patch 8.2.0488: Vim9: compiling can break when using a lambda inside :def

Problem:    Vim9: Compiling can break when using a lambda inside :def.
Solution:   Do not keep a pointer to the dfunc_T for longer time.

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    488,
 /**/
     487,
 /**/

src/vim9.h

@@ -257,7 +257,7 @@ struct dfunc_S {
 // Functions defined with :def are stored in this growarray.
 // They are never removed, so that they can be found by index.
 // Deleted functions have the df_deleted flag set.
-garray_T def_functions = {0, 0, sizeof(dfunc_T), 200, NULL};
+garray_T def_functions = {0, 0, sizeof(dfunc_T), 50, NULL};
 #else
 extern garray_T def_functions;
 #endif

src/vim9compile.c

@@ -5029,11 +5029,12 @@ compile_execute(char_u *arg, cctx_T *cctx)
  * Adds the function to "def_functions".
  * When "set_return_type" is set then set ufunc->uf_ret_type to the type of the
  * return statement (used for lambda).
+ * This can be used recursively through compile_lambda(), which may reallocate
+ * "def_functions".
  */
     void
 compile_def_function(ufunc_T *ufunc, int set_return_type)
 {
-    dfunc_T	*dfunc;
     char_u	*line = NULL;
     char_u	*p;
     exarg_T	ea;
@@ -5046,25 +5047,29 @@ compile_def_function(ufunc_T *ufunc, int set_return_type)
     sctx_T	save_current_sctx = current_sctx;
     int		emsg_before = called_emsg;
 
-    if (ufunc->uf_dfunc_idx >= 0)
     {
-	// Redefining a function that was compiled before.
+	dfunc_T	*dfunc;  // may be invalidated by compile_lambda()
-	dfunc = ((dfunc_T *)def_functions.ga_data) + ufunc->uf_dfunc_idx;
 
-	// Free old instructions.
+	if (ufunc->uf_dfunc_idx >= 0)
-	delete_def_function_contents(dfunc);
+	{
-    }
+	    // Redefining a function that was compiled before.
-    else
+	    dfunc = ((dfunc_T *)def_functions.ga_data) + ufunc->uf_dfunc_idx;
-    {
+
-	// Add the function to "def_functions".
+	    // Free old instructions.
-	if (ga_grow(&def_functions, 1) == FAIL)
+	    delete_def_function_contents(dfunc);
-	    return;
+	}
-	dfunc = ((dfunc_T *)def_functions.ga_data) + def_functions.ga_len;
+	else
-	vim_memset(dfunc, 0, sizeof(dfunc_T));
+	{
-	dfunc->df_idx = def_functions.ga_len;
+	    // Add the function to "def_functions".
-	ufunc->uf_dfunc_idx = dfunc->df_idx;
+	    if (ga_grow(&def_functions, 1) == FAIL)
-	dfunc->df_ufunc = ufunc;
+		return;
-	++def_functions.ga_len;
+	    dfunc = ((dfunc_T *)def_functions.ga_data) + def_functions.ga_len;
+	    vim_memset(dfunc, 0, sizeof(dfunc_T));
+	    dfunc->df_idx = def_functions.ga_len;
+	    ufunc->uf_dfunc_idx = dfunc->df_idx;
+	    dfunc->df_ufunc = ufunc;
+	    ++def_functions.ga_len;
+	}
     }
 
     vim_memset(&cctx, 0, sizeof(cctx));
@@ -5414,10 +5419,14 @@ compile_def_function(ufunc_T *ufunc, int set_return_type)
 	generate_instr(&cctx, ISN_RETURN);
     }
 
-    dfunc->df_deleted = FALSE;
+    {
-    dfunc->df_instr = instr->ga_data;
+	dfunc_T	*dfunc = ((dfunc_T *)def_functions.ga_data)
-    dfunc->df_instr_count = instr->ga_len;
+							 + ufunc->uf_dfunc_idx;
-    dfunc->df_varcount = cctx.ctx_max_local;
+	dfunc->df_deleted = FALSE;
+	dfunc->df_instr = instr->ga_data;
+	dfunc->df_instr_count = instr->ga_len;
+	dfunc->df_varcount = cctx.ctx_max_local;
+    }
 
     ret = OK;
 
@@ -5425,6 +5434,8 @@ erret:
     if (ret == FAIL)
     {
 	int idx;
+	dfunc_T	*dfunc = ((dfunc_T *)def_functions.ga_data)
+							 + ufunc->uf_dfunc_idx;
 
 	for (idx = 0; idx < instr->ga_len; ++idx)
 	    delete_instr(((isn_T *)instr->ga_data) + idx);