Bug #68797 [NEW]: Number 2.2250738585072012e-308 converted incorrectly

From: exploringbinary at gmail dot com Operating system: Windows PHP version: 5.5.20 Package: Math related Bug Type: Bug Bug description:Number 2.2250738585072012e-308 converted incorrectly Description: ------------ The conversion of the number 2.2250738585072012e-308 (equivalent to DBL_MIN) to double-precision floating-point is done incorrectly; it is one ULP too low. It prints back as 2.2250738585072009E-308; it should be 2.2250738585072014e-308 (DBL_MIN). (The nearby decimal numbers 2.2250738585072013e-308, 2.2250738585072014e-308, 2.2250738585072015e-308, and 2.2250738585072016e-308 all convert correctly to DBL_MIN.) This is likely due to PHP's old copy of David Gay's dtoa.c; see these change entries at http://www.netlib.org/fp/changes -- they are probably what is needed: Wed Feb 12 00:40:01 EST 1997 dtoa.c: strtod: on IEEE systems, scale to avoid intermediate underflows when the result does not underflow; compiling with -DNO_IEEE_Scale restores the old logic. Fix a bug, revealed by input string 2.2250738585072012e-308, in treating input just less than the smallest normalized number. (The bug introduced an extra ULP of error in this special case.) Fri May 15 07:49:07 EDT 1998 dtoa.c: strtod: fix another glitch with scaling to avoid underflow with IEEE arithmetic, again revealed by the input string 2.2250738585072012e-308, which was rounded to the largest denormal rather than the smallest normal double precision number. Test script: --------------- <?php ini_set("precision", "17"); echo 2.2250738585072012e-308; ?> Expected result: ---------------- 2.2250738585072014e-308 Actual result: -------------- 2.2250738585072009E-308 -- Edit bug report at https://bugs.php.net/bug.php?id=68797&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=68797&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=68797&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=68797&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=68797&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=68797&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=68797&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=68797&r=needscript Try newer version: https://bugs.php.net/fix.php?id=68797&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=68797&r=support Expected behavior: https://bugs.php.net/fix.php?id=68797&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=68797&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=68797&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=68797&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=68797&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=68797&r=dst IIS Stability: https://bugs.php.net/fix.php?id=68797&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=68797&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=68797&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=68797&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=68797&r=mysqlcfg