[erlang-questions] Erlang C NIF access to process struct

[Mikael Pettersson]

My PR should fix both issues with show_heap/1.  I wasn't aware the other
show_* BIFs had issues, I may take a look at them soonish.

There is no updated document for the tag scheme AFAIK, but reading
erts/emulator/beam/erl_term.h should, if you can decipher all #ifdefs and
macros, provide the current details.  The general principles remain the
same, but new types and alternatives have appeared, and existing ones may
have been reassigned.

On Mon, Nov 6, 2017 at 4:55 AM, Boshan Sun <sunboshan@REDACTED> wrote:

> Does your fix also fix the variable alignment issue as well? The variable
> is in the beginning of the next row now, and should be in the end of same
> row. Also can you fix hipe_bifs:show_estack/1, hipe_bifs:show_nstack/1,
> hipe_bifs:show_pcb/1? They all suffer the "off" issue.
>
> BTW, I just read your paper *A Staged Tag Scheme for Erlang* and it
> explains Erlang's tag scheme pretty well. Thanks for that. The paper was
> written in 2000 for R6B/R7A, just wondering do you guys have some updated
> paper regarding for current state of Erlang/OTP's tag scheme?
>
> Thanks!
>
> 2017-11-05 1:34 GMT-08:00 Mikael Pettersson <mikpelinux@REDACTED>:
>
>> The "off" table is due to a glitch in the output routine.  The too short
>> "H  E A P" banner is indeed a 32-vs-64 bit bug.  I fixed both in
>> https://github.com/erlang/otp/pull/1619.
>>
>> WRT accessing the current "struct process", I haven't looked in detail,
>> but in general the NIF interface wants to abstract away representational
>> details and replace them function calls (actual runtime function calls, not
>> just function-like macros).  I don't see direct accesses to "struct
>> process" fitting into that.
>>
>> On Sun, Nov 5, 2017 at 4:39 AM, Boshan Sun <sunboshan@REDACTED> wrote:
>>
>>> Hi all,
>>>
>>> In Erlang, you can use `hipe_bifs:show_heap(self()).` to debug the
>>> process's heap.
>>>
>>> From: 0x000000001ee5c6e0 to 0x000000001ee5c748
>>>  |         H E A P         |
>>>  |            Address |           Contents |
>>>  |--------------------|--------------------|
>>> 4 | 0x000000001ee5c6e0 | 0x000000000000004f |
>>> [] | 0x000000001ee5c6e8 | 0xfffffffffffffffb |
>>> 3 | 0x000000001ee5c6f0 | 0x000000000000003f |
>>> [4] | 0x000000001ee5c6f8 | 0x000000001ee5c6e1 |
>>>  |--------------------|--------------------|
>>>
>>> However the implementation is for 32-bits machine, and the table is kind
>>> of off for a 64-bits erlang.
>>>
>>> I want to write a C NIF to print similar heap information. What I need
>>> is the address of `process -> heap` and the heap size so I can get the
>>> heap's information.
>>>
>>> My question is, is there a way to get a pointer to the given process via
>>> pid in C NIF?
>>>
>>> In NIF doc there's enif_get_local_pid
>>> <http://erlang.org/doc/man/erl_nif.html#enif_get_local_pid> , how does
>>> this pid translate to the process pointer?
>>>
>>> Thanks!
>>>
>>> Boshan
>>>
>>>
>>> _______________________________________________
>>> erlang-questions mailing list
>>> erlang-questions@REDACTED
>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>
>>>
>>
>
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