make: phony targets and double colon rules

Commit 770bad1fe (make: disallow inference rules for phony targets)
added the GNU/BSD make feature that inference rules aren't used
for phony targets.

Normally a double-colon rule without associated commands causes
an inference rule search.  If the target of the double-colon rule
was phony no search was carried out and the rule failed.  As a
result of this perl failed to build (on Linux, I didn't try on
Windows).

When a double-colon rule has no commands and a phony target the
prerequisites should be built and the rule should succeed.

Adds 32 bytes.

(pdpmake GitHub issue #70)

1 files changed, 12 insertions, 7 deletions

diff --git a/miscutils/make.c b/miscutils/make.c
index 333f8bf12..ceac1d91d 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -2838,11 +2838,13 @@ make(struct name *np, int level)
                 }
         } else {
                 // If any double-colon rule has no commands we need
-                // an inference rule (but, as an extension, not for phony targets)
+                // an inference rule.
                 for (rp = np->n_rule; rp; rp = rp->r_next) {
                         if (!rp->r_cmd) {
-                                if (posix || !(np->n_flag & N_PHONY))
-                                        impdep = dyndep(np, &infrule, &tsuff);
+                                // Phony targets don't need an inference rule.
+                                if (!posix && (np->n_flag & N_PHONY))
+                                        continue;
+                                impdep = dyndep(np, &infrule, &tsuff);
                                 if (!impdep) {
                                         if (doinclude)
                                                 return 1;
@@ -2868,11 +2870,14 @@ make(struct name *np, int level)
                 // Each double-colon rule is handled separately.
                 if ((np->n_flag & N_DOUBLE)) {
                         // If the rule has no commands use the inference rule.
+                        // Unless there isn't one, as allowed for phony targets.
                         if (!rp->r_cmd) {
-                                locdep = impdep;
-                                infrule.r_dep->d_next = rp->r_dep;
-                                rp->r_dep = infrule.r_dep;
-                                rp->r_cmd = infrule.r_cmd;
+                                if (impdep) {
+                                        locdep = impdep;
+                                        infrule.r_dep->d_next = rp->r_dep;
+                                        rp->r_dep = infrule.r_dep;
+                                        rp->r_cmd = infrule.r_cmd;
+                                }
                         }
                         // A rule with no prerequisities is executed unconditionally.
                         if (!rp->r_dep)