[src/trunk]: src/usr.bin/make/unit-tests make(1): add more tests for the vari...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2ae410f86c51
branches:  trunk
changeset: 941934:2ae410f86c51
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sun Nov 01 19:49:28 2020 +0000

description:
make(1): add more tests for the variable modifier :M

Despite its popularity and usefulness, the variable modifier :M is
implemented so weirdly that it's not surprising people get confused
about make's parsing and escaping rules.

diffstat:

 usr.bin/make/unit-tests/varmod-match-escape.exp |   5 +++-
 usr.bin/make/unit-tests/varmod-match-escape.mk  |  26 ++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 2 deletions(-)

diffs (51 lines):

diff -r 33a726580b52 -r 2ae410f86c51 usr.bin/make/unit-tests/varmod-match-escape.exp
--- a/usr.bin/make/unit-tests/varmod-match-escape.exp   Sun Nov 01 19:47:46 2020 +0000
+++ b/usr.bin/make/unit-tests/varmod-match-escape.exp   Sun Nov 01 19:49:28 2020 +0000
@@ -55,4 +55,7 @@
 make: "varmod-match-escape.mk" line 42: warning: XXX: Oops
 Global:.MAKEFLAGS =  -r -k -d cv -d
 Global:.MAKEFLAGS =  -r -k -d cv -d 0
-exit status 0
+make: "varmod-match-escape.mk" line 67: Dollar followed by nothing
+make: Fatal errors encountered -- cannot continue
+make: stopped in unit-tests
+exit status 1
diff -r 33a726580b52 -r 2ae410f86c51 usr.bin/make/unit-tests/varmod-match-escape.mk
--- a/usr.bin/make/unit-tests/varmod-match-escape.mk    Sun Nov 01 19:47:46 2020 +0000
+++ b/usr.bin/make/unit-tests/varmod-match-escape.mk    Sun Nov 01 19:49:28 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: varmod-match-escape.mk,v 1.4 2020/11/01 19:25:23 rillig Exp $
+# $NetBSD: varmod-match-escape.mk,v 1.5 2020/11/01 19:49:28 rillig Exp $
 #
 # As of 2020-08-01, the :M and :N modifiers interpret backslashes differently,
 # depending on whether there was a variable expression somewhere before the
@@ -44,5 +44,29 @@
 
 .MAKEFLAGS: -d0
 
+# XXX: As of 2020-11-01, unlike all other variable modifiers, a '$' in the
+# :M and :N modifiers is written as '$$', not as '\$'.  This is confusing,
+# undocumented and hopefully not used in practice.
+.if ${:U\$:M$$} != "\$"
+.  error
+.endif
+
+# XXX: As of 2020-11-01, unlike all other variable modifiers, '\$' is not
+# parsed as an escaped '$'.  Instead, ApplyModifier_Match first scans for
+# the ':' at the end of the modifier, which results in the pattern '\$'.
+# No unescaping takes place since the pattern neither contained '\:' nor
+# '\{' nor '\}'.  But the text is expanded, and a lonely '$' at the end
+# is silently discarded.  The resulting expanded pattern is thus '\', that
+# is a single backslash.
+.if ${:U\$:M\$} != ""
+.  error
+.endif
+
+# In lint mode, the case of a lonely '$' is covered with an error message.
+.MAKEFLAGS: -dL
+.if ${:U\$:M\$} != ""
+.  error
+.endif
+
 all:
        @:;