diff --git a/src/proto/vim9compile.pro b/src/proto/vim9compile.pro
index 6905fc2..b22bf98 100644
--- a/src/proto/vim9compile.pro
+++ b/src/proto/vim9compile.pro
@@ -9,6 +9,7 @@
 char_u *to_name_const_end(char_u *arg);
 int assignment_len(char_u *p, int *heredoc);
 void compile_def_function(ufunc_T *ufunc, int set_return_type);
+void delete_instr(isn_T *isn);
 void delete_def_function(ufunc_T *ufunc);
 void free_def_functions(void);
 /* vim: set ft=c : */
diff --git a/src/scriptfile.c b/src/scriptfile.c
index 838d5f6..55b1ddd 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1526,6 +1526,7 @@
 	vim_free(si->sn_vars);
 
 	vim_free(si->sn_name);
+	free_imports(i);
 	free_string_option(si->sn_save_cpo);
 #  ifdef FEAT_PROFILE
 	ga_clear(&si->sn_prl_ga);
diff --git a/src/structs.h b/src/structs.h
index 76d45ea..ff32cb2 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1308,6 +1308,7 @@
     int		cb_free_name;	    // cb_name was allocated
 } callback_T;
 
+typedef struct isn_S isn_T;	    // instruction
 typedef struct dfunc_S dfunc_T;	    // :def function
 
 typedef struct jobvar_S job_T;
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index c5dd1d3..a02855d 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -942,6 +942,16 @@
   assert_equal('1_3_', result)
 enddef
 
+def Test_interrupt_loop()
+  let x = 0
+  while 1
+    x += 1
+    if x == 100
+      feedkeys("\<C-C>", 'L')
+    endif
+  endwhile
+enddef
+
 def Test_substitute_cmd()
   new
   setline(1, 'something')
@@ -964,4 +974,24 @@
   delete('Xvim9lines')
 enddef
 
+def Test_redef_failure()
+  call writefile(['def Func0(): string',  'return "Func0"', 'enddef'], 'Xdef')
+  so Xdef
+  call writefile(['def Func1(): string',  'return "Func1"', 'enddef'], 'Xdef')
+  so Xdef
+  call writefile(['def! Func0(): string', 'enddef'], 'Xdef')
+  call assert_fails('so Xdef', 'E1027:')
+  call writefile(['def Func2(): string',  'return "Func2"', 'enddef'], 'Xdef')
+  so Xdef
+  call delete('Xdef')
+
+  call assert_equal(0, Func0())
+  call assert_equal('Func1', Func1())
+  call assert_equal('Func2', Func2())
+
+  delfunc! Func0
+  delfunc! Func1
+  delfunc! Func2
+enddef
+
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker
diff --git a/src/version.c b/src/version.c
index 81fff38..26939bb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    419,
+/**/
     418,
 /**/
     417,
diff --git a/src/vim9.h b/src/vim9.h
index 38286b3..ffa09a7 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -203,7 +203,7 @@
 /*
  * Instruction
  */
-typedef struct {
+struct isn_S {
     isntype_T	isn_type;
     int		isn_lnum;
     union {
@@ -231,7 +231,7 @@
 	loadstore_T	    loadstore;
 	script_T	    script;
     } isn_arg;
-} isn_T;
+};
 
 /*
  * Info about a function defined with :def.  Used in "def_functions".
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 38b904d..f768fc7 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -129,6 +129,7 @@
 static int compile_expr1(char_u **arg,  cctx_T *cctx);
 static int compile_expr2(char_u **arg,  cctx_T *cctx);
 static int compile_expr3(char_u **arg,  cctx_T *cctx);
+static void delete_def_function_contents(dfunc_T *dfunc);
 
 /*
  * Lookup variable "name" in the local scope and return the index.
@@ -1306,6 +1307,36 @@
 }
 
