Module Name: src
Committed By: rillig
Date: Tue Aug 25 18:59:30 UTC 2020
Modified Files:
src/usr.bin/make/unit-tests: varmod-assign.mk
Log Message:
make(1): explain the varmod-assign test
I have no idea why I added the mod-assign-nested test. It is completely
boring and doesn't provide any insight.
To generate a diff of this commit:
cvs rdiff -u -r1.2 -r1.3 src/usr.bin/make/unit-tests/varmod-assign.mk
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/make/unit-tests/varmod-assign.mk
diff -u src/usr.bin/make/unit-tests/varmod-assign.mk:1.2 src/usr.bin/make/unit-tests/varmod-assign.mk:1.3
--- src/usr.bin/make/unit-tests/varmod-assign.mk:1.2 Sun Aug 16 12:48:55 2020
+++ src/usr.bin/make/unit-tests/varmod-assign.mk Tue Aug 25 18:59:30 2020
@@ -1,4 +1,4 @@
-# $NetBSD: varmod-assign.mk,v 1.2 2020/08/16 12:48:55 rillig Exp $
+# $NetBSD: varmod-assign.mk,v 1.3 2020/08/25 18:59:30 rillig Exp $
#
# Tests for the obscure ::= variable modifiers, which perform variable
# assignments during evaluation, just like the = operator in C.
@@ -7,17 +7,41 @@ all: mod-assign
all: mod-assign-nested
mod-assign:
+ # The ::?= modifier applies the ?= assignment operator 3 times.
+ # The ?= operator only has an effect for the first time, therefore
+ # the variable FIRST ends up with the value 1.
@echo $@: ${1 2 3:L:@i@${FIRST::?=$i}@} first=${FIRST}.
+
+ # The ::= modifier applies the = assignment operator 3 times.
+ # The = operator overwrites the previous value, therefore the
+ # variable LAST ends up with the value 3.
@echo $@: ${1 2 3:L:@i@${LAST::=$i}@} last=${LAST}.
+
+ # The ::+= modifier applies the += assignment operator 3 times.
+ # The += operator appends 3 times to the variable, therefore
+ # the variable APPENDED ends up with the value "1 2 3".
@echo $@: ${1 2 3:L:@i@${APPENDED::+=$i}@} appended=${APPENDED}.
+
+ # The ::!= modifier applies the != assignment operator 3 times.
+ # The side effects of the shell commands are visible in the output.
+ # Just as with the ::= modifier, the last value is stored in the
+ # RAN variable.
@echo $@: ${echo.1 echo.2 echo.3:L:@i@${RAN::!=${i:C,.*,&; & 1>\&2,:S,., ,g}}@} ran:${RAN}.
+
# The assignments happen in the global scope and thus are
# preserved even after the shell command has been run.
@echo $@: global: ${FIRST:Q}, ${LAST:Q}, ${APPENDED:Q}, ${RAN:Q}.
mod-assign-nested:
+ # The condition "1" is true, therefore THEN1 gets assigned a value,
+ # and IT1 as well. Nothing surprising here.
@echo $@: ${1:?${THEN1::=then1${IT1::=t1}}:${ELSE1::=else1${IE1::=e1}}}${THEN1}${ELSE1}${IT1}${IE1}
+
+ # The condition "0" is false, therefore ELSE1 gets assigned a value,
+ # and IE1 as well. Nothing surprising here as well.
@echo $@: ${0:?${THEN2::=then2${IT2::=t2}}:${ELSE2::=else2${IE2::=e2}}}${THEN2}${ELSE2}${IT2}${IE2}
+
+ # The same effects happen when the variables are defined elsewhere.
@echo $@: ${SINK3:Q}
@echo $@: ${SINK4:Q}
SINK3:= ${1:?${THEN3::=then3${IT3::=t3}}:${ELSE3::=else3${IE3::=e3}}}${THEN3}${ELSE3}${IT3}${IE3}
