Bug #74569 [Com]: Return in a finally clause silently ignores an exception thrown in a try clause
Edit report at https://bugs.php.net/bug.php?id=74569&edit=1
ID: 74569
Comment by: olavisau at gmail dot com
Reported by: trianman at gmail dot com
Summary: Return in a finally clause silently ignores an
exception thrown in a try clause
Status: Open
Type: Bug
Package: Scripting Engine problem
Operating System: Any
PHP Version: 7.1.4
Block user comment: N
Private report: N
New Comment:
BC is broken with any solution. The fact that javascript behaves in the same way worries me.
It's probably very hard to implement. I agree with the E_NOTICE.
Previous Comments:
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[2017-05-11 14:21:03] trianman at gmail dot com
> btw The behaviour in PHP is the same as that which happens in Java
> This behaviour is also that used in Javascript.
Sorry to hear that, but AFAIK nor Java nor JavaScript (ECMAScript) has no conventional
(standartized) way to produce non critical warnings at the run time.
So PHP is better in this way and why can't we employ it?
> "Don't put returns in finally"
I believe that the good tool must help its users not to "shoot themselves" as much as
possible. So the user becomes free from a lot of "Don't do something somewhere". If
you don't agree you are free to use an assembler to do anything you want and remember a lot of
such restrictions.
I can imagine another more expectable an clear way to handle this case. But it will break a BC so
can be implemented only in a new major release of PHP.
Triggering E_NOTICE is the most convenient way for now.
------------------------------------------------------------------------
[2017-05-11 13:42:04] danack@php.net
This behaviour is also that used in Javascript.
function foo() {
try {
throw 42;
}
finally {
return "edge cases are hard";
}
};
alert(foo());
------------------------------------------------------------------------
[2017-05-11 13:30:49] danack@php.net
> but it MUST NOT be silently dropped out.
That's a conclusion without rigorous justification.
btw The behaviour in PHP is the same as that which happens in Java: https://web.archive.org/web/20070922061412/http://weblogs.java.net/blog/staufferjames/archive/2007/06/_dont_return_in.html
It'd be a lot easier to say "Don't put returns in finally blocks, yo".
> The interpreter should trigger an E_NOTICE or something similar here.
This would almost certainly be better done with code analysis tools, rather than giving warnings on
valid (though highly surprising) code.
------------------------------------------------------------------------
[2017-05-11 07:41:34] olavisau at gmail dot com
The correct way of writing this would be to catch the exception and throw it again, however this
also fails. If it is not thrown again, then the behavior is correct.
<?php
class MyException extends Exception
{
public function __construct($message = "", $code = 0, Throwable $previous = null)
{
parent::__construct($message, $code, $previous);
print "2. Exception constructed\n";
}
}
function throw_exception() {
try {
throw new MyException("5. Exception message\n");
} catch(Exception $exception) {
print "3. Exception caught and thrown again\n";
throw $exception;
} finally {
return "4. Return statement\n";
}
}
try {
print "1. Start\n";
print throw_exception();
} catch (Exception $e) {
print $e->getMessage();
}
The flow should be: exception is thrown, caught by the inner block, thrown again, caught by the
outer block and then the finally block should execute, returning the flow to
print throw_exception();
------------------------------------------------------------------------
[2017-05-10 16:44:47] trianman at gmail dot com
Description:
------------
Return in a finally clause silently ignores an exception thrown in a try clause.
I understand that there is no way to handle an exception here, but it MUST NOT be silently dropped
out.
The interpreter should trigger an E_NOTICE or something similar here.
Looks like any version of PHP from 5.6 to 7.1.4 behaves in the same manner: https://3v4l.org/C16rP
Here is a similar issue: https://bugs.php.net/bug.php?id=68270
Test script:
---------------
<?php
class MyException extends Exception
{
public function __construct($message = "", $code = 0, Throwable $previous = null)
{
print "2. Exception constructor\n";
parent::__construct($message, $code, $previous);
}
}
function ololo() {
try {
print "1. Start\n";
throw new MyException("4. Exception message\n");
} finally {
return "3. Return statement\n";
}
}
try {
print ololo();
} catch (Exception $e) {
print $e->getMessage();
}
Expected result:
----------------
1. Start
2. Exception constructor
PHP NOTICE: Dropped exception due the return statement in a finally block
3. Return statement
Actual result:
--------------
1. Start
2. Exception constructor
3. Return statement
------------------------------------------------------------------------
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