I have added these macros to c.h:

#define HIGHBIT                 (0x80)
        #define IS_HIGHBIT_SET(ch)      ((unsigned char)(ch) & HIGHBIT)

and removed CSIGNBIT and mapped it uses to HIGHBIT.  I have also added
uses for IS_HIGHBIT_SET where appropriate.  This change is
purely for code clarity.

src/backend/access/common/heaptuple.c

@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/common/heaptuple.c,v 1.104 2005/11/22 18:17:05 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/common/heaptuple.c,v 1.105 2005/12/25 02:14:17 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -111,7 +111,7 @@ heap_fill_tuple(TupleDesc tupleDesc,
 	if (bit != NULL)
 	{
 		bitP = &bit[-1];
-		bitmask = CSIGNBIT;
+		bitmask = HIGHBIT;
 	}
 	else
 	{
@@ -128,7 +128,7 @@ heap_fill_tuple(TupleDesc tupleDesc,
 
 		if (bit != NULL)
 		{
-			if (bitmask != CSIGNBIT)
+			if (bitmask != HIGHBIT)
 				bitmask <<= 1;
 			else
 			{
@@ -210,7 +210,7 @@ DataFill(char *data,
 	if (bit != NULL)
 	{
 		bitP = &bit[-1];
-		bitmask = CSIGNBIT;
+		bitmask = HIGHBIT;
 	}
 	else
 	{
@@ -227,7 +227,7 @@ DataFill(char *data,
 
 		if (bit != NULL)
 		{
-			if (bitmask != CSIGNBIT)
+			if (bitmask != HIGHBIT)
 				bitmask <<= 1;
 			else
 			{

src/backend/parser/scansup.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/scansup.c,v 1.30 2005/10/15 02:49:22 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/scansup.c,v 1.31 2005/12/25 02:14:17 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -149,7 +149,7 @@ downcase_truncate_identifier(const char *ident, int len, bool warn)
 
 		if (ch >= 'A' && ch <= 'Z')
 			ch += 'a' - 'A';
-		else if (ch >= 0x80 && isupper(ch))
+		else if (IS_HIGHBIT_SET(ch) && isupper(ch))
 			ch = tolower(ch);
 		result[i] = (char) ch;
 	}

src/backend/utils/adt/network.c

@@ -1,7 +1,7 @@
 /*
  *	PostgreSQL type definitions for the INET and CIDR types.
  *
- *	$PostgreSQL: pgsql/src/backend/utils/adt/network.c,v 1.56 2005/10/17 16:24:19 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/utils/adt/network.c,v 1.57 2005/12/25 02:14:17 momjian Exp $
  *
  *	Jon Postel RIP 16 Oct 1998
  */
@@ -904,16 +904,16 @@ bitncmp(void *l, void *r, int n)
 	rb = ((const u_char *) r)[b];
 	for (b = n % 8; b > 0; b--)
 	{
-		if ((lb & 0x80) != (rb & 0x80))
+		if (IS_HIGHBIT_SET(lb) != IS_HIGHBIT_SET(rb))
 		{
-			if (lb & 0x80)
-				return (1);
-			return (-1);
+			if (IS_HIGHBIT_SET(lb))
+				return 1;
+			return -1;
 		}
 		lb <<= 1;
 		rb <<= 1;
 	}
-	return (0);
+	return 0;
 }
 
