	$(CCC_NF) $(LUA_CFLAGS) $(PERL_CFLAGS) $(PYTHON_CFLAGS) $(PYTHON3_CFLAGS) $(RUBY_CFLAGS) $(TCL_CFLAGS) $(ALL_CFLAGS) -o $@ optionstr.c
+	$(CCC_NF) $(ALL_IF_CFLAGS) $(ALL_CFLAGS) $(ALL_IF_CFLAGS_EXTRA) -o $@ optionstr.c
 
 objects/os_qnx.o: os_qnx.c $(VIM_H_DEPENDENCIES)
 	$(CCC) -o $@ os_qnx.c
diff --git a/src/auto/configure b/src/auto/configure
index f13f9bb..cde05d6 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -662,12 +662,14 @@
 NETBEANS_OBJ
 NETBEANS_SRC
 RUBY_LIBS
+RUBY_CFLAGS_EXTRA
 RUBY_CFLAGS
 RUBY_PRO
 RUBY_OBJ
 RUBY_SRC
 vi_cv_path_ruby
 TCL_LIBS
+TCL_CFLAGS_EXTRA
 TCL_CFLAGS
 TCL_PRO
 TCL_OBJ
@@ -675,15 +677,18 @@
 vi_cv_path_tcl
 PYTHON3_OBJ
 PYTHON3_SRC
+PYTHON3_CFLAGS_EXTRA
 PYTHON3_CFLAGS
 PYTHON3_LIBS
 vi_cv_path_python3
 PYTHON_OBJ
 PYTHON_SRC
+PYTHON_CFLAGS_EXTRA
 PYTHON_CFLAGS
 PYTHON_LIBS
 vi_cv_path_python
 PERL_LIBS
+PERL_CFLAGS_EXTRA
 PERL_CFLAGS
 PERL_PRO
 PERL_OBJ
@@ -700,6 +705,7 @@
 MZSCHEME_OBJ
 MZSCHEME_SRC
 vi_cv_path_mzscheme
+LUA_CFLAGS_EXTRA
 LUA_CFLAGS
 LUA_LIBS
 LUA_PRO
@@ -5658,6 +5664,7 @@
 
 
 
+
 fi
 
 
@@ -6273,6 +6280,7 @@
 
 
 
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking --enable-pythoninterp argument" >&5
 $as_echo_n "checking --enable-pythoninterp argument... " >&6; }
 # Check whether --enable-pythoninterp was given.
@@ -6623,6 +6631,7 @@
 
 
 
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking --enable-python3interp argument" >&5
 $as_echo_n "checking --enable-python3interp argument... " >&6; }
 # Check whether --enable-python3interp was given.
@@ -6969,6 +6978,7 @@
 
 
 
+
 if test "$python_ok" = yes && test "$python3_ok" = yes; then
   $as_echo "#define DYNAMIC_PYTHON 1" >>confdefs.h
 
@@ -7549,6 +7559,7 @@
 
 
 
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking --enable-rubyinterp argument" >&5
 $as_echo_n "checking --enable-rubyinterp argument... " >&6; }
 # Check whether --enable-rubyinterp was given.
@@ -7712,6 +7723,7 @@
 
 
 
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking --enable-cscope argument" >&5
 $as_echo_n "checking --enable-cscope argument... " >&6; }
 # Check whether --enable-cscope was given.
diff --git a/src/config.mk.in b/src/config.mk.in
index f55bea6..df09cfe 100644
--- a/src/config.mk.in
+++ b/src/config.mk.in
@@ -41,6 +41,7 @@
 LUA_SRC		= @LUA_SRC@
 LUA_OBJ		= @LUA_OBJ@
 LUA_CFLAGS	= @LUA_CFLAGS@
+LUA_CFLAGS_EXTRA	= @LUA_CFLAGS_EXTRA@
 LUA_PRO		= @LUA_PRO@
 
 MZSCHEME_LIBS	= @MZSCHEME_LIBS@
@@ -60,15 +61,18 @@
 PERL_OBJ	= @PERL_OBJ@
 PERL_PRO	= @PERL_PRO@
 PERL_CFLAGS	= @PERL_CFLAGS@
+PERL_CFLAGS_EXTRA	= @PERL_CFLAGS_EXTRA@
 
 PYTHON_SRC	= @PYTHON_SRC@
 PYTHON_OBJ	= @PYTHON_OBJ@
 PYTHON_CFLAGS	= @PYTHON_CFLAGS@
+PYTHON_CFLAGS_EXTRA	= @PYTHON_CFLAGS_EXTRA@
 PYTHON_LIBS	= @PYTHON_LIBS@
 
 PYTHON3_SRC	= @PYTHON3_SRC@
 PYTHON3_OBJ	= @PYTHON3_OBJ@
 PYTHON3_CFLAGS	= @PYTHON3_CFLAGS@
+PYTHON3_CFLAGS_EXTRA	= @PYTHON3_CFLAGS_EXTRA@
 PYTHON3_LIBS	= @PYTHON3_LIBS@
 
