4 files changed, 45 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 05f53423..e685dd6f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,16 @@
 	of unexpected data.  Make the lint warning an unconditional
 	warning.
 
+	Unrelated:
+
+	* awk.h: Add explanatory comment on the flags related to
+	types and values.
+	* mpfr.c (mpg_force_number): If setting NUMBER, clear STRING also
+	when clearing MAYBE_NUM.
+	(set_PREC): Check STRCUR instead of STRING.
+	* node.c (r_force_number): If setting NUMBER, clear STRING also
+	when clearing MAYBE_NUM.
+
 2015-08-15         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* dfa.c (dfamust): Restore c90 compat by moving some
diff --git a/awk.h b/awk.h
index 1eb26880..c3a3cba7 100644
--- a/awk.h
+++ b/awk.h
@@ -404,6 +404,37 @@ typedef struct exp_node {
 #		define	MALLOC	0x0001       /* can be free'd */
 
 /* type = Node_val */
+	/*
+	 * STRING and NUMBER are mutually exclusive. They represent the
+	 * type of a value as assigned.
+	 *
+	 * STRCUR and NUMCUR are not mutually exclusive. They represent that
+	 * the particular type of value is up to date.  For example,
+	 *
+	 * 	a = 5		# NUMBER | NUMCUR
+	 * 	b = a ""	# Adds STRCUR to a, since a string value
+	 * 			# is now available. But the type hasn't changed!
+	 *
+	 * 	a = "42"	# STRING | STRCUR
+	 * 	b = a + 0	# Adds NUMCUR to a, since numeric value
+	 * 			# is now available. But the type hasn't changed!
+	 *
+	 * MAYBE_NUM is the joker.  It means "this is string data, but
+	 * the user may have really wanted it to be a number. If we have
+	 * to guess, like in a comparison, turn it into a number."
+	 * For example,    gawk -v a=42 ....
+	 * Here, `a' gets STRING|STRCUR|MAYBE_NUM and then when used where
+	 * a number is needed, it gets turned into a NUMBER and STRING
+	 * is cleared.
+	 *
+	 * WSTRCUR is for efficiency. If in a multibyte locale, and we
+	 * need to do something character based (substr, length, etc.)
+	 * we create the corresponding wide character string and store it,
+	 * and add WSTRCUR to the flags so that we don't have to do the
+	 * conversion more than once.
+	 *
+	 * We hope that the rest of the flags are self-explanatory. :-)
+	 */
 #		define	STRING	0x0002       /* assigned as string */
 #		define	STRCUR	0x0004       /* string value is current */
 #		define	NUMCUR	0x0008       /* numeric value is current */
diff --git a/mpfr.c b/mpfr.c
index a89b2bc6..4e4e12dc 100644
--- a/mpfr.c
+++ b/mpfr.c
@@ -347,7 +347,7 @@ mpg_force_number(NODE *n)
 		return n;
 
 	if ((n->flags & MAYBE_NUM) != 0) {
-		n->flags &= ~MAYBE_NUM;
+		n->flags &= ~(MAYBE_NUM|STRING);
 		newflags = NUMBER;
 	}
 
@@ -525,7 +525,7 @@ set_PREC()
 	if ((val->flags & MAYBE_NUM) != 0)
 		force_number(val);
 
-	if ((val->flags & (STRING|NUMBER)) == STRING) {
+	if ((val->flags & STRCUR) != 0) {
 		int i, j;
 
 		/* emulate IEEE-754 binary format */
diff --git a/node.c b/node.c
index de771147..a7c19db1 100644
--- a/node.c
+++ b/node.c
@@ -76,7 +76,7 @@ r_force_number(NODE *n)
 			return n;
 		} else if (n->stlen == 4 && is_ieee_magic_val(n->stptr)) {
 			if ((n->flags & MAYBE_NUM) != 0)
-				n->flags &= ~MAYBE_NUM;
+				n->flags &= ~(MAYBE_NUM|STRING);
 			n->flags |= NUMBER|NUMCUR;
 			n->numbr = get_ieee_magic_val(n->stptr);
 
@@ -103,7 +103,7 @@ r_force_number(NODE *n)
 
 	if ((n->flags & MAYBE_NUM) != 0) {
 		newflags = NUMBER;
-		n->flags &= ~MAYBE_NUM;
+		n->flags &= ~(MAYBE_NUM|STRING);
 	} else
 		newflags = 0;