A time limit can be set on PHP script execution via `set_time_limit` (or .ini file).
When the time limit is reached, the OS will notify PHP and `timed_out` and `vm_interrupt`
flags are set. While these flags are regularly checked when executing PHP code, once the
end of the script is reached, they are not checked while invoking shutdown functions
(registered via `register_shutdown_function`).
Of course, if the shutdown functions are implemented *in* PHP, then the interrupt flag
will be checked while the VM is running PHP bytecode and the timeout will take effect.
But if the shutdown functions are built-in (implemented in C), it will not.
Since the shutdown functions are invoked through `zend_call_function`, add a check of the
`vm_interrupt` flag there. Then, the script time limit will be respected when *entering*
each shutdown function. The fact still remains that if a shutdown function is built-in and
runs for a long time, script execution will not time out until it finishes and the
interpreter tries to invoke the next one.
Still, the behavior of scripts with execution time limits will be more consistent after
this patch. To make the execution time-out feature work even more precisely, it would
be necessary to scrutinize all the built-in functions and add checks of the `vm_interrupt`
flag in any which can run for a long time. That might not be worth the effort, though.
It should be mentioned that this patch does not solely affect shutdown functions, neither
does it solely allow for interruption of running code due to script execution timeout.
Anything else which causes `vm_interrupt` to be set, such as the PHP interpreter receiving
a signal, will take effect when exiting from an internal function. And not just internal
functions which are called because they were registered to run at shutdown; there are
other cases where a series of internal functions might run in the midst of a script. In
all such cases, it will be possible to interrupt the interpreter now.
Closes GH-5543.
The 'int dummy' parameter to this function makes it appear that it was intended as a
signal handler, but it is not being used as such. So remove the redundant parameter.
get_gc() implementations that need to explore heterogeneous data
currently work by computing how many GC entries they need,
allocating a buffer for that and storing it on the object. This
is inefficient and wastes memory, because the buffer is retained
after the GC run.
This commit adds an API for a single global GC buffer, which can
be reused by get_gc implementations (as only one get_gc call is
ever active at the same time). The GC buffer will automatically
grow during the GC run and be discarded at the end.
Not NULLing the static_variables pointer for shadow methods during
static var shutdown would be a way to avoid this leak, but unless
there's evidence that inherited private methods with static vars are
actually a common use-case, I don't think we should keep this kind
of fragile edge-case optimization.
Fixes OSS-Fuzz #17875.
This is a fix for symfony/symfony#32995.
The behavior is:
* Throwing exception when loading parent/interface is allowed
(and we will also throw one if the class is simply not found).
* If this happens, the bucket key for the class is reset, so
it's possibly to try registering the same class again.
* However, if the class has already been used due to a variance
obligation, the exception is upgraded to a fatal error, as we
cannot safely unregister the class stub anymore.
The requirements for parent/interface are difference than for the
variance checks in type declarations. The latter can work on fully
unlinked classes, but the former need inheritance to be essentially
finished, only variance checks may still be outstanding.
Adding a new flag for this because we have lots of space, but we
could also represent these "inheritance states" more compactly in
the future.
symtable_cache_ptr now points to the first unused symtable_cache
entry, rahter than the last used one. This avoids taking a pointer
to the minus first element of the array, which is UB. Instead we
take a pointer to the end plus one, which is not UB.
Keep track of delayed variance obligations and check them after
linking a class is otherwise finished. Obligations may either be
unresolved method compatibility (because the necessecary classes
aren't available yet) or open parent/interface dependencies. The
latter occur because we allow the use of not fully linked classes
as parents/interfaces now.
An important aspect of the implementation is we do not require
classes involved in variance checks to be fully linked in order for
the class to be fully linked. Because the involved types do have to
exist in the class table (as partially linked classes) and we do
check these for correct variance, we have the guarantee that either
those classes will successfully link lateron or generate an error,
but there is no way to actually use them until that point and as
such no possibility of violating the variance contract. This is
important because it ensures that a class declaration always either
errors or will produce an immediately usable class afterwards --
there are no cases where the finalization of the class declaration
has to be delayed until a later time, as earlier variants of this
patch did.
Because variance checks deal with classes in various stages of
linking, we need to use a special instanceof implementation that
supports this, and also introduce finer-grained flags that tell us
which parts have been linked already and which haven't.
Class autoloading for variance checks is delayed into a separate
stage after the class is otherwise linked and before delayed
variance obligations are processed. This separation is needed to
handle cases like A extends B extends C, where B is the autoload
root, but C is required to check variance. This could end up
loading C while the class structure of B is in an inconsistent
state.