 static bool

src/backend/utils/adt/varbit.c

@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/varbit.c,v 1.47 2005/10/15 02:49:30 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/varbit.c,v 1.48 2005/12/25 02:14:17 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -120,7 +120,7 @@ bit_in(PG_FUNCTION_ARGS)
 	{
 		/* Parse the bit representation of the string */
 		/* We know it fits, as bitlen was compared to atttypmod */
-		x = BITHIGH;
+		x = HIGHBIT;
 		for (; *sp; sp++)
 		{
 			if (*sp == '1')
@@ -134,7 +134,7 @@ bit_in(PG_FUNCTION_ARGS)
 			x >>= 1;
 			if (x == 0)
 			{
-				x = BITHIGH;
+				x = HIGHBIT;
 				r++;
 			}
 		}
@@ -401,7 +401,7 @@ varbit_in(PG_FUNCTION_ARGS)
 	{
 		/* Parse the bit representation of the string */
 		/* We know it fits, as bitlen was compared to atttypmod */
-		x = BITHIGH;
+		x = HIGHBIT;
 		for (; *sp; sp++)
 		{
 			if (*sp == '1')
@@ -415,7 +415,7 @@ varbit_in(PG_FUNCTION_ARGS)
 			x >>= 1;
 			if (x == 0)
 			{
-				x = BITHIGH;
+				x = HIGHBIT;
 				r++;
 			}
 		}
@@ -477,14 +477,14 @@ varbit_out(PG_FUNCTION_ARGS)
 		x = *sp;
 		for (k = 0; k < BITS_PER_BYTE; k++)
 		{
-			*r++ = (x & BITHIGH) ? '1' : '0';
+			*r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
 			x <<= 1;
 		}
 	}
 	x = *sp;
 	for (k = i; k < len; k++)
 	{
-		*r++ = (x & BITHIGH) ? '1' : '0';
+		*r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
 		x <<= 1;
 	}
 	*r = '\0';

src/backend/utils/mb/conv.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mb/conv.c,v 1.56 2005/10/29 00:31:52 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mb/conv.c,v 1.57 2005/12/25 02:14:17 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -413,7 +413,7 @@ LocalToUtf(unsigned char *iso, unsigned char *utf,
 
 	for (; len > 0 && *iso; len -= l)
 	{
-		if (*iso < 0x80)
+		if (!IS_HIGHBIT_SET(*iso))
 		{
 			*utf++ = *iso++;
 			l = 1;

src/backend/utils/mb/conversion_procs/euc_cn_and_mic/euc_cn_and_mic.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_cn_and_mic/euc_cn_and_mic.c,v 1.10 2005/09/24 17:53:18 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_cn_and_mic/euc_cn_and_mic.c,v 1.11 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -77,7 +77,7 @@ euc_cn2mic(unsigned char *euc, unsigned char *p, int len)
 
 	while (len >= 0 && (c1 = *euc++))
 	{
-		if (c1 & 0x80)
+		if (IS_HIGHBIT_SET(c1))
 		{
 			len -= 2;
 			*p++ = LC_GB2312_80;

src/backend/utils/mb/conversion_procs/euc_kr_and_mic/euc_kr_and_mic.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_kr_and_mic/euc_kr_and_mic.c,v 1.10 2005/09/24 17:53:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_kr_and_mic/euc_kr_and_mic.c,v 1.11 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -77,7 +77,7 @@ euc_kr2mic(unsigned char *euc, unsigned char *p, int len)
 
 	while (len >= 0 && (c1 = *euc++))
 	{
-		if (c1 & 0x80)
+		if (IS_HIGHBIT_SET(c1))
 		{
 			len -= 2;
 			*p++ = LC_KS5601;

src/backend/utils/mb/conversion_procs/euc_tw_and_big5/euc_tw_and_big5.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_tw_and_big5/euc_tw_and_big5.c,v 1.10 2005/09/24 17:53:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/euc_tw_and_big5/euc_tw_and_big5.c,v 1.11 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -177,7 +177,7 @@ euc_tw2mic(unsigned char *euc, unsigned char *p, int len)
 			*p++ = *euc++;
 			*p++ = *euc++;
 		}
-		else if (c1 & 0x80)
+		else if (IS_HIGHBIT_SET(c1))
 		{						/* CNS11643-1 */
 			len -= 2;
 			*p++ = LC_CNS11643_1;

src/backend/utils/mb/conversion_procs/utf8_and_iso8859_1/utf8_and_iso8859_1.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/utf8_and_iso8859_1/utf8_and_iso8859_1.c,v 1.12 2005/09/24 17:53:24 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mb/conversion_procs/utf8_and_iso8859_1/utf8_and_iso8859_1.c,v 1.13 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,12 +46,12 @@ iso8859_1_to_utf8(PG_FUNCTION_ARGS)
 
