diff options
Diffstat (limited to 'unit-tests/cond-token-var.mk')
| -rw-r--r-- | unit-tests/cond-token-var.mk | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/unit-tests/cond-token-var.mk b/unit-tests/cond-token-var.mk index 6e55bd2d552d..30eba87ad4d2 100644 --- a/unit-tests/cond-token-var.mk +++ b/unit-tests/cond-token-var.mk @@ -1,6 +1,17 @@ -# $NetBSD: cond-token-var.mk,v 1.4 2020/10/24 08:46:08 rillig Exp $ +# $NetBSD: cond-token-var.mk,v 1.5 2020/11/15 14:58:14 rillig Exp $ # -# Tests for variables in .if conditions. +# Tests for variable expressions in .if conditions. +# +# Note the fine distinction between a variable and a variable expression. +# A variable has a name and a value. To access the value, one writes a +# variable expression of the form ${VAR}. This is a simple variable +# expression. Variable expressions can get more complicated by adding +# variable modifiers such as in ${VAR:Mpattern}. +# +# XXX: Strictly speaking, variable modifiers should be called expression +# modifiers instead since they only modify the expression, not the variable. +# Well, except for the assignment modifiers, these do indeed change the value +# of the variable. DEF= defined @@ -12,11 +23,13 @@ DEF= defined .endif # A variable that appears on the left-hand side must be defined. +# The following line thus generates a parse error. .if ${UNDEF} == ${DEF} . error .endif # A variable that appears on the right-hand side must be defined. +# The following line thus generates a parse error. .if ${DEF} == ${UNDEF} . error .endif @@ -25,10 +38,11 @@ DEF= defined .if ${DEF} .endif -# An undefined variable generates a warning. +# An undefined variable on its own generates a parse error. .if ${UNDEF} .endif -# The :U modifier turns an undefined variable into an ordinary expression. +# The :U modifier turns an undefined expression into a defined expression. +# Since the expression is defined now, it doesn't generate any parse error. .if ${UNDEF:U} .endif |