[src/trunk]: src/usr.bin/make make(1): in lint mode, allow undefined variable...

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

details:   https://anonhg.NetBSD.org/src/rev/a7f6172a33c2
branches:  trunk
changeset: 944017:a7f6172a33c2
user:      rillig <rillig%NetBSD.org@localhost>
date:      Mon Sep 14 21:23:58 2020 +0000

description:
make(1): in lint mode, allow undefined variables in dependency lines

This is needed to get past the first few seconds in a src/build.sh run.

The nest obstacle is src/tools/Makefile.gnuhost:30, where the variable
MODULE is undefined even though that file says in line 3 that MODULE is
expected to be set.  It has been saying this since 2001, but since make
didn't have the corresponding check enabled, this didn't break the
build.

diffstat:

 usr.bin/make/parse.c                      |  40 +++++++++++++++++++++++++++---
 usr.bin/make/unit-tests/opt-debug-lint.mk |   7 ++++-
 2 files changed, 41 insertions(+), 6 deletions(-)

diffs (82 lines):

diff -r 3c0602ca18ea -r a7f6172a33c2 usr.bin/make/parse.c
--- a/usr.bin/make/parse.c      Mon Sep 14 20:43:44 2020 +0000
+++ b/usr.bin/make/parse.c      Mon Sep 14 21:23:58 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: parse.c,v 1.319 2020/09/14 19:59:47 rillig Exp $       */
+/*     $NetBSD: parse.c,v 1.320 2020/09/14 21:23:58 rillig Exp $       */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -131,7 +131,7 @@
 #include "pathnames.h"
 
 /*     "@(#)parse.c    8.3 (Berkeley) 3/19/94" */
-MAKE_RCSID("$NetBSD: parse.c,v 1.319 2020/09/14 19:59:47 rillig Exp $");
+MAKE_RCSID("$NetBSD: parse.c,v 1.320 2020/09/14 21:23:58 rillig Exp $");
 
 /* types and constants */
 
@@ -3067,10 +3067,40 @@
 
            /*
             * We now know it's a dependency line so it needs to have all
-            * variables expanded before being parsed. Tell the variable
-            * module to complain if some variable is undefined...
+            * variables expanded before being parsed.
+            *
+            * XXX: Ideally the dependency line would first be split into
+            * its left-hand side, dependency operator and right-hand side,
+            * and then each side would be expanded on its own.  This would
+            * allow for the left-hand side to allow only defined variables
+            * and to allow variables on the right-hand side to be undefined
+            * as well.
+            *
+            * Parsing the line first would also prevent that targets
+            * generated from variable expressions are interpreted as the
+            * dependency operator, such as in "target${:U:} middle: source",
+            * in which the middle is interpreted as a source, not a target.
             */
-           line = Var_Subst(line, VAR_CMD, VARE_UNDEFERR|VARE_WANTRES);
+           {
+               /* In lint mode, allow undefined variables to appear in
+                * dependency lines.
+                *
+                * Ideally, only the right-hand side would allow undefined
+                * variables since it is common to have no dependencies.
+                * Having undefined variables on the left-hand side is more
+                * unusual though.  Since both sides are expanded in a single
+                * pass, there is not much choice what to do here.
+                *
+                * In normal mode, it does not matter whether undefined
+                * variables are allowed or not since as of 2020-09-14,
+                * Var_Parse does not print any parse errors in such a case.
+                * It simply returns the special empty string var_Error,
+                * which cannot be detected in the result of Var_Subst. */
+               VarEvalFlags eflags = DEBUG(LINT)
+                                     ? VARE_WANTRES
+                                     : VARE_UNDEFERR|VARE_WANTRES;
+               line = Var_Subst(line, VAR_CMD, eflags);
+           }
 
            /*
             * Need a list for the target nodes
diff -r 3c0602ca18ea -r a7f6172a33c2 usr.bin/make/unit-tests/opt-debug-lint.mk
--- a/usr.bin/make/unit-tests/opt-debug-lint.mk Mon Sep 14 20:43:44 2020 +0000
+++ b/usr.bin/make/unit-tests/opt-debug-lint.mk Mon Sep 14 21:23:58 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: opt-debug-lint.mk,v 1.4 2020/09/14 07:13:29 rillig Exp $
+# $NetBSD: opt-debug-lint.mk,v 1.5 2020/09/14 21:23:58 rillig Exp $
 #
 # Tests for the -dL command line option, which runs additional checks
 # to catch common mistakes, such as unclosed variable expressions.
@@ -42,5 +42,10 @@
 .  error
 .endif
 
+# Since 2020-09-14, dependency lines may contain undefined variables.
+# Before, undefined variables were forbidden, but this distinction was not
+# observable from the outside of the function Var_Parse.
+${UNDEF}: ${UNDEF}
+
 all:
        @:;