 	while (len-- > 0 && (c = *src++))
 	{
-		if (c < 0x80)
+		if (!IS_HIGHBIT_SET(c))
 			*dest++ = c;
 		else
 		{
 			*dest++ = (c >> 6) | 0xc0;
-			*dest++ = (c & 0x003f) | 0x80;
+			*dest++ = (c & 0x003f) | HIGHBIT;
 		}
 	}
 	*dest = '\0';

src/backend/utils/mb/wchar.c

@@ -1,7 +1,7 @@
 /*
  * conversion functions between pg_wchar and multibyte streams.
  * Tatsuo Ishii
- * $PostgreSQL: pgsql/src/backend/utils/mb/wchar.c,v 1.50 2005/12/24 17:19:40 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/mb/wchar.c,v 1.51 2005/12/25 02:14:18 momjian Exp $
  *
  * WIN1250 client encoding updated by Pavel Behal
  *
@@ -79,7 +79,7 @@ static int	pg_euc2wchar_with_len
 			*to |= *from++;
 			len -= 3;
 		}
-		else if ((*from & 0x80) && len >= 2)	/* JIS X 0208 KANJI */
+		else if (IS_HIGHBIT_SET(*from) && len >= 2)	/* JIS X 0208 KANJI */
 		{
 			*to = *from++ << 8;
 			*to |= *from++;
@@ -106,7 +106,7 @@ pg_euc_mblen(const unsigned char *s)
 		len = 2;
 	else if (*s == SS3)
 		len = 3;
-	else if (*s & 0x80)
+	else if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -122,7 +122,7 @@ pg_euc_dsplen(const unsigned char *s)
 		len = 2;
 	else if (*s == SS3)
 		len = 2;
-	else if (*s & 0x80)
+	else if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -153,7 +153,7 @@ pg_eucjp_dsplen(const unsigned char *s)
 		len = 1;
 	else if (*s == SS3)
 		len = 2;
-	else if (*s & 0x80)
+	else if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -206,7 +206,7 @@ static int	pg_euccn2wchar_with_len
 			*to |= *from++;
 			len -= 3;
 		}
-		else if ((*from & 0x80) && len >= 2)	/* code set 1 */
+		else if (IS_HIGHBIT_SET(*from) && len >= 2)	/* code set 1 */
 		{
 			*to = *from++ << 8;
 			*to |= *from++;
@@ -229,7 +229,7 @@ pg_euccn_mblen(const unsigned char *s)
 {
 	int			len;
 
-	if (*s & 0x80)
+	if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -241,7 +241,7 @@ pg_euccn_dsplen(const unsigned char *s)
 {
 	int			len;
 
-	if (*s & 0x80)
+	if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -274,7 +274,7 @@ static int	pg_euctw2wchar_with_len
 			*to |= *from++;
 			len -= 3;
 		}
-		else if ((*from & 0x80) && len >= 2)	/* code set 2 */
+		else if (IS_HIGHBIT_SET(*from) && len >= 2)	/* code set 2 */
 		{
 			*to = *from++ << 8;
 			*to |= *from++;
@@ -301,7 +301,7 @@ pg_euctw_mblen(const unsigned char *s)
 		len = 4;
 	else if (*s == SS3)
 		len = 3;
-	else if (*s & 0x80)
+	else if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -317,7 +317,7 @@ pg_euctw_dsplen(const unsigned char *s)
 		len = 2;
 	else if (*s == SS3)
 		len = 2;
-	else if (*s & 0x80)
+	else if (IS_HIGHBIT_SET(*s))
 		len = 2;
 	else
 		len = 1;
@@ -361,7 +361,7 @@ pg_utf2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
 
 	while (len > 0 && *from)
 	{
-		if ((*from & 0x80) == 0)
+		if (!IS_HIGHBIT_SET(*from))
 		{
 			*to = *from++;
 			len--;
@@ -866,7 +866,7 @@ pg_verifymbstr(const char *mbstr, int len, bool noError)
 				 * we expect that every multibyte char consists of bytes
 				 * having the 8th bit set
 				 */
-				if (i >= len || (mbstr[i] & 0x80) == 0)
+				if (i >= len || !IS_HIGHBIT_SET(mbstr[i]))
 				{
 					char		buf[8 * 2 + 1];
 					char	   *p = buf;

src/include/c.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/c.h,v 1.192 2005/12/06 02:29:03 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/c.h,v 1.193 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -704,7 +704,8 @@ typedef NameData *Name;
  */
 
