1# $NetBSD: varmod-loop-delete.mk,v 1.2 2021/12/05 15:51:33 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. 19EVAL:= ${VAR} 20.if ${EVAL} != " rest of the value" 21. error 22.endif 23 24VAR= ${:U:@VAR@@} rest of the value 25all: .PHONY 26 # In the command that is associated with a target, the scope is the 27 # one from the target. That scope only contains a few variables like 28 # '.TARGET', '.ALLSRC', '.IMPSRC'. Make does not expect that these 29 # variables get modified from the outside. 30 # 31 # There is no variable named 'VAR' in the local scope, so nothing 32 # happens. 33 : $@: '${VAR}' 34