Fixed GH-16236: Fixed a bug in BcMath\Number::pow() and bcpow() when raising negative powers of 0.

ext/bcmath/bcmath.c

@@ -615,7 +615,10 @@ PHP_FUNCTION(bcpow)
 		goto cleanup;
 	}
 
-	bc_raise(first, exponent, &result, scale);
+	if (!bc_raise(first, exponent, &result, scale)) {
+		zend_throw_exception_ex(zend_ce_division_by_zero_error, 0, "Negative power of zero");
+		goto cleanup;
+	}
 
 	RETVAL_NEW_STR(bc_num2str_ex(result, scale));
 
@@ -1141,7 +1144,10 @@ static zend_result bcmath_number_pow_internal(
 		}
 		return FAILURE;
 	}
-	bc_raise(n1, exponent, ret, *scale);
+	if (!bc_raise(n1, exponent, ret, *scale)) {
+		zend_throw_exception_ex(zend_ce_division_by_zero_error, 0, "Negative power of zero");
+		return FAILURE;
+	}
 	bc_rm_trailing_zeros(*ret);
 	if (scale_expand) {
 		size_t diff = *scale - (*ret)->n_scale;

ext/bcmath/libbcmath/src/bcmath.h

@@ -173,7 +173,7 @@ typedef enum {
 
 raise_mod_status bc_raisemod(bc_num base, bc_num exponent, bc_num mod, bc_num *result, size_t scale);
 
-void bc_raise(bc_num base, long exponent, bc_num *resul, size_t scale);
+bool bc_raise(bc_num base, long exponent, bc_num *result, size_t scale);
 
 void bc_raise_bc_exponent(bc_num base, bc_num exponent, bc_num *resul, size_t scale);
 

ext/bcmath/libbcmath/src/raise.c

@@ -40,10 +40,10 @@ void bc_square_ex(bc_num n1, bc_num *result, size_t scale_min) {
 	*(result) = square_ex;
 }
 
-/* Raise NUM1 to the NUM2 power.  The result is placed in RESULT.
-   Maximum exponent is LONG_MAX.  If a NUM2 is not an integer,
+/* Raise "base" to the "exponent" power.  The result is placed in RESULT.
+   Maximum exponent is LONG_MAX.  If a "exponent" is not an integer,
    only the integer part is used.  */
-void bc_raise(bc_num num1, long exponent, bc_num *result, size_t scale) {
+bool bc_raise(bc_num base, long exponent, bc_num *result, size_t scale) {
 	bc_num temp, power;
 	size_t rscale;
 	size_t pwrscale;
@@ -54,7 +54,7 @@ void bc_raise(bc_num num1, long exponent, bc_num *result, size_t scale) {
 	if (exponent == 0) {
 		bc_free_num (result);
 		*result = bc_copy_num(BCG(_one_));
-		return;
+		return true;
 	}
 
 	/* Other initializations. */
@@ -64,12 +64,12 @@ void bc_raise(bc_num num1, long exponent, bc_num *result, size_t scale) {
 		rscale = scale;
 	} else {
 		is_neg = false;
-		rscale = MIN (num1->n_scale * exponent, MAX(scale, num1->n_scale));
+		rscale = MIN (base->n_scale * exponent, MAX(scale, base->n_scale));
 	}
 
 	/* Set initial value of temp. */
-	power = bc_copy_num(num1);
-	pwrscale = num1->n_scale;
+	power = bc_copy_num(base);
+	pwrscale = base->n_scale;
 	while ((exponent & 1) == 0) {
 		pwrscale = 2 * pwrscale;
 		bc_square_ex(power, &power, pwrscale);
@@ -92,14 +92,19 @@ void bc_raise(bc_num num1, long exponent, bc_num *result, size_t scale) {
 
 	/* Assign the value. */
 	if (is_neg) {
-		bc_divide(BCG(_one_), temp, result, rscale);
+		if (bc_divide(BCG(_one_), temp, result, rscale) == false) {
+			bc_free_num (&temp);
+			bc_free_num (&power);
+			return false;
+		}
 		bc_free_num (&temp);
 	} else {
 		bc_free_num (result);
 		*result = temp;
 		(*result)->n_scale = MIN(scale, (*result)->n_scale);
 	}
 	bc_free_num (&power);
+	return true;
 }
 
 /* This is used internally by BCMath */

ext/bcmath/tests/bcpow.phpt

@@ -60,17 +60,17 @@ Number "-9" (scale 0)
 
 Number "0" (scale 0)
 0 ** 15                             = 0
-0 ** -15                            = 0
+0 ** -15                            = Negative power of zero
 0 ** 1                              = 0
-0 ** -9                             = 0
+0 ** -9                             = Negative power of zero
 0 ** 0                              = 1
 0 ** -0                             = 1
 
