zend_call_stack.c: AIX backend

[NattyNarwhal]

Uses pthread_getthrds_np (so requires pthread linked, by default on ZTS, needs to be added for NTS). The stack size part is weird, but works in testing.

An alternative approach is using procfs, but I didn't bother with this due to it not working on PASE (and the pthread approach works for the main thread too).

[devnexen]

question: do you need to update zend_call_stack_default_size() ?

[NattyNarwhal]

question: do you need to update zend_call_stack_default_size() ?

Good point; looks like based on measuring (on PASE), it looks like 192 KB for threads (IBM claims 96, but I think that's for 32-bit, so ifdef).

For the main thread, I think AIX sets a 32 MB stack limit in ulimit by default (which, ulimit could be measured as a fallback path perhaps), but I can't find a consistent source for that. PASE seems to default to unlimited which caps at 256 MB.

[devnexen]

Once you re done, Zend/stack_limits would need to be run (and stack_limits_010.phpt will need an update for sure). Nice to bring AIX support regardless 👍🏼.

[NattyNarwhal]

stack_limits_010.phpt will need an update for sure

The annoying thing is that the exact stack size returned for the main thread seems annoyingly variable between systems (at least on PASE with its default unlimited stack size) and thus I can't use an exact size. Not sure what the best strategy for that test is; round to some close enough number like page size?

[devnexen]

ah right ... in that case, the simplest would be to test ranges unless @arnaud-lb has a better suggestion :)

[arnaud-lb]

The annoying thing is that the exact stack size returned for the main thread seems annoyingly variable between systems (at least on PASE with its default unlimited stack size) and thus I can't use an exact size. Not sure what the best strategy for that test is; round to some close enough number like page size?

What is the size reported by zend_call_stack_get() when the stack size is unlimited? (I would expect the cap of 256MB?)

In stack_limit_010.phpt anything that allows to check that the stack size detection is not completely off would be good, but the most accurate the better. This test assumes a system with default settings.

[NattyNarwhal]

What is the size reported by zend_call_stack_get() when the stack size is unlimited? (I would expect the cap of 256MB?)

0xffffbe0 on one system, but on another system, I get a value like 0xffffed0. I'm assuming there's stuff on the top of the stack that's reserved by the system that gets taken off when reporting the stack size for the main thread. It's all pretty close to the limit.

(FWIW, if I try capping the stack value to AIX's default value of 32 MB, I also get the same variance, just capped at i.e. 0x1fffc40 vs. 0x1fffed0. So the variable amount is being taken off from the declared maximum value.)

[arnaud-lb]

Let's skip this test on AIX/PASE for now then

[NattyNarwhal]

Let's skip this test on AIX/PASE for now then

It needs an environment variable set, so it'll be skipped automatically, but I can add an explicit one in case

[arnaud-lb]

A condition based on PHP_OS_FAMILY in the --SKIPIF-- section would work?