1# $NetBSD: varmod-loop-delete.mk,v 1.3 2023/06/01 20:56:35 rillig Exp $ 2# 3# Tests for the variable modifier ':@', which as a side effect allows to 4# delete an arbitrary variable. 5 6# A side effect of the modifier ':@' is that the loop variable is created as 7# an actual variable in the current evaluation scope (Command/Global/target), 8# and at the end of the loop, this variable is deleted. Since var.c 1.204 9# from 2016-02-18 and before var.c 1.963 from 2021-12-05, a variable could be 10# deleted while it was in use, leading to a use-after-free bug. 11# 12# See Var_Parse, comment 'the value of the variable must not change'. 13 14# Set up the variable that deletes itself when it is evaluated. 15VAR= ${:U:@VAR@@} rest of the value 16 17# In an assignment, the scope is 'Global'. Since the variable 'VAR' is 18# defined in the global scope, it deletes itself. 19# expect+1: Cannot delete variable "VAR" while it is used 20EVAL:= ${VAR} 21.if ${EVAL} != " rest of the value" 22. error 23.endif 24 25VAR= ${:U:@VAR@@} rest of the value 26all: .PHONY 27 # In the command that is associated with a target, the scope is the 28 # one from the target. That scope only contains a few variables like 29 # '.TARGET', '.ALLSRC', '.IMPSRC'. Make does not expect that these 30 # variables get modified from the outside. 31 # 32 # There is no variable named 'VAR' in the local scope, so nothing 33 # happens. 34 : $@: '${VAR}' 35