 TCL		= @vi_cv_path_tcl@
@@ -76,6 +80,7 @@
 TCL_OBJ		= @TCL_OBJ@
 TCL_PRO		= @TCL_PRO@
 TCL_CFLAGS	= @TCL_CFLAGS@
+TCL_CFLAGS_EXTRA	= @TCL_CFLAGS_EXTRA@
 TCL_LIBS	= @TCL_LIBS@
 
 NETBEANS_SRC	= @NETBEANS_SRC@
@@ -91,6 +96,7 @@
 RUBY_OBJ	= @RUBY_OBJ@
 RUBY_PRO	= @RUBY_PRO@
 RUBY_CFLAGS	= @RUBY_CFLAGS@
+RUBY_CFLAGS_EXTRA	= @RUBY_CFLAGS_EXTRA@
 RUBY_LIBS	= @RUBY_LIBS@
 
 AWK		= @AWK@
diff --git a/src/configure.ac b/src/configure.ac
index 6fee99c..b5f217c 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -781,6 +781,7 @@
   AC_SUBST(LUA_PRO)
   AC_SUBST(LUA_LIBS)
   AC_SUBST(LUA_CFLAGS)
+  AC_SUBST(LUA_CFLAGS_EXTRA)
 fi
 
 
@@ -1201,6 +1202,7 @@
 AC_SUBST(PERL_OBJ)
 AC_SUBST(PERL_PRO)
 AC_SUBST(PERL_CFLAGS)
+AC_SUBST(PERL_CFLAGS_EXTRA)
 AC_SUBST(PERL_LIBS)
 
 AC_MSG_CHECKING(--enable-pythoninterp argument)
@@ -1433,6 +1435,7 @@
 
 AC_SUBST(PYTHON_LIBS)
 AC_SUBST(PYTHON_CFLAGS)
+AC_SUBST(PYTHON_CFLAGS_EXTRA)
 AC_SUBST(PYTHON_SRC)
 AC_SUBST(PYTHON_OBJ)
 
@@ -1650,6 +1653,7 @@
 
 AC_SUBST(PYTHON3_LIBS)
 AC_SUBST(PYTHON3_CFLAGS)
+AC_SUBST(PYTHON3_CFLAGS_EXTRA)
 AC_SUBST(PYTHON3_SRC)
 AC_SUBST(PYTHON3_OBJ)
 
@@ -1946,6 +1950,7 @@
 AC_SUBST(TCL_OBJ)
 AC_SUBST(TCL_PRO)
 AC_SUBST(TCL_CFLAGS)
+AC_SUBST(TCL_CFLAGS_EXTRA)
 AC_SUBST(TCL_LIBS)
 
 AC_MSG_CHECKING(--enable-rubyinterp argument)
@@ -2050,6 +2055,7 @@
 AC_SUBST(RUBY_OBJ)
 AC_SUBST(RUBY_PRO)
 AC_SUBST(RUBY_CFLAGS)
+AC_SUBST(RUBY_CFLAGS_EXTRA)
 AC_SUBST(RUBY_LIBS)
 
 AC_MSG_CHECKING(--enable-cscope argument)
diff --git a/src/if_ruby.c b/src/if_ruby.c
index 0d7eaf2..07c817d 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -73,35 +73,40 @@
 # if RUBY_VERSION >= 19
 // Ruby 1.9 defines a number of static functions which use rb_num2long and
 // rb_int2big
-#  define rb_num2long rb_num2long_stub
-#  define rb_int2big rb_int2big_stub
+#  define rb_num2long	rb_num2long_stub
+#  define rb_int2big	rb_int2big_stub
 
 #  if RUBY_VERSION >= 30 || VIM_SIZEOF_INT < VIM_SIZEOF_LONG
 // Ruby 1.9 defines a number of static functions which use rb_fix2int and
 // rb_num2int if VIM_SIZEOF_INT < VIM_SIZEOF_LONG (64bit)
-#   define rb_fix2int rb_fix2int_stub
-#   define rb_num2int rb_num2int_stub
+#   define rb_fix2int	rb_fix2int_stub
+#   define rb_num2int	rb_num2int_stub
 #  endif
 # endif
 
 # if RUBY_VERSION == 21
 // Ruby 2.1 adds new GC called RGenGC and RARRAY_PTR uses
 // rb_gc_writebarrier_unprotect_promoted if USE_RGENGC
-#  define rb_gc_writebarrier_unprotect_promoted rb_gc_writebarrier_unprotect_promoted_stub
+#  define rb_gc_writebarrier_unprotect_promoted	rb_gc_writebarrier_unprotect_promoted_stub
 # endif
 
 # if RUBY_VERSION >= 22
-#  define rb_gc_writebarrier_unprotect rb_gc_writebarrier_unprotect_stub
+#  define rb_gc_writebarrier_unprotect	rb_gc_writebarrier_unprotect_stub
 # endif
 
 # if RUBY_VERSION >= 26
-#  define rb_ary_detransient rb_ary_detransient_stub
+#  define rb_ary_detransient	rb_ary_detransient_stub
 # endif
 
