Re: [PHP-DEV] Interaction between finally blocks and exit()
On Tue, Feb 23, 2021 at 5:12 PM Nikita Popov wrote: > On Tue, Feb 23, 2021 at 4:52 PM Guilliam Xavier > wrote: > >> On Fri, Feb 5, 2021 at 2:10 PM G. P. B. wrote: >> >> > Greetings internals, >> > >> > While working on rewriting the PHP docs about errors and error handling >> [1] >> > I came across a change of behaviour in an edge case of an edge case. >> > >> > finally blocks are meant to be always executed regardless that an >> Exception >> > has been thrown or not, which it does, however a call to exit() (or >> die() >> > as they are aliases). >> > This can be seen with the following example: https://3v4l.org/6Tger >> > >> > However, there is one case where finally blocks are executed when >> exit() is >> > used, namely when a generator has a finally block and exit() is called >> > during its traversal, an example of this in action can be seen here: >> > https://3v4l.org/HGKHS >> > >> > The behaviour of this edge case of an edge case is highly dependent on >> the >> > version of PHP where this is run, PHP 5.5, 5.6, 7.0, early version of >> PHP >> > 7.1, PHP 7.2.0, PHP 7.2.1, and PHP 8.0 all run the finally block on >> exit(). >> > Later versions of PHP 7.1, 7.2.2 and above and PHP 7.3 and 7.4 all skip >> the >> > finally block. >> > >> > Frankly this is already going to be a mess to document, but this begs >> the >> > question is there a "bug" in executing the finally blocks in generators >> > during a call to exit() or is the "bug" to not execute finally blocks >> when >> > exit() is called. >> > >> > I've CCed the PHP 8.0 RMs as if the consensus is that skipping finally >> > blocks after a call to exit() is performed it would be wise to change >> this >> > behaviour in PHP 8.0 only and land this ASAP, even though it's a BC >> break. >> > >> > Interested in hearing your thoughts. >> > >> > Best regards, >> > >> > George P. Banyard >> > >> > [1] https://github.com/php/doc-en/pull/320 >> > >> >> Hello again, >> >> From my message from two weeks ago, my understanding is that finally >> blocks >> are *never* supposed to be executed on exit(), and that there is indeed a >> bug (regression) with generators. >> >> With PHP 8.0.3RC1 having been released without any reply here from the >> people CCed, maybe you should open a bug report? >> > > Finally blocks are intended to be always executed when destructors are > executed. The fact that they are not yet executed for exit() outside > generators is a known bug. (For generators, finally is part of the > destructor, which is why the issue does not appear there.) > > Regards, > Nikita > Thanks for replying. So it seems that I had it all backwards ^^' For the record, this comment may help understanding: https://github.com/php/php-src/pull/5243#issuecomment-598664651 -- Guilliam Xavier
Re: [PHP-DEV] Interaction between finally blocks and exit()
On Tue, Feb 23, 2021 at 4:52 PM Guilliam Xavier wrote: > On Fri, Feb 5, 2021 at 2:10 PM G. P. B. wrote: > > > Greetings internals, > > > > While working on rewriting the PHP docs about errors and error handling > [1] > > I came across a change of behaviour in an edge case of an edge case. > > > > finally blocks are meant to be always executed regardless that an > Exception > > has been thrown or not, which it does, however a call to exit() (or die() > > as they are aliases). > > This can be seen with the following example: https://3v4l.org/6Tger > > > > However, there is one case where finally blocks are executed when exit() > is > > used, namely when a generator has a finally block and exit() is called > > during its traversal, an example of this in action can be seen here: > > https://3v4l.org/HGKHS > > > > The behaviour of this edge case of an edge case is highly dependent on > the > > version of PHP where this is run, PHP 5.5, 5.6, 7.0, early version of PHP > > 7.1, PHP 7.2.0, PHP 7.2.1, and PHP 8.0 all run the finally block on > exit(). > > Later versions of PHP 7.1, 7.2.2 and above and PHP 7.3 and 7.4 all skip > the > > finally block. > > > > Frankly this is already going to be a mess to document, but this begs the > > question is there a "bug" in executing the finally blocks in generators > > during a call to exit() or is the "bug" to not execute finally blocks > when > > exit() is called. > > > > I've CCed the PHP 8.0 RMs as if the consensus is that skipping finally > > blocks after a call to exit() is performed it would be wise to change > this > > behaviour in PHP 8.0 only and land this ASAP, even though it's a BC > break. > > > > Interested in hearing your thoughts. > > > > Best regards, > > > > George P. Banyard > > > > [1] https://github.com/php/doc-en/pull/320 > > > > Hello again, > > From my message from two weeks ago, my understanding is that finally blocks > are *never* supposed to be executed on exit(), and that there is indeed a > bug (regression) with generators. > > With PHP 8.0.3RC1 having been released without any reply here from the > people CCed, maybe you should open a bug report? > Finally blocks are intended to be always executed when destructors are executed. The fact that they are not yet executed for exit() outside generators is a known bug. (For generators, finally is part of the destructor, which is why the issue does not appear there.) Regards, Nikita
Re: [PHP-DEV] Interaction between finally blocks and exit()
