Add -Wall,-Werror compiler flags

src/builtins.c

@@ -31,6 +31,9 @@ LISP_FUNC_1(ucl_builtin_type, scope, arg) {
             assert(0);
             return NULL;
     }
+
+    assert(0);
+    return ucl_error_create("Unreachable error in 'ucl_builtin_type'");
 }
 
 LISP_FUNC_1(ucl_builtin_error, scope, arg) {
@@ -147,7 +150,7 @@ LISP_FUNC_2(ucl_builtin_concat, scope, arg0, arg1) {
     }
 
     int len = strlen(arg0->string) + strlen(arg1->string);
-    char *outstr = malloc(strlen(arg0->string) + strlen(arg1->string));
+    char *outstr = malloc(len);
     outstr[0] = '\0';
     strcat(outstr, arg0->string);
     strcat(outstr, arg1->string);