Don't use fp arithmetic for int results

# FP arithmetic is not accurate enough on 64-bit archs
# This patch relies on ZEND_SIGNED_MULTIPLY_LONG(),
# so that should be fixed as well.

1 files changed, 29 insertions, 12 deletions

diff --git a/ext/standard/math.c b/ext/standard/math.c
index 6d58ba54df..262ec23e1d 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -23,6 +23,7 @@
 
 #include "php.h"
 #include "php_math.h"
+#include "zend_multiply.h"
 
 #include <math.h>
 #include <float.h>
@@ -449,22 +450,38 @@ PHP_FUNCTION(pow)
 	convert_scalar_to_number(zexp TSRMLS_CC);
 
 	/* if both base and exponent were longs, we'll try to get a long out */
-	wantlong = Z_TYPE_P(zbase) == IS_LONG 
-	        && Z_TYPE_P(zexp ) == IS_LONG && Z_LVAL_P(zexp) >= 0;
+	if (Z_TYPE_P(zbase) == IS_LONG && Z_TYPE_P(zexp) == IS_LONG && Z_LVAL_P(zexp) >= 0) {
+		long l1 = 1, l2 = Z_LVAL_P(zbase), i = Z_LVAL_P(zexp);
+		
+		if (i == 0) {
+			RETURN_LONG(1L);
+		} else if (l2 == 0) {
+			RETURN_LONG(0);
+		}
+
+		/* calculate pow(long,long) in O(log exp) operations, bail if overflow */
+		while (i >= 1) {
+			int overflow;
+			double dval;
 
+			if (i % 2) {
+				--i;
+				ZEND_SIGNED_MULTIPLY_LONG(l1,l2,l1,dval,overflow);
+				if (overflow) RETURN_DOUBLE(dval * pow(l2,i));
+			} else {
+				i /= 2;
+				ZEND_SIGNED_MULTIPLY_LONG(l2,l2,l2,dval,overflow);
+				if (overflow) RETURN_DOUBLE((double)l1 * pow(dval,i));
+			}
+			if (i == 0) {
+				RETURN_LONG(l1);
+			}
+		}
+	}
 	convert_to_double(zbase);
 	convert_to_double(zexp);
 	
-	/* go ahead and calculate things. */
-	dval = pow(Z_DVAL_P(zbase),Z_DVAL_P(zexp));
-
-	/* if we wanted a long, and dval < LONG_MAX, it must be a long. */
-	if (wantlong && zend_finite(dval) && dval <= (double)LONG_MAX) {
-		RETURN_LONG((long)dval);
-	}
-
-	/* otherwise just return the double. */
-	RETURN_DOUBLE(dval);
+	RETURN_DOUBLE( pow(Z_DVAL_P(zbase),Z_DVAL_P(zexp)) );
 }
 /* }}} */