 /*
+ * Remove local variables above "new_top".
+ */
+    static void
+unwind_locals(cctx_T *cctx, int new_top)
+{
+    if (cctx->ctx_locals.ga_len > new_top)
+    {
+	int	idx;
+	lvar_T	*lvar;
+
+	for (idx = new_top; idx < cctx->ctx_locals.ga_len; ++idx)
+	{
+	    lvar = ((lvar_T *)cctx->ctx_locals.ga_data) + idx;
+	    vim_free(lvar->lv_name);
+	}
+    }
+    cctx->ctx_locals.ga_len = new_top;
+}
+
+/*
+ * Free all local variables.
+ */
+    static void
+free_local(cctx_T *cctx)
+{
+    unwind_locals(cctx, 0);
+    ga_clear(&cctx->ctx_locals);
+}
+
+/*
  * Skip over a type definition and return a pointer to just after it.
  */
     char_u *
@@ -1672,6 +1703,23 @@
 }
 
 /*
+ * Free all imported variables.
+ */
+    static void
+free_imported(cctx_T *cctx)
+{
+    int idx;
+
+    for (idx = 0; idx < cctx->ctx_imports.ga_len; ++idx)
+    {
+	imported_T *import = ((imported_T *)cctx->ctx_imports.ga_data) + idx;
+
+	vim_free(import->imp_name);
+    }
+    ga_clear(&cctx->ctx_imports);
+}
+
+/*
  * Generate an instruction to load script-local variable "name".
  */
     static int
@@ -2127,7 +2175,10 @@
     // Get the funcref in "rettv".
     if (get_lambda_tv(arg, &rettv, TRUE) == FAIL)
 	return FAIL;
+
     ufunc = rettv.vval.v_partial->pt_func;
+    ++ufunc->uf_refcount;
+    clear_tv(&rettv);
 
     // The function will have one line: "return {expr}".
     // Compile it into instructions.
@@ -2169,10 +2220,12 @@
 	return FAIL;
     }
 
-    // The function will have one line: "return {expr}".
-    // Compile it into instructions.
     ufunc = rettv.vval.v_partial->pt_func;
     ++ufunc->uf_refcount;
+    clear_tv(&rettv);
+
+    // The function will have one line: "return {expr}".
+    // Compile it into instructions.
     compile_def_function(ufunc, TRUE);
 
     // compile the arguments
@@ -2181,7 +2234,6 @@
 	// call the compiled function
 	ret = generate_CALL(cctx, ufunc, argcount);
 
-    clear_tv(&rettv);
     return ret;
 }
 
@@ -3398,7 +3450,6 @@
 	{
 	    int	    cc;
 	    long	    numval;
-	    char_u	    *stringval = NULL;
 
 	    dest = dest_option;
 	    if (cmdidx == CMD_const)
@@ -3420,7 +3471,7 @@
 	    }
 	    cc = *p;
 	    *p = NUL;
-	    opt_type = get_option_value(arg + 1, &numval, &stringval, opt_flags);
+	    opt_type = get_option_value(arg + 1, &numval, NULL, opt_flags);
 	    *p = cc;
 	    if (opt_type == -3)
 	    {
@@ -4217,7 +4268,7 @@
 	emsg(_(e_elseif_without_if));
 	return NULL;
     }
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
 
     if (cctx->ctx_skip == MAYBE)
     {
@@ -4265,7 +4316,7 @@
 	emsg(_(e_else_without_if));
 	return NULL;
     }
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
 
     // jump from previous block to the end, unless the else block is empty
     if (cctx->ctx_skip == MAYBE)
@@ -4307,7 +4358,7 @@
     }
     ifscope = &scope->se_u.se_if;
     cctx->ctx_scope = scope->se_outer;
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
 
     if (scope->se_u.se_if.is_if_label >= 0)
     {
@@ -4435,7 +4486,7 @@
     }
     forscope = &scope->se_u.se_for;
     cctx->ctx_scope = scope->se_outer;
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
 
     // At end of ":for" scope jump back to the FOR instruction.
     generate_JUMP(cctx, JUMP_ALWAYS, forscope->fs_top_label);
@@ -4506,7 +4557,7 @@
 	return NULL;
     }
     cctx->ctx_scope = scope->se_outer;
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
 
