A SET_IF_NOT_NULL() macro for optional return values

The SET_IF_NOT_NULL() macro avoids a fair amount of tedious boilerplate,
checking pointer parameters to see if they're non-NULL and updating
them if they are.  The macro was already in the dns_zone unit, and this
commit moves it to the <isc/util.h> header.

I have included a Coccinelle semantic patch to use SET_IF_NOT_NULL()
where appropriate. The patch needs an #include in `openssl_shim.c`
in order to work.

cocci/set_if_not_null.spatch

@@ -0,0 +1,14 @@
+@@
+type T;
+identifier fun;
+identifier arg;
+expression val;
+@@
+	fun(..., T *arg, ...) {
+		...
+-		if (arg != NULL) {
+-				*arg = val;
+-		}
++		SET_IF_NOT_NULL(arg, val);
+		...
+	}

lib/dns/openssl_shim.c

@@ -13,6 +13,8 @@
 
 #include "openssl_shim.h"
 
+#include <isc/util.h>
+
 #if !HAVE_RSA_SET0_KEY && OPENSSL_VERSION_NUMBER < 0x30000000L
 /* From OpenSSL 1.1.0 */
 int

lib/dns/zone.c

@@ -125,7 +125,7 @@
  */
 #define RANGE(a, min, max) (((a) < (min)) ? (min) : ((a) < (max) ? (a) : (max)))
 
-#define NSEC3REMOVE(x) (((x)&DNS_NSEC3FLAG_REMOVE) != 0)
+#define NSEC3REMOVE(x) (((x) & DNS_NSEC3FLAG_REMOVE) != 0)
 
 /*%
  * Key flags
@@ -5474,11 +5474,6 @@ invalidate_rdataset:
 	return (result);
 }
 
-#define SET_IF_NOT_NULL(obj, val) \
-	if (obj != NULL) {        \
-		*obj = val;       \
-	}
-
 #define SET_SOA_VALUES(soattl_v, serial_v, refresh_v, retry_v, expire_v, \
 		       minimum_v)                                        \
 	{                                                                \

lib/isc/histo.c

@@ -27,16 +27,6 @@
 #include <isc/mem.h>
 #include <isc/tid.h>
 
-/*
- * XXXFANF this should probably be in <isc/util.h> too
- */
-#define OUTARG(ptr, val)                \
-	({                              \
-		if ((ptr) != NULL) {    \
-			*(ptr) = (val); \
-		}                       \
-	})
-
 #define HISTO_MAGIC	    ISC_MAGIC('H', 's', 't', 'o')
 #define HISTO_VALID(p)	    ISC_MAGIC_VALID(p, HISTO_MAGIC)
 #define HISTOMULTI_MAGIC    ISC_MAGIC('H', 'g', 'M', 't')
@@ -327,9 +317,9 @@ isc_histo_get(const isc_histo_t *hg, uint key, uint64_t *minp, uint64_t *maxp,
 	REQUIRE(HISTO_VALID(hg));
 
 	if (key < BUCKETS(hg)) {
-		OUTARG(minp, key_to_minval(hg, key));
-		OUTARG(maxp, key_to_maxval(hg, key));
-		OUTARG(countp, get_key_count(hg, key));
+		SET_IF_NOT_NULL(minp, key_to_minval(hg, key));
+		SET_IF_NOT_NULL(maxp, key_to_maxval(hg, key));
+		SET_IF_NOT_NULL(countp, get_key_count(hg, key));
 		return (ISC_R_SUCCESS);
 	} else {
 		return (ISC_R_RANGE);
@@ -465,9 +455,9 @@ isc_histo_moments(const isc_histo_t *hg, double *pm0, double *pm1,
 		sigma += count * delta * (value - mean);
 	}
 
-	OUTARG(pm0, pop);
-	OUTARG(pm1, mean);
-	OUTARG(pm2, (pop > 0) ? sqrt(sigma / pop) : 0.0);
+	SET_IF_NOT_NULL(pm0, pop);
+	SET_IF_NOT_NULL(pm1, mean);
+	SET_IF_NOT_NULL(pm2, (pop > 0) ? sqrt(sigma / pop) : 0.0);
 }
 
 /*

lib/isc/include/isc/util.h

@@ -96,6 +96,14 @@
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
 
+/*
+ * Optional return values, or out-arguments
+ */
+#define SET_IF_NOT_NULL(obj, val) \
+	if ((obj) != NULL) {      \
+		*(obj) = (val);   \
+	}
+
 /*%
  * Get the allocation size for a struct with a flexible array member
  * containing `count` elements. The struct is identified by a pointer,