Tweak a couple of macros in the regex code to suppress compiler warnings

from "clang".  The VERR changes make an assignment unconditional, which is
probably easier to read/understand anyway, and one can hardly argue that
it's worth shaving cycles off the case of reporting another error when
one has already been detected.  The INSIST change limits where that macro
can be used, but not in a way that creates a problem for any existing call.

src/backend/regex/regcomp.c

@@ -28,7 +28,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $PostgreSQL: pgsql/src/backend/regex/regcomp.c,v 1.48 2010/02/26 02:00:57 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/regex/regcomp.c,v 1.49 2010/08/02 02:29:39 tgl Exp $
  *
  */
 
@@ -232,13 +232,13 @@ struct vars
 #define EAT(t)	(SEE(t) && next(v))		/* if next is this, swallow it */
 #define VISERR(vv)	((vv)->err != 0)	/* have we seen an error yet? */
 #define ISERR() VISERR(v)
-#define VERR(vv,e)	((vv)->nexttype = EOS, ((vv)->err) ? (vv)->err :\
-							((vv)->err = (e)))
+#define VERR(vv,e)	((vv)->nexttype = EOS, \
+					 (vv)->err = ((vv)->err ? (vv)->err : (e)))
 #define ERR(e)	VERR(v, e)		/* record an error */
 #define NOERR() {if (ISERR()) return;}	/* if error seen, return */
 #define NOERRN()	{if (ISERR()) return NULL;} /* NOERR with retval */
 #define NOERRZ()	{if (ISERR()) return 0;}	/* NOERR with retval */
-#define INSIST(c, e)	((c) ? 0 : ERR(e))		/* if condition false, error */
+#define INSIST(c, e) do { if (!(c)) ERR(e); } while (0)	/* error if c false */
 #define NOTE(b) (v->re->re_info |= (b)) /* note visible condition */
 #define EMPTYARC(x, y)	newarc(v->nfa, EMPTY, 0, x, y)
 

src/backend/regex/regexec.c

@@ -27,7 +27,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $PostgreSQL: pgsql/src/backend/regex/regexec.c,v 1.28 2010/02/01 02:45:29 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/regex/regexec.c,v 1.29 2010/08/02 02:29:39 tgl Exp $
  *
  */
 
@@ -119,7 +119,7 @@ struct vars
 
 #define VISERR(vv)	((vv)->err != 0)	/* have we seen an error yet? */
 #define ISERR() VISERR(v)
-#define VERR(vv,e)	(((vv)->err) ? (vv)->err : ((vv)->err = (e)))
+#define VERR(vv,e)	((vv)->err = ((vv)->err ? (vv)->err : (e)))
 #define ERR(e)	VERR(v, e)		/* record an error */
 #define NOERR() {if (ISERR()) return v->err;}	/* if error seen, return it */
 #define OFF(p)	((p) - v->start)