     // At end of ":for" scope jump back to the FOR instruction.
     generate_JUMP(cctx, JUMP_ALWAYS, scope->se_u.se_while.ws_top_label);
@@ -4599,7 +4650,7 @@
     scope_T	*scope = cctx->ctx_scope;
 
     cctx->ctx_scope = scope->se_outer;
-    cctx->ctx_locals.ga_len = scope->se_local_count;
+    unwind_locals(cctx, scope->se_local_count);
     vim_free(scope);
 }
 
@@ -4942,9 +4993,11 @@
 
     if (ufunc->uf_dfunc_idx >= 0)
     {
-	// redefining a function that was compiled before
+	// Redefining a function that was compiled before.
 	dfunc = ((dfunc_T *)def_functions.ga_data) + ufunc->uf_dfunc_idx;
-	dfunc->df_deleted = FALSE;
+
+	// Free old instructions.
+	delete_def_function_contents(dfunc);
     }
     else
     {
@@ -5305,6 +5358,7 @@
 	generate_instr(&cctx, ISN_RETURN);
     }
 
+    dfunc->df_deleted = FALSE;
     dfunc->df_instr = instr->ga_data;
     dfunc->df_instr_count = instr->ga_len;
     dfunc->df_varcount = cctx.ctx_max_local;
@@ -5314,27 +5368,35 @@
 erret:
     if (ret == FAIL)
     {
+	int idx;
+
+	for (idx = 0; idx < instr->ga_len; ++idx)
+	    delete_instr(((isn_T *)instr->ga_data) + idx);
 	ga_clear(instr);
+
 	ufunc->uf_dfunc_idx = -1;
-	--def_functions.ga_len;
+	if (!dfunc->df_deleted)
+	    --def_functions.ga_len;
+
+	// Don't execute this function body.
+	ga_clear_strings(&ufunc->uf_lines);
+
 	if (errormsg != NULL)
 	    emsg(errormsg);
 	else if (called_emsg == called_emsg_before)
 	    emsg(_("E1028: compile_def_function failed"));
-
-	// don't execute this function body
-	ufunc->uf_lines.ga_len = 0;
     }
 
     current_sctx = save_current_sctx;
+    free_imported(&cctx);
+    free_local(&cctx);
     ga_clear(&cctx.ctx_type_stack);
-    ga_clear(&cctx.ctx_locals);
 }
 
 /*
  * Delete an instruction, free what it contains.
  */
-    static void
+    void
 delete_instr(isn_T *isn)
 {
     switch (isn->isn_type)
@@ -5443,32 +5505,57 @@
 }
 
 /*
+ * Free all instructions for "dfunc".
+ */
+    static void
+delete_def_function_contents(dfunc_T *dfunc)
+{
+    int idx;
+
+    ga_clear(&dfunc->df_def_args_isn);
+
+    if (dfunc->df_instr != NULL)
+    {
+	for (idx = 0; idx < dfunc->df_instr_count; ++idx)
+	    delete_instr(dfunc->df_instr + idx);
+	VIM_CLEAR(dfunc->df_instr);
+    }
+
+    dfunc->df_deleted = TRUE;
+}
+
+/*
  * When a user function is deleted, delete any associated def function.
  */
     void
 delete_def_function(ufunc_T *ufunc)
 {
-    int idx;
-
     if (ufunc->uf_dfunc_idx >= 0)
     {
 	dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data)
 							 + ufunc->uf_dfunc_idx;
-	ga_clear(&dfunc->df_def_args_isn);
 
-	for (idx = 0; idx < dfunc->df_instr_count; ++idx)
-	    delete_instr(dfunc->df_instr + idx);
-	VIM_CLEAR(dfunc->df_instr);
-
-	dfunc->df_deleted = TRUE;
+	delete_def_function_contents(dfunc);
     }
 }
 
 #if defined(EXITFREE) || defined(PROTO)
+/*
+ * Free all functions defined with ":def".
+ */
     void
 free_def_functions(void)
 {
-    vim_free(def_functions.ga_data);
+    int idx;
+
+    for (idx = 0; idx < def_functions.ga_len; ++idx)
+    {
+	dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data) + idx;
+
+	delete_def_function_contents(dfunc);
+    }
+
+    ga_clear(&def_functions);
 }
 #endif
 