 /* msb for char */
-#define CSIGNBIT (0x80)
+#define HIGHBIT					(0x80)
+#define IS_HIGHBIT_SET(ch)		((unsigned char)(ch) & HIGHBIT)
 
 #define STATUS_OK				(0)
 #define STATUS_ERROR			(-1)

src/include/utils/varbit.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/varbit.h,v 1.21 2004/12/31 22:03:46 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/utils/varbit.h,v 1.22 2005/12/25 02:14:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,7 +58,6 @@ typedef struct
 #define VARBITEND(PTR)		(((bits8 *) (PTR)) + VARSIZE(PTR))
 /* Mask that will cover exactly one byte, i.e. BITS_PER_BYTE bits */
 #define BITMASK 0xFF
-#define BITHIGH 0x80
 
 
 extern Datum bit_in(PG_FUNCTION_ARGS);

src/port/pgstrcasecmp.c

@@ -16,7 +16,7 @@
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/port/pgstrcasecmp.c,v 1.5 2004/12/31 22:03:53 pgsql Exp $
+ * $PostgreSQL: pgsql/src/port/pgstrcasecmp.c,v 1.6 2005/12/25 02:14:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -40,12 +40,12 @@ pg_strcasecmp(const char *s1, const char *s2)
 		{
 			if (ch1 >= 'A' && ch1 <= 'Z')
 				ch1 += 'a' - 'A';
-			else if (ch1 >= 0x80 && isupper(ch1))
+			else if (IS_HIGHBIT_SET(ch1) && isupper(ch1))
 				ch1 = tolower(ch1);
 
 			if (ch2 >= 'A' && ch2 <= 'Z')
 				ch2 += 'a' - 'A';
-			else if (ch2 >= 0x80 && isupper(ch2))
+			else if (IS_HIGHBIT_SET(ch2) && isupper(ch2))
 				ch2 = tolower(ch2);
 
 			if (ch1 != ch2)
@@ -73,12 +73,12 @@ pg_strncasecmp(const char *s1, const char *s2, size_t n)
 		{
 			if (ch1 >= 'A' && ch1 <= 'Z')
 				ch1 += 'a' - 'A';
-			else if (ch1 >= 0x80 && isupper(ch1))
+			else if (IS_HIGHBIT_SET(ch1) && isupper(ch1))
 				ch1 = tolower(ch1);
 
 			if (ch2 >= 'A' && ch2 <= 'Z')
 				ch2 += 'a' - 'A';
-			else if (ch2 >= 0x80 && isupper(ch2))
+			else if (IS_HIGHBIT_SET(ch2) && isupper(ch2))
 				ch2 = tolower(ch2);
 
 			if (ch1 != ch2)
@@ -102,7 +102,7 @@ pg_toupper(unsigned char ch)
 {
 	if (ch >= 'a' && ch <= 'z')
 		ch += 'A' - 'a';
-	else if (ch >= 0x80 && islower(ch))
+	else if (IS_HIGHBIT_SET(ch) && islower(ch))
 		ch = toupper(ch);
 	return ch;
 }
@@ -119,7 +119,7 @@ pg_tolower(unsigned char ch)
 {
 	if (ch >= 'A' && ch <= 'Z')
 		ch += 'a' - 'A';
-	else if (ch >= 0x80 && isupper(ch))
+	else if (IS_HIGHBIT_SET(ch) && isupper(ch))
 		ch = tolower(ch);
 	return ch;
 }