Module Name: src
Committed By: rillig
Date: Sat Mar 4 21:15:30 UTC 2023
Modified Files:
src/usr.bin/make/unit-tests: cond-func-empty.exp cond-func-empty.mk
Log Message:
tests/make: improve explanations in test for 'empty' function
To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 src/usr.bin/make/unit-tests/cond-func-empty.exp
cvs rdiff -u -r1.17 -r1.18 src/usr.bin/make/unit-tests/cond-func-empty.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/cond-func-empty.exp
diff -u src/usr.bin/make/unit-tests/cond-func-empty.exp:1.4 src/usr.bin/make/unit-tests/cond-func-empty.exp:1.5
--- src/usr.bin/make/unit-tests/cond-func-empty.exp:1.4 Sat Dec 11 09:53:53 2021
+++ src/usr.bin/make/unit-tests/cond-func-empty.exp Sat Mar 4 21:15:30 2023
@@ -1,5 +1,5 @@
-make: "cond-func-empty.mk" line 149: Unclosed variable "WORD"
-make: "cond-func-empty.mk" line 149: Malformed conditional (empty(WORD)
+make: "cond-func-empty.mk" line 153: Unclosed variable "WORD"
+make: "cond-func-empty.mk" line 153: Malformed conditional (empty(WORD)
make: Fatal errors encountered -- cannot continue
make: stopped in unit-tests
exit status 1
Index: src/usr.bin/make/unit-tests/cond-func-empty.mk
diff -u src/usr.bin/make/unit-tests/cond-func-empty.mk:1.17 src/usr.bin/make/unit-tests/cond-func-empty.mk:1.18
--- src/usr.bin/make/unit-tests/cond-func-empty.mk:1.17 Tue Dec 28 22:13:56 2021
+++ src/usr.bin/make/unit-tests/cond-func-empty.mk Sat Mar 4 21:15:30 2023
@@ -1,4 +1,4 @@
-# $NetBSD: cond-func-empty.mk,v 1.17 2021/12/28 22:13:56 rillig Exp $
+# $NetBSD: cond-func-empty.mk,v 1.18 2023/03/04 21:15:30 rillig Exp $
#
# Tests for the empty() function in .if conditions, which tests a variable
# expression for emptiness.
@@ -24,11 +24,13 @@ WORD= word
. error
.endif
-# The :S modifier replaces the empty value with an actual word. The
-# expression is now no longer empty, but it is still based on an undefined
-# variable (DEF_UNDEF). There are a few variable modifiers that turn an
-# undefined expression into a defined expression, among them :U and :D, but
-# not :S.
+# The :S modifier replaces the empty value with an actual word. After
+# applying the :S modifier to the expression, it value is 'empty', so it is
+# no longer empty, but it is still based on an undefined variable. There are
+# a few modifiers that turn an undefined expression into a defined expression,
+# among them :U and :D, but not :S. Therefore, at the end of evaluating the
+# expression, the expression is still undefined, so its final value becomes an
+# empty string.
#
# XXX: This is hard to explain to someone who doesn't know these
# implementation details.
@@ -45,15 +47,17 @@ WORD= word
. error
.endif
-# And now to the surprising part. Applying the following :S modifier to the
-# undefined expression makes it non-empty, but the expression is still in
-# state DEF_UNDEF. The :U modifier that follows only looks at the state
-# DEF_UNDEF to decide whether the variable is defined or not. This kind of
-# makes sense since the :U modifier tests the _variable_, not the
+# When an expression is based on an undefined variable, its modifiers interact
+# in sometimes surprising ways. Applying the :S modifier to the undefined
+# expression makes its value non-empty, but doesn't change that the expression
+# is based on an undefined variable. The :U modifier that follows only looks
+# at the definedness state to decide whether the variable is defined or not.
+# This kind of makes sense since the :U modifier tests the _variable_, not the
# _expression_.
#
-# But since the variable was undefined to begin with, the fallback value from
-# the :U modifier is used in this expression.
+# Since the variable was undefined to begin with, the fallback value from the
+# :U modifier is used in this expression, instead of keeping the 'value' from
+# the :S modifier.
#
.if ${UNDEF:S,^$,value,W:Ufallback} != "fallback"
. error
@@ -90,8 +94,8 @@ WORD= word
# neither leading nor trailing spaces are trimmed in the argument of the
# function. If the spaces were trimmed, the variable name would be "" and
# that variable is indeed undefined. Since CondParser_FuncCallEmpty calls
-# Var_Parse without VARE_UNDEFERR, the value of the undefined variable is
-# returned as an empty string.
+# Var_Parse without VARE_UNDEFERR, the value of the undefined variable ""
+# would be returned as an empty string.
${:U }= space
.if empty( )
. error
@@ -120,9 +124,9 @@ ${:U }= space
. error
.endif
-# Ensure that variable expressions that appear as part of the argument are
-# properly parsed. Typical use cases for this are .for loops, which are
-# expanded to exactly these ${:U} expressions.
+# Ensure that variable expressions that appear as part of the function call
+# argument are properly parsed. Typical use cases for this are .for loops,
+# which are expanded to exactly these ${:U} expressions.
#
# If everything goes well, the argument expands to "WORD", and that variable
# is defined at the beginning of this file. The surrounding 'W' and 'D'
@@ -159,10 +163,9 @@ ${:U WORD }= variable name with spaces
# Since at least 1993, the manual page claimed that irrelevant parts of
# conditions were not evaluated, but that was wrong for a long time. The
# expressions in irrelevant parts of the condition were actually evaluated,
-# they just allowed undefined variables to be used in the conditions, and the
-# result of evaluating them was not used further. These unnecessary
-# evaluations were fixed in several commits, starting with var.c 1.226 from
-# 2020-07-02.
+# they just allowed undefined variables to be used in the conditions. These
+# unnecessary evaluations were fixed in several commits, starting with var.c
+# 1.226 from 2020-07-02.
#
# In this example, the variable "VARNAME2" is not defined, so evaluation of
# the condition should have stopped at this point, and the rest of the