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 8c8bf88..33b6430 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -283,6 +283,7 @@
 	// that was defined later: we can call it directly next time.
 	if (iptr != NULL)
 	{
+	    delete_instr(iptr);
 	    iptr->isn_type = ISN_DCALL;
 	    iptr->isn_arg.dfunc.cdf_idx = ufunc->uf_dfunc_idx;
 	    iptr->isn_arg.dfunc.cdf_argcount = argcount;
@@ -480,11 +481,21 @@
     for (;;)
     {
 	isn_T	    *iptr;
-	trycmd_T    *trycmd = NULL;
+
+	veryfast_breakcheck();
+	if (got_int)
+	{
+	    // Turn CTRL-C into an exception.
+	    got_int = FALSE;
+	    if (throw_exception("Vim:Interrupt", ET_INTERRUPT, NULL) != FAIL)
+		goto failed;
+	    did_throw = TRUE;
+	}
 
 	if (did_throw && !ectx.ec_in_catch)
 	{
 	    garray_T	*trystack = &ectx.ec_trystack;
+	    trycmd_T    *trycmd = NULL;
 
 	    // An exception jumps to the first catch, finally, or returns from
 	    // the current function.
@@ -782,8 +793,9 @@
 	    // store $ENV
 	    case ISN_STOREENV:
 		--ectx.ec_stack.ga_len;
-		vim_setenv_ext(iptr->isn_arg.string,
-					       tv_get_string(STACK_TV_BOT(0)));
+		tv = STACK_TV_BOT(0);
+		vim_setenv_ext(iptr->isn_arg.string, tv_get_string(tv));
+		clear_tv(tv);
 		break;
 
 	    // store @r
@@ -1038,6 +1050,7 @@
 	    case ISN_RETURN:
 		{
 		    garray_T	*trystack = &ectx.ec_trystack;
+		    trycmd_T    *trycmd = NULL;
 
 		    if (trystack->ga_len > 0)
 			trycmd = ((trycmd_T *)trystack->ga_data)
@@ -1146,6 +1159,8 @@
 	    // start of ":try" block
 	    case ISN_TRY:
 		{
+		    trycmd_T    *trycmd = NULL;
+
 		    if (ga_grow(&ectx.ec_trystack, 1) == FAIL)
 			goto failed;
 		    trycmd = ((trycmd_T *)ectx.ec_trystack.ga_data)
@@ -1180,7 +1195,7 @@
 
 		    if (trystack->ga_len > 0)
 		    {
-			trycmd = ((trycmd_T *)trystack->ga_data)
+			trycmd_T    *trycmd = ((trycmd_T *)trystack->ga_data)
 							+ trystack->ga_len - 1;
 			trycmd->tcd_caught = TRUE;
 		    }
@@ -1196,6 +1211,8 @@
 
 		    if (trystack->ga_len > 0)
 		    {
+			trycmd_T    *trycmd = NULL;
+
 			--trystack->ga_len;
 			--trylevel;
 			trycmd = ((trycmd_T *)trystack->ga_data)
@@ -1677,6 +1694,7 @@
     for (idx = 0; idx < ectx.ec_stack.ga_len; ++idx)
 	clear_tv(STACK_TV(idx));
     vim_free(ectx.ec_stack.ga_data);
+    vim_free(ectx.ec_trystack.ga_data);
     return ret;
 }
 
diff --git a/src/vim9script.c b/src/vim9script.c
index ce5cfec..e74a7b9 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -119,11 +119,13 @@
 
     for (idx = 0; idx < si->sn_imports.ga_len; ++idx)
     {
-	imported_T *imp = ((imported_T *)si->sn_imports.ga_data + idx);
+	imported_T *imp = ((imported_T *)si->sn_imports.ga_data) + idx;
 
 	vim_free(imp->imp_name);
     }
     ga_clear(&si->sn_imports);
+    ga_clear(&si->sn_var_vals);
+    ga_clear(&si->sn_type_list);
 }
 
 /*