 Number "-0" (scale 0)
 -0 ** 15                             = 0
--0 ** -15                            = 0
+-0 ** -15                            = Negative power of zero
 -0 ** 1                              = 0
--0 ** -9                             = 0
+-0 ** -9                             = Negative power of zero
 -0 ** 0                              = 1
 -0 ** -0                             = 1
 
@@ -188,17 +188,17 @@ Number "-9" (scale 10)
 
 Number "0" (scale 10)
 0 ** 15                             = 0.0000000000
-0 ** -15                            = 0.0000000000
+0 ** -15                            = Negative power of zero
 0 ** 1                              = 0.0000000000
-0 ** -9                             = 0.0000000000
+0 ** -9                             = Negative power of zero
 0 ** 0                              = 1.0000000000
 0 ** -0                             = 1.0000000000
 
 Number "-0" (scale 10)
 -0 ** 15                             = 0.0000000000
--0 ** -15                            = 0.0000000000
+-0 ** -15                            = Negative power of zero
 -0 ** 1                              = 0.0000000000
--0 ** -9                             = 0.0000000000
+-0 ** -9                             = Negative power of zero
 -0 ** 0                              = 1.0000000000
 -0 ** -0                             = 1.0000000000
 

ext/bcmath/tests/bcpow_div_by_zero.phpt

@@ -0,0 +1,29 @@
+--TEST--
+bcpow() negative power of zero
+--EXTENSIONS--
+bcmath
+--INI--
+bcmath.scale=0
+--FILE--
+<?php
+$exponents = ["-15", "-1", "-9"];
+$baseNumbers = ['0', '-0'];
+
+foreach ($baseNumbers as $baseNumber) {
+    foreach ($exponents as $exponent) {
+        try {
+            echo bcpow($baseNumber, $exponent), "\n";
+        } catch (Error $e) {
+            echo $e->getMessage(), "\n";
+        }
+    }
+}
+
+?>
+--EXPECT--
+Negative power of zero
+Negative power of zero
+Negative power of zero
+Negative power of zero
+Negative power of zero
+Negative power of zero

ext/bcmath/tests/number/methods/pow_div_by_zero.phpt

@@ -0,0 +1,41 @@
+--TEST--
+BcMath\Number pow(): negative power of zero
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+
+$values = [0, '0'];
+
+$exponents = [
+    [-3, 'int'],
+    ['-2', 'string'],
+    [new BcMath\Number('-2'), 'object'],
+];
+
+foreach ($values as $value) {
+    $num = new BcMath\Number($value);
+
+    foreach ($exponents as [$exponent, $type]) {
+        echo "{$value} ** {$exponent}: {$type}\n";
+        try {
+            $num->pow($exponent);
+        } catch (Error $e) {
+            echo $e->getMessage() . "\n";
+        }
+    }
+}
+?>
+--EXPECT--
+0 ** -3: int
+Negative power of zero
+0 ** -2: string
+Negative power of zero
+0 ** -2: object
+Negative power of zero
+0 ** -3: int
+Negative power of zero
+0 ** -2: string
+Negative power of zero
+0 ** -2: object
+Negative power of zero

ext/bcmath/tests/number/operators/pow_div_by_zero.phpt

@@ -0,0 +1,41 @@
+--TEST--
+BcMath\Number pow: negative power of zero by operator
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+
+$values = [0, '0'];
+
+$exponents = [
+    [-3, 'int'],
+    ['-2', 'string'],
+    [new BcMath\Number('-2'), 'object'],
+];
+
+foreach ($values as $value) {
+    $num = new BcMath\Number($value);
+
+    foreach ($exponents as [$exponent, $type]) {
+        echo "{$value} ** {$exponent}: {$type}\n";
+        try {
+            $num ** $exponent;
+        } catch (Error $e) {
+            echo $e->getMessage() . "\n";
+        }
+    }
+}
+?>
+--EXPECT--
+0 ** -3: int
+Negative power of zero
+0 ** -2: string
+Negative power of zero
+0 ** -2: object
+Negative power of zero
+0 ** -3: int
+Negative power of zero
+0 ** -2: string
+Negative power of zero
+0 ** -2: object
+Negative power of zero

ext/bcmath/tests/run_bcmath_tests_function.inc

@@ -13,11 +13,16 @@ function run_bcmath_tests(
         foreach ($firstTerms as $firstTerm) {
             echo "Number \"$firstTerm\" (scale $scale)\n";
             foreach ($secondTerms as $secondTerm) {
+                try {
+                    $ret = $bcmath_function($firstTerm, $secondTerm, $scale);
+                } catch (Throwable $e) {
+                    $ret = $e->getMessage();
+                }
                 echo $firstTerm,
                     " $symbol ",
                     str_pad($secondTerm, STRING_PADDING),
                     " = ",
-                    $bcmath_function($firstTerm, $secondTerm, $scale),
+                    $ret,
                     "\n";
             }
             echo "\n";