1# $NetBSD: cond-undef-lint.mk,v 1.3 2020/11/15 14:58:14 rillig Exp $ 2# 3# Tests for defined and undefined variables in .if conditions, in lint mode. 4# 5# As of 2020-09-14, lint mode contains experimental code for printing 6# accurate error messages in case of undefined variables, instead of the 7# wrong "Malformed condition". 8# 9# See also: 10# opt-debug-lint.mk 11 12.MAKEFLAGS: -dL 13 14# DEF is defined, UNDEF is not. 15DEF= defined 16 17# An expression based on a defined variable is fine. 18.if !${DEF} 19. error 20.endif 21 22# Since the condition fails to evaluate, neither of the branches is taken. 23.if ${UNDEF} 24. error 25.else 26. error 27.endif 28 29# The variable name depends on the undefined variable, which is probably a 30# mistake. The variable UNDEF, as used here, can be easily turned into 31# an expression that is always defined, using the :U modifier. 32# 33# The outer expression does not generate an error message since there was 34# already an error evaluating this variable's name. 35# 36# TODO: Suppress the error message "Variable VAR. is undefined". That part 37# of the expression must not be evaluated at all. 38.if ${VAR.${UNDEF}} 39. error 40.else 41. error 42.endif 43 44# The variable VAR.defined is not defined and thus generates an error message. 45# 46# TODO: This pattern looks a lot like CFLAGS.${OPSYS}, which is at least 47# debatable. Or would any practical use of CFLAGS.${OPSYS} be via an indirect 48# expression, as in the next example? 49.if ${VAR.${DEF}} 50. error 51.else 52. error 53.endif 54 55 56# Variables that are referenced indirectly may be undefined in a condition. 57# 58# A practical example for this is CFLAGS, which consists of CWARNS, COPTS 59# and a few others. Just because these nested variables are not defined, 60# this does not make the condition invalid. 61# 62# The crucial point is that at the point where the variable appears in the 63# condition, there is no way to influence the definedness of the nested 64# variables. In particular, there is no modifier that would turn undefined 65# nested variables into empty strings, as an equivalent to the :U modifier. 66INDIRECT= ${NESTED_UNDEF} ${NESTED_DEF} 67NESTED_DEF= nested-defined 68 69# Since NESTED_UNDEF is not controllable at this point, it must not generate 70# an error message, and it doesn't do so, since 2020-09-14. 71.if !${INDIRECT} 72. error 73.endif 74