Add .unexport - the exact opposite of .export

and .unexport-env which unexport's all previously .export'd globals
as well as clearing environ[].
Allow's sys.mk near total controll.

Reviewed by: apb

usr.bin/make/make.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: make.1,v 1.164 2009/10/15 02:27:44 joerg Exp $
+.\"	$NetBSD: make.1,v 1.165 2009/11/19 00:30:24 sjg Exp $
 .\"
 .\" Copyright (c) 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"	from: @(#)make.1	8.4 (Berkeley) 3/19/94
 .\"
-.Dd October 1, 2009
+.Dd November 15, 2009
 .Dt MAKE 1
 .Os
 .Sh NAME
@@ -1274,17 +1274,53 @@ Conditional expressions are also preceded by a single dot as the first
 character of a line.
 The possible conditionals are as follows:
 .Bl -tag -width Ds
-.It Ic .export Ar variable
+.It Ic .export Ar variable ...
 Export the specified global variable.
-If no variable is provided, all globals are exported
+If no variable list is provided, all globals are exported
 except for internal variables (those that start with
 .Ql \&. ) .
 This is not affected by the
 .Fl X
 flag, so should be used with caution.
+.Pp
 Appending a variable name to
 .Va .MAKE.EXPORTED
 is equivalent to exporting a variable.
+.It Ic .unexport Ar variable ...
+The opposite of
+.Ql .export .
+The specified global
+.Va variable 
+will be removed from 
+.Va .MAKE.EXPORTED .
+If no variable list is provided, all globals are unexported,
+and
+.Va .MAKE.EXPORTED 
+deleted.
+.It Ic .unexport-env
+Unexport all globals previously exported and
+clear the environment inherited from the parent.
+This operation will cause a memory leak of the original environment, 
+so should be used sparingly.  Testing for 
+.Va .MAKE.LEVEL
+being 0, would make sense.
+Also note that any variables which originated in the parent environment 
+should be explicitly preserved if desired.
+For example:
+.Bd -literal -offset indent
+.Li .if ${.MAKE.LEVEL} == 0
+PATH := ${PATH}
+.Li .unexport-env
+.Li .export PATH
+.Li .endif
+.Pp
+.Ed
+Would result in an environment containing only 
+.Ql Ev PATH ,
+which is the minimal useful environment.
+Actually
+.Ql Ev .MAKE.LEVEL 
+will also be pushed into the new environment.
 .It Ic .undef Ar variable
 Un-define the specified global variable.
 Only global variables may be un-defined.

usr.bin/make/nonints.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: nonints.h,v 1.56 2009/01/28 21:38:13 dsl Exp $	*/
+/*	$NetBSD: nonints.h,v 1.57 2009/11/19 00:30:24 sjg Exp $	*/
 
 /*-
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -193,3 +193,4 @@ void Var_End(void);
 void Var_Dump(GNode *);
 void Var_ExportVars(void);
 void Var_Export(char *, int);
+void Var_UnExport(char *);

usr.bin/make/parse.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: parse.c,v 1.159 2009/11/06 20:20:56 dsl Exp $	*/
+/*	$NetBSD: parse.c,v 1.160 2009/11/19 00:30:25 sjg Exp $	*/
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -69,14 +69,14 @@
  */
 
 #ifndef MAKE_NATIVE
-static char rcsid[] = "$NetBSD: parse.c,v 1.159 2009/11/06 20:20:56 dsl Exp $";
+static char rcsid[] = "$NetBSD: parse.c,v 1.160 2009/11/19 00:30:25 sjg Exp $";
 #else
 #include <sys/cdefs.h>
 #ifndef lint
 #if 0
 static char sccsid[] = "@(#)parse.c	8.3 (Berkeley) 3/19/94";
 #else
-__RCSID("$NetBSD: parse.c,v 1.159 2009/11/06 20:20:56 dsl Exp $");
+__RCSID("$NetBSD: parse.c,v 1.160 2009/11/19 00:30:25 sjg Exp $");
 #endif
 #endif /* not lint */
 #endif
@@ -2510,6 +2510,9 @@ Parse_File(const char *name, int fd)
 			continue;
 		    Var_Export(cp, 1);
 		    continue;
+		} else if (strncmp(cp, "unexport", 8) == 0) {
+		    Var_UnExport(cp);
+		    continue;
 		}
 	    }
 

usr.bin/make/unit-tests/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.24 2009/10/07 16:40:30 sjg Exp $
+# $NetBSD: Makefile,v 1.25 2009/11/19 00:30:25 sjg Exp $
 #
 # Unit tests for make(1)
 # The main targets are:
@@ -34,6 +34,8 @@ SUBFILES= \
 	posix \
 	qequals \
 	ternary \
+	unexport \
+	unexport-env \
 	varcmd
 
 all: ${SUBFILES}