make: disallow inference rules for phony targets

GNU make doesn't allow inference rules or the .DEFAULT target to
be used for phony targets.

POSIX is unclear on the matter but there doesn't seem to be an
explicit prohibition of inference rules or .DEFAULT.

Follow the GNU make behaviour as a non-POSIX extension.

Adds 48-80 bytes.

(pdpmake GitHub issue 56)

2 files changed, 22 insertions, 5 deletions

diff --git a/miscutils/make.c b/miscutils/make.c
index 1dfbd8c44..8c74d7113 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -2611,9 +2611,10 @@ make(struct name *np, int level)
 
         if (!(np->n_flag & N_DOUBLE)) {
                 // Find the commands needed for a single-colon rule, using
-                // an inference rule or .DEFAULT rule if necessary
+                // an inference rule or .DEFAULT rule if necessary (but,
+                // as an extension, not for phony targets)
                 sc_cmd = getcmd(np);
-                if (!sc_cmd) {
+                if (!sc_cmd && (posix || !(np->n_flag & N_PHONY))) {
                         impdep = dyndep(np, &imprule);
                         if (impdep) {
                                 sc_cmd = imprule.r_cmd;
@@ -2623,7 +2624,8 @@ make(struct name *np, int level)
 
                 // As a last resort check for a default rule
                 if (!(np->n_flag & N_TARGET) && np->n_tim.tv_sec == 0) {
-                        sc_cmd = getcmd(findname(".DEFAULT"));
+                        if (posix || !(np->n_flag & N_PHONY))
+                                sc_cmd = getcmd(findname(".DEFAULT"));
                         if (!sc_cmd) {
                                 if (doinclude)
                                         return 1;
@@ -2634,10 +2636,11 @@ make(struct name *np, int level)
         }
         else {
                 // If any double-colon rule has no commands we need
-                // an inference rule
+                // an inference rule (but, as an extension, not for phony targets)
                 for (rp = np->n_rule; rp; rp = rp->r_next) {
                         if (!rp->r_cmd) {
-                                impdep = dyndep(np, &imprule);
+                                if (posix || !(np->n_flag & N_PHONY))
+                                        impdep = dyndep(np, &imprule);
                                 if (!impdep) {
                                         if (doinclude)
                                                 return 1;
diff --git a/testsuite/make.tests b/testsuite/make.tests
index 5485233f6..c92c69340 100755
--- a/testsuite/make.tests
+++ b/testsuite/make.tests
@@ -738,4 +738,18 @@ file1:
 '
 cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
 
+# GNU make and BSD make don't allow the use of inference rules
+# for phony targets.  In POSIX mode the output is "phony.xyz\n".
+mkdir make.tempdir && cd make.tempdir || exit 1
+touch phony.xyz
+testing "make don't use inference rule for phony target" \
+        "make -f -" "make: nothing to be done for phony\n" "" '
+.PHONY: phony
+.SUFFIXES: .xyz
+.xyz:
+        @echo $<
+phony:
+'
+cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
+
 exit $FAILCOUNT