On Fri, Feb 5, 2021 at 2:10 PM G. P. B. wrote: > Greetings internals, > > While working on rewriting the PHP docs about errors and error handling [1] > I came across a change of behaviour in an edge case of an edge case. > > finally blocks are meant to be always executed regardless that an Exception > has been thrown or not, which it does, however a call to exit() (or die() > as they are aliases). > This can be seen with the following example: https://3v4l.org/6Tger > > However, there is one case where finally blocks are executed when exit() is > used, namely when a generator has a finally block and exit() is called > during its traversal, an example of this in action can be seen here: > https://3v4l.org/HGKHS > > The behaviour of this edge case of an edge case is highly dependent on the > version of PHP where this is run, PHP 5.5, 5.6, 7.0, early version of PHP > 7.1, PHP 7.2.0, PHP 7.2.1, and PHP 8.0 all run the finally block on exit(). > Later versions of PHP 7.1, 7.2.2 and above and PHP 7.3 and 7.4 all skip the > finally block. > > Frankly this is already going to be a mess to document, but this begs the > question is there a "bug" in executing the finally blocks in generators > during a call to exit() or is the "bug" to not execute finally blocks when > exit() is called. > > I've CCed the PHP 8.0 RMs as if the consensus is that skipping finally > blocks after a call to exit() is performed it would be wise to change this > behaviour in PHP 8.0 only and land this ASAP, even though it's a BC break. > > Interested in hearing your thoughts. > > Best regards, > > George P. Banyard > > [1] https://github.com/php/doc-en/pull/320 > Hello again, >From my message from two weeks ago, my understanding is that finally blocks are *never* supposed to be executed on exit(), and that there is indeed a bug (regression) with generators. With PHP 8.0.3RC1 having been released without any reply here from the people CCed, maybe you should open a bug report? -- Guilliam Xavier
Re: [PHP-DEV] Interaction between finally blocks and exit()
Executing finally blocks after a die was discussed in https://externals.io/message/107497 "exit() via exception", but https://github.com/php/php-src/pull/5243 "Make exit() unwind properly" wasn't merged in 8.0, just https://github.com/php/php-src/pull/5768 "... (minimal version)". The change of behavior for https://3v4l.org/HGKHS "yield - finally" that occurred in PHP 7.1.14 and 7.2.2 is probably related to https://bugs.php.net/bug.php?id=75396 "Exit inside generator finally results in fatal error". Maybe the behavior changed back in PHP 8.0.0 because of an unexpected interaction of those two things? (adding Nikita to the CC list) -- Guilliam Xavier
Re: [PHP-DEV] Interaction between finally blocks and exit()
Interesting. I'm not sure there's a "correct" answer here, but FWIW on balance my feeling is the expectation that exit() will immediately terminate a script (registered shutdown functions and destructors aside) should take precedence over the expectation that finally blocks will always execute, just because if you've got an exit/die inside a try block, I think it is reasonable to expect that you have already done anything that needs to be done before you get there (i.e. that your intent is for nothing else to happen), or to consider it a bug (certainly eyebrow raising code smell) otherwise. It's not the kind of use case finally was conceptually intended to address. And unlike an explicitly declared and self contained shutdown function or destructor, this could lead to what is effectively shutdown code being far removed and in a seemingly-random place in the code in relation to where the exit call occurs, maybe in a different file and not obvious to track down. Dave On Fri, Feb 5, 2021 at 1:10 PM G. P. B. wrote: > Greetings internals, > > While working on rewriting the PHP docs about errors and error handling [1] > I came across a change of behaviour in an edge case of an edge case. > > finally blocks are meant to be always executed regardless that an Exception > has been thrown or not, which it does, however a call to exit() (or die() > as they are aliases). > This can be seen with the following example: https://3v4l.org/6Tger > > However, there is one case where finally blocks are executed when exit() is > used, namely when a generator has a finally block and exit() is called > during its traversal, an example of this in action can be seen here: > https://3v4l.org/HGKHS > > The behaviour of this edge case of an edge case is highly dependent on the > version of PHP where this is run, PHP 5.5, 5.6, 7.0, early version of PHP > 7.1, PHP 7.2.0, PHP 7.2.1, and PHP 8.0 all run the finally block on exit(). > Later versions of PHP 7.1, 7.2.2 and above and PHP 7.3 and 7.4 all skip the > finally block. > > Frankly this is already going to be a mess to document, but this begs the > question is there a "bug" in executing the finally blocks in generators > during a call to exit() or is the "bug" to not execute finally blocks when > exit() is called. > > I've CCed the PHP 8.0 RMs as if the consensus is that skipping finally > blocks after a call to exit() is performed it would be wise to change this > behaviour in PHP 8.0 only and land this ASAP, even though it's a BC break. > > Interested in hearing your thoughts. > > Best regards, > > George P. Banyard > > [1] https://github.com/php/doc-en/pull/320 >
