Add POSIX -p flag to make(1).

This article [1] describes the -p flag for make(1):

	Write to standard output the complete set of macro definitions and
	target descriptions. The output format is unspecified.

We already support a similar flag (-d g1), but unlike -p, it still
executes commands. Our implementation just turns it into -d g1, but also
sets flag `printGraphOnly', which will cause make(1) to skip execution.

[1] http://www.opengroup.org/onlinepubs/009695399/utilities/make.html

Reviewed by:	imp
PR:		standards/99960

2 files changed, 19 insertions, 4 deletions

diff --git a/usr.bin/make/main.c b/usr.bin/make/main.c
index 7be2aa2..7569d42 100644
--- a/usr.bin/make/main.c
+++ b/usr.bin/make/main.c
@@ -133,6 +133,7 @@ int		jobLimit;	/* -j argument */
 Boolean		jobsRunning;	/* TRUE if the jobs might be running */
 Boolean		keepgoing;	/* -k flag */
 Boolean		noExecute;	/* -n flag */
+Boolean		printGraphOnly;	/* -p flag */
 Boolean		queryFlag;	/* -q flag */
 Boolean		touchFlag;	/* -t flag */
 Boolean		usePipes;	/* !-P flag */
@@ -150,7 +151,7 @@ static void
 usage(void)
 {
 	fprintf(stderr,
-	    "usage: make [-BPSXeiknqrstv] [-C directory] [-D variable]\n"
+	    "usage: make [-BPSXeiknpqrstv] [-C directory] [-D variable]\n"
 	    "\t[-d flags] [-E variable] [-f makefile] [-I directory]\n"
 	    "\t[-j max_jobs] [-m directory] [-V variable]\n"
 	    "\t[variable=value] [target ...]\n");
@@ -368,7 +369,7 @@ MainParseArgs(int argc, char **argv)
 rearg:
 	optind = 1;	/* since we're called more than once */
 	optreset = 1;
-#define OPTFLAGS "ABC:D:E:I:PSV:Xd:ef:ij:km:nqrstvx:"
+#define OPTFLAGS "ABC:D:E:I:PSV:Xd:ef:ij:km:npqrstvx:"
 	for (;;) {
 		if ((optind < argc) && strcmp(argv[optind], "--") == 0) {
 			found_dd = TRUE;
@@ -510,6 +511,10 @@ rearg:
 			noExecute = TRUE;
 			MFLAGS_append("-n", NULL);
 			break;
+		case 'p':
+			printGraphOnly = TRUE;
+			debug |= DEBUG_GRAPH1;
+			break;
 		case 'q':
 			queryFlag = TRUE;
 			/* Kind of nonsensical, wot? */
@@ -903,6 +908,7 @@ main(int argc, char **argv)
 	beSilent = FALSE;		/* Print commands as executed */
 	ignoreErrors = FALSE;		/* Pay attention to non-zero returns */
 	noExecute = FALSE;		/* Execute all commands */
+	printGraphOnly = FALSE;		/* Don't stop after printing graph */
 	keepgoing = FALSE;		/* Stop on error */
 	allPrecious = FALSE;		/* Remove targets when interrupted */
 	queryFlag = FALSE;		/* This is not just a check-run */
@@ -1242,7 +1248,7 @@ main(int argc, char **argv)
 		Targ_PrintGraph(1);
 
 	/* print the values of any variables requested by the user */
-	if (Lst_IsEmpty(&variables)) {
+	if (Lst_IsEmpty(&variables) && !printGraphOnly) {
 		/*
 		 * Since the user has not requested that any variables
 		 * be printed, we can build targets.
diff --git a/usr.bin/make/make.1 b/usr.bin/make/make.1
index 173aef3..44421e5 100644
--- a/usr.bin/make/make.1
+++ b/usr.bin/make/make.1
@@ -40,7 +40,7 @@
 .Nd maintain program dependencies
 .Sh SYNOPSIS
 .Nm
-.Op Fl ABPSXeiknqrstv
+.Op Fl ABPSXeiknpqrstv
 .Op Fl C Ar directory
 .Op Fl D Ar variable
 .Op Fl d Ar flags
@@ -249,6 +249,15 @@ instead of mixing the output of parallel jobs together.
 This option has no effect unless
 .Fl j
 is used too.
+.It Fl p
+Only print the input graph, not executing any commands.
+The output is the same as
+.Fl d Ar g1 .
+When combined with
+.Fl f Pa /dev/null ,
+only the builtin rules of
+.Nm
+are displayed.
 .It Fl q
 Do not execute any commands, but exit 0 if the specified targets are
 up-to-date and 1, otherwise.