make: support $+ and $^ as POSIX 202X features

Austin Group defect reports 514 and 1520 have both been accepted.
Together these introduce the internal macros $+ and $^:

- $+ lists all prerequisites, with duplicates retained;

- $^ lists all prerequisites, with duplicates removed.

$^ had already been implemented as a non-POSIX extension, it now
becomes a POSIX 202X extension.  $+ has been added as a POSIX
202X extension.

Neither of the above defect reports mentions how $? should handle
duplicate prerequisites.  In POSIX mode duplicates are retained.
Removal of duplicates is implemented as a non-POSIX extension to
match existing practice in other versions of make.

2 files changed, 31 insertions, 14 deletions

diff --git a/miscutils/make.c b/miscutils/make.c
index 21d0ede51..8e3778461 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -1927,15 +1927,17 @@ touch(struct name *np)
 
 static int
 make1(struct name *np, struct cmd *cp, char *oodate, char *allsrc,
-                struct name *implicit)
+                char *dedup, struct name *implicit)
 {
         int estat = 0;  // 0 exit status is success
         char *name, *member = NULL, *base;
 
         name = splitlib(np->n_name, &member);
         setmacro("?", oodate, 0 | M_VALID);
-        if (!posix)
-                setmacro("^", allsrc, 0 | M_VALID);
+        if (!posix) {
+                setmacro("+", allsrc, 0 | M_VALID);
+                setmacro("^", dedup, 0 | M_VALID);
+        }
         setmacro("%", member, 0 | M_VALID);
         setmacro("@", name, 0 | M_VALID);
         if (implicit) {
@@ -1993,6 +1995,7 @@ make(struct name *np, int level)
         struct cmd *sc_cmd = NULL;      // commands for single-colon rule
         char *oodate = NULL;
         char *allsrc = NULL;
+        char *dedup = NULL;
         struct timespec dtim = {1, 0};
         bool didsomething = 0;
         bool estat = 0; // 0 exit status is success
@@ -2080,17 +2083,17 @@ make(struct name *np, int level)
                         // Make prerequisite
                         estat |= make(dp->d_name, level + 1);
 
-                        // Make strings of out-of-date prerequisites (for $?)
-                        // and all prerequisites (for $^).  But not if we were
-                        // invoked with -q.
-                        if (!quest
-                                        // Skip duplicate entries.
-                                        && (posix || !(dp->d_name->n_flag & N_MARK))
-                        ) {
+                        // Make strings of out-of-date prerequisites (for $?),
+                        // all prerequisites (for $+) and deduplicated prerequisites
+                        // (for $^).  But not if we were invoked with -q.
+                        if (!quest) {
                                 if (timespec_le(&np->n_tim, &dp->d_name->n_tim)) {
-                                        oodate = xappendword(oodate, dp->d_name->n_name);
+                                        if (posix || !(dp->d_name->n_flag & N_MARK))
+                                                oodate = xappendword(oodate, dp->d_name->n_name);
                                 }
                                 allsrc = xappendword(allsrc, dp->d_name->n_name);
+                                if (!(dp->d_name->n_flag & N_MARK))
+                                        dedup = xappendword(dedup, dp->d_name->n_name);
                                 dp->d_name->n_flag |= N_MARK;
                         }
                         dtim = *timespec_max(&dtim, &dp->d_name->n_tim);
@@ -2099,7 +2102,7 @@ make(struct name *np, int level)
                         if (!quest && ((np->n_flag & N_PHONY) ||
                                                         timespec_le(&np->n_tim, &dtim))) {
                                 if (estat == 0) {
-                                        estat = make1(np, rp->r_cmd, oodate, allsrc, locdep);
+                                        estat = make1(np, rp->r_cmd, oodate, allsrc, dedup, locdep);
                                         dtim = (struct timespec){1, 0};
                                         didsomething = 1;
                                 }
@@ -2107,7 +2110,8 @@ make(struct name *np, int level)
                                 oodate = NULL;
                         }
                         free(allsrc);
-                        allsrc = NULL;
+                        free(dedup);
+                        allsrc = dedup = NULL;
                         if (locdep) {
                                 rp->r_dep = rp->r_dep->d_next;
                                 rp->r_cmd = NULL;
@@ -2132,7 +2136,7 @@ make(struct name *np, int level)
                                 if (!doinclude)
                                         bb_error_msg("nothing to be done for %s", np->n_name);
                         } else {
-                                estat = make1(np, sc_cmd, oodate, allsrc, impdep);
+                                estat = make1(np, sc_cmd, oodate, allsrc, dedup, impdep);
                                 clock_gettime(CLOCK_REALTIME, &np->n_tim);
                         }
                 } else if (!doinclude) {
@@ -2145,6 +2149,7 @@ make(struct name *np, int level)
                 printf("%s: '%s' is up to date\n", applet_name, np->n_name);
         }
         free(allsrc);
+        free(dedup);
         return estat;
 }
 
diff --git a/testsuite/make.tests b/testsuite/make.tests
index 3d0d14dd0..67617f8a2 100755
--- a/testsuite/make.tests
+++ b/testsuite/make.tests
@@ -255,6 +255,18 @@ mk:
 -include mk
 '
 
+# $^ skips duplicate prerequisites, $+ doesn't
+mkdir make.tempdir && cd make.tempdir || exit 1
+touch file1 file2 file3
+testing "make skip duplicate entries in \$^ but not \$+" \
+        "make -f -" \
+        "file1 file2 file3\nfile1 file2 file2 file3 file3\n" "" '
+target: file1 file2 file2 file3 file3
+        @echo $^
+        @echo $+
+'
+cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
+
 # Nested macro expansion is allowed.  This should be compatible
 # with other implementations.
 testing "make nested macro expansion" \