Bug #78878 [NEW]: Buffer underflow in bc_shift_addsub

From: thomas-josef dot riedmaier at siemens dot com Operating system: Windows PHP version: 7.4.0 Package: BC math related Bug Type: Bug Bug description:Buffer underflow in bc_shift_addsub Description: ------------ When executing the test snippet below, a buffer underflow occurs in bc_shift_addsub. I theory, bc_shift_addsub's assert statement would be triggered, but this does not play any role in the official windows release binaries https://windows.php.net/downloads/releases/php-7.4.0-Win32-vc15-x64.zip . Instead, on our test machines, an ACCESS_VIOLATION is triggered. Test script: --------------- <?php print bcmul(²6483605105519922841849335928742092, bcpowmod(2, 65535, -4e-4)); -- Edit bug report at https://bugs.php.net/bug.php?id=78878&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=78878&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=78878&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=78878&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=78878&r=needscript Try newer version: https://bugs.php.net/fix.php?id=78878&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=78878&r=support Expected behavior: https://bugs.php.net/fix.php?id=78878&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=78878&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=78878&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=78878&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=78878&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=78878&r=dst IIS Stability: https://bugs.php.net/fix.php?id=78878&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=78878&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=78878&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=78878&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=78878&r=mysqlcfg