fix & unify double-to-string conversion utils

Zend/tests/double_to_string.phpt

@@ -0,0 +1,66 @@
+--TEST--
+double to string conversion tests
+--FILE--
+<?php
+
+$doubles = array(
+	290000000000000000,
+	290000000000000,
+	29000000000000,
+	29000000000000.123123,
+	29000000000000.7123123,
+	29000.7123123,
+	239234242.7123123,
+	0.12345678901234567890,
+	10000000000000,
+	100000000000000,
+	1000000000000000001,
+	100000000000001,
+	10000000000,
+	999999999999999,
+	9999999999999999,
+	(float)0
+	);
+
+foreach ($doubles as $d) {
+	var_dump((string)$d);
+}
+
+echo "Done\n";
+?>
+--EXPECTF--	
+string(7) "2.9E+17"
+string(7) "2.9E+14"
+string(14) "29000000000000"
+string(14) "29000000000000"
+string(14) "29000000000001"
+string(13) "29000.7123123"
+string(15) "239234242.71231"
+string(16) "0.12345678901235"
+string(14) "10000000000000"
+string(7) "1.0E+14"
+string(7) "1.0E+18"
+string(7) "1.0E+14"
+string(11) "10000000000"
+string(7) "1.0E+15"
+string(7) "1.0E+16"
+string(1) "0"
+Done
+--UEXPECTF--
+unicode(7) "2.9E+17"
+unicode(7) "2.9E+14"
+unicode(14) "29000000000000"
+unicode(14) "29000000000000"
+unicode(14) "29000000000001"
+unicode(13) "29000.7123123"
+unicode(15) "239234242.71231"
+unicode(16) "0.12345678901235"
+unicode(14) "10000000000000"
+unicode(7) "1.0E+14"
+unicode(7) "1.0E+18"
+unicode(7) "1.0E+14"
+unicode(11) "10000000000"
+unicode(7) "1.0E+15"
+unicode(7) "1.0E+16"
+unicode(1) "0"
+Done

Zend/zend_operators.c

@@ -769,10 +769,24 @@ static UChar* zend_u_format_gdouble(double dnum, int ndigit, UChar *result)
 
 	p1 = zend_u_format_double(dnum, ndigit, &decpt, &sign, 1, buf1);
 	p2 = result;
-	if (sign)
+
+	if (sign) {
 		*p2++ = (UChar) 0x2d /*'-'*/;
-	for (i = ndigit - 1; i > 0 && p1[i] == (UChar) 0x30  /*'0'*/; i--)
-		ndigit--;
+	}
+	/* if decimal point position is less than precision, cut zeros only in fractional part */
+	if (decpt <= ndigit) {
+		i = ndigit - 1;
+		while (i > 0 && i >= decpt && p1[i] == (UChar) 0x30  /*'0'*/) {
+			ndigit--;
+			i--;
+		}
+	} else {
+	/* otherwise cut all trailing zeros */
+		for (i = ndigit - 1; i > 0 && p1[i] == (UChar) 0x30  /*'0'*/; i--) {
+			ndigit--;
+		}
+	}
+
 	if ((decpt >= 0 && decpt - ndigit > 4)
 		|| (decpt < 0 && decpt < -3)) {		/* use E-style */
 		decpt--;

Zend/zend_strtod.c

@@ -1719,7 +1719,14 @@ ZEND_API char * zend_dtoa(double _d, int mode, int ndigits, int *decpt, int *sig
 					if (value(d) > 0.5 + value(eps))
 						goto bump_up;
 					else if (value(d) < 0.5 - value(eps)) {
-						while(*--s == '0');
+						/* cut ALL traling zeros only if the number of chars is greater than precision
+						 * otherwise cut only extra zeros
+						 */
+						if (k < ndigits) {
+							while(*--s == '0' && (s - s0) > k);
+						} else {
+							while(*--s == '0');
+						}
 						s++;
 						goto ret1;
 					}