 # if RUBY_VERSION >= 30
-#  define rb_check_type rb_check_type_stub
-#  define rb_num2uint rb_num2uint_stub
-#  define ruby_malloc_size_overflow ruby_malloc_size_overflow_stub
+#  define rb_check_type			rb_check_type_stub
+#  define rb_num2uint			rb_num2uint_stub
+#  define ruby_malloc_size_overflow	ruby_malloc_size_overflow_stub
+# endif
+
+# if RUBY_VERSION >= 31
+#  define rb_debug_rstring_null_ptr	rb_debug_rstring_null_ptr_stub
+#  define rb_unexpected_type		rb_unexpected_type_stub
 # endif
 
 #endif  // ifdef DYNAMIC_RUBY
@@ -173,6 +178,14 @@
 # undef HAVE_DUP
 #endif
 
+// Avoid redefining TRUE/FALSE in vterm.h.
+#ifdef TRUE
+# undef TRUE
+#endif
+#ifdef FALSE
+# undef FALSE
+#endif
+
 #include "vim.h"
 #include "version.h"
 
@@ -411,6 +424,9 @@
 # else
 static VALUE (*dll_rb_data_object_alloc) (VALUE, void*, RUBY_DATA_FUNC, RUBY_DATA_FUNC);
 # endif
+# if RUBY_VERSION >= 31
+static void (*dll_rb_debug_rstring_null_ptr) (const char*);
+# endif
 static VALUE (*dll_rb_define_class_under) (VALUE, const char*, VALUE);
 static void (*dll_rb_define_const) (VALUE,const char*,VALUE);
 static void (*dll_rb_define_global_function) (const char*,VALUE(*)(),int);
@@ -485,6 +501,9 @@
 static int (*dll_rb_w32_snprintf)(char*, size_t, const char*, ...);
 #  endif
 # endif
+# if RUBY_VERSION >= 31
+static void (*dll_rb_unexpected_type) (VALUE, int) ATTRIBUTE_NORETURN;
+# endif
 # if RUBY_VERSION >= 18
 static char * (*dll_rb_string_value_ptr) (volatile VALUE*);
 static VALUE (*dll_rb_float_new) (double);
@@ -629,6 +648,18 @@
     dll_ruby_malloc_size_overflow(x, y);
 }
 #  endif
+#  if RUBY_VERSION >= 31
+    void
+rb_debug_rstring_null_ptr_stub(const char *func)
+{
+    dll_rb_debug_rstring_null_ptr(func);
+}
+    void
+rb_unexpected_type_stub(VALUE self, int t)
+{
+    dll_rb_unexpected_type(self, t);
+}
+#  endif
 # endif // ifndef PROTO
 
 static HINSTANCE hinstRuby = NULL; // Instance of ruby.dll
@@ -672,6 +703,9 @@
 # else
     {"rb_data_object_alloc", (RUBY_PROC*)&dll_rb_data_object_alloc},
 # endif
+# if RUBY_VERSION >= 31
+    {"rb_debug_rstring_null_ptr", (RUBY_PROC*)&dll_rb_debug_rstring_null_ptr},
+# endif
     {"rb_define_class_under", (RUBY_PROC*)&dll_rb_define_class_under},
     {"rb_define_const", (RUBY_PROC*)&dll_rb_define_const},
     {"rb_define_global_function", (RUBY_PROC*)&dll_rb_define_global_function},
@@ -745,6 +779,9 @@
     {"rb_w32_snprintf", (RUBY_PROC*)&dll_rb_w32_snprintf},
 #  endif
 # endif
+# if RUBY_VERSION >= 31
+    {"rb_unexpected_type", (RUBY_PROC*)&dll_rb_unexpected_type},
+# endif
 # if RUBY_VERSION >= 18
     {"rb_string_value_ptr", (RUBY_PROC*)&dll_rb_string_value_ptr},
 #  if RUBY_VERSION <= 19
diff --git a/src/version.c b/src/version.c
index 96359c1..6c8bced 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3922,
+/**/
     3921,
 /**/
     3920,
diff --git a/src/vim.h b/src/vim.h
index 55bb7cd..21832ab 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2177,13 +2177,15 @@
 #endif
 
 #if defined(__GNUC__) || defined(__clang__)
-# define likely(x)      __builtin_expect((x), 1)
-# define unlikely(x)    __builtin_expect((x), 0)
-# define ATTRIBUTE_COLD __attribute__((cold))
+# define likely(x)		__builtin_expect((x), 1)
+# define unlikely(x)		__builtin_expect((x), 0)
+# define ATTRIBUTE_COLD		__attribute__((cold))
+# define ATTRIBUTE_NORETURN	__attribute__((noreturn))
 #else
-# define unlikely(x)  (x)
-# define likely(x)    (x)
+# define unlikely(x)	(x)
+# define likely(x)	(x)
 # define ATTRIBUTE_COLD
+# define ATTRIBUTE_NORETURN
 #endif
 
 typedef enum {