Hi All,
This topic has been discussed a couple of times before:
- http://marc.info/?t=138118341600002&r=1&w=2
- http://marc.info/?t=142708828500001&r=1&w=2
- http://marc.info/?t=143798102800002&r=1&w=2
I was inspired to revive the topic by this bug report:
https://bugs.php.net/bug.php?id=75056&edit=3
Currently, the backtrace of an Exception stores the following:
- function: string
- line: integer
- file: string
- class: string
- type: string
- args: array
This is effectively the same as debug_backtrace() with neither
DEBUG_BACKTRACE_PROVIDE_OBJECT nor DEBUG_BACKTRACE_IGNORE_ARGS set.
The "args" part of this contains full object references to anything that
happens to have been a function argument in the stack, and causes two
problems:
- Serializing an exception can fail, because some of these referenced
objects may be non-serializable (e.g. SimpleXMLElement, PDO).
- Destructors for these objects do not fire until the Exception is
destructed, causing resources to be held open unexpectedly after the
stack has been unwound. (The only other place I know of destructors
being unreliable in PHP is if there are circular references, in which
case the destructor will only fire when the GC detects the cycle.)
Both effects are almost entirely unpredictable, because it depends if
the object happens to have been a parameter in the current stack, rather
than a local variable or $this reference.
The simplest solution would be to simply remove this 'args' key from the
backtraces, as when DEBUG_BACKTRACE_IGNORE_ARGS is set on
debug_backtrace(). This would mean that any normal exception would hold
no object references, so would not extend any lifetimes, and would not
trigger any serialization errors.
Obviously, this has the downside of breaking any code that makes use of
this array; if anyone has examples of practical uses for it I would be
grateful to see them, and whether a compromise such as storing the class
name but not the object would be useful.
Regards,
--
Rowan Collins
[IMSoP]
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php
