Bug #79495 [Opn]: PHP fails to emit notices about undefined variables in switch expression

Edit report at https://bugs.php.net/bug.php?id=79495&edit=1 ID: 79495 Updated by: nikic@php.net Reported by: tandre@php.net Summary: PHP fails to emit notices about undefined variables in switch expression Status: Open Type: Bug Package: Output Control PHP Version: Next Major Version Block user comment: N Private report: N New Comment: A corollary is that you also get multiple undefined variable warnings if there are multiple cases: https://3v4l.org/B3snP Previous Comments: ------------------------------------------------------------------------ [2020-04-22 17:27:18] cmb@php.net If the switch body is empty, or has just a default clause, the switch is superfluous, and as such optimized away by the compiler (not OPcache). If there should be diagnostic message, it should be about the superfluous switch, not the irrelevant variable in the switch expression. ------------------------------------------------------------------------ [2020-04-19 17:46:01] tandre@php.net Description: ------------ PHP does not emit notices in switch where the only case is the default case (or where there are no cases) This can be fixed by Zend/zend_compile.c emitting a CHECK_VAR opcode when the temporary value is IS_CV (a compiled variable such as $undefSwitch), in the cases where: - there are no case statements - if the only case statement is the default case. Noticed in https://github.com/php/php-src/pull/5371#discussion_r410947575 https://bugs.php.net/bug.php?id=52426 is related, but it's from 2010 (php 5.2), and I expect opinions have changed since then, e.g. with https://wiki.php.net/rfc/engine_warnings getting approved Test script: --------------- <?php ini_set('display_errors', 'stderr'); error_reporting(E_ALL); echo $undefVar; // This does emit a notice switch($undefSwitch) {} // This does not emit a notice switch($undefSwitch2) { default: echo "default\n";} // This does not emit a notice Expected result: ---------------- PHP should emit an undefined variable notice for the two switch statements in the test script Actual result: -------------- PHP does not emit any notices for the two switch statements in the test script, in php 5.3, 5.6, 7.0, 7.4, and 8.0-dev Apparently, it did emit notices in 5.5 - https://bugs.php.net/bug.php?id=68105 suggests that emitting notices was the expected behavior for 5.5. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=79495&edit=1