Add support for suffixes with multiple dots

input.c

@@ -723,20 +723,23 @@ target_type(char *s)
 			return s_type[ret];
 
 	// Check for an inference rule
-	ret = T_NORMAL;
-	sfx = suffix(s);
-	if (is_suffix(sfx)) {
-		if (s == sfx) {	// Single suffix rule
-			ret = T_INFERENCE | T_NOPREREQ | T_COMMAND;
-		} else {
-			// Suffix is valid, check that prefix is too
-			*sfx = '\0';
-			if (is_suffix(s))
-				ret = T_INFERENCE | T_NOPREREQ | T_COMMAND;
-			*sfx = '.';
-		}
+	for (sfx = s; (sfx = strchr(sfx + 1, '.'));) {
+		if (!is_suffix(sfx))
+			continue;
+
+		// Suffix is valid, check that prefix is too
+		*sfx = '\0';
+		ret = is_suffix(s);
+		*sfx = '.';
+
+		if (ret)
+			return T_INFERENCE | T_NOPREREQ | T_COMMAND;
 	}
-	return ret;
+
+	if (is_suffix(s)) // Single suffix rule
+		return T_INFERENCE | T_NOPREREQ | T_COMMAND;
+
+	return T_NORMAL;
 }
 
 #if ENABLE_FEATURE_MAKE_EXTENSIONS

rules.c

@@ -10,7 +10,7 @@
 char *
 suffix(const char *name)
 {
-	char *p = strrchr(name, '.');
+	char *p = strchr(name, '.');
 	return p ? p : (char *)name + strlen(name);
 }
 

testsuite/make.tests

@@ -100,6 +100,19 @@ x.p:
 '
 cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
 
+# Suffixes with multiple dots are supported
+mkdir make.tempdir && cd make.tempdir || exit 1
+testing "Support multi-dot suffixes" \
+	"make -f -" "touch x.c.c\ncat x.c.c >x.o.o\n" "" '
+.SUFFIXES: .c.c .o.o
+x.o.o:
+x.c.c:
+	touch $@
+.c.c.o.o:
+	cat $< >$@
+'
+cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
+
 # Austin Group defect report 875 clarifies certain aspects of the
 # behaviour of inference rules.  Study of this resulted in a number
 # of changes to pdpmake, though this test passed anyway.