Added early return case when result is 0 (php#16697)

fixes php#16265
closes php#16697

Author: SakiTakamachi

NEWS

@@ -2,6 +2,10 @@ PHP                                                                        NEWS
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 ?? ??? ????, PHP 8.4.0RC4
 
+- BcMath:
+  . Fixed bug GH-16265 (Added early return case when result is 0)
+    (Saki Takamachi).
+
 - Core:
   . Fixed bug GH-16574 (Incorrect error "undefined method" messages).
     (nielsdos)

ext/bcmath/libbcmath/src/div.c

@@ -444,6 +444,11 @@ bool bc_divide(bc_num numerator, bc_num divisor, bc_num *quot, size_t scale)
 	/* Length of numerator data that can be read */
 	size_t numerator_readable_len = numeratorend - numeratorptr + 1;
 
+	if (divisor_len > numerator_readable_len + numerator_bottom_extension) {
+		*quot = bc_copy_num(BCG(_zero_));
+		return true;
+	}
+
 	/* If divisor is 1 here, return the result of adjusting the decimal point position of numerator. */
 	if (divisor_len == 1 && *divisorptr == 1) {
 		if (numerator_len == 0) {

ext/bcmath/tests/gh16265.phpt

@@ -0,0 +1,12 @@
+--TEST--
+GH-16265 Segmentation fault (index oob) in ext/bcmath/libbcmath/src/convert.c:155
+--EXTENSIONS--
+bcmath
+--INI--
+bcmath.scale=0
+--FILE--
+<?php
+echo bcdiv('-0.01', -12.3456789000e10, 9);
+?>
+--EXPECT--
+0.000000000