[erlang-bugs] nif reload

[Tony Rogvall]

Hi!

I have something strange niff stuff going on, I think.
(tested R17/R16)

I have a very simple demo nif application (attached), one function (not really needed) and
a nif that I want to be able to load/upgrade/unload. I have removed the reload callback,
that according to documentation is deprecated.

Following sequence can be seen, when I repeat the 
> l(niffy).
from the erlang shell.


Eshell V6.1  (abort with ^G)
1> niffy:hello().
Loading: ./niffy/priv/niffy_drv
c_src/niffy_nif.c:61: niffy_load: *priv_data=0x0 ptr=0x1e1820e8, ptr->n
c_src/niffy_nif.c:51: niffy_hello: priv_data=0x1e1820e8
world
2> niffy:hello().
c_src/niffy_nif.c:51: niffy_hello: priv_data=0x1e1820e8
world
3> l(niffy).
Loading: ./niffy/priv/niffy_drv
c_src/niffy_nif.c:72: niffy_upgrade: *priv_data=0x0 *old_priv_data=0x1e1820e8 ptr->n=1
{module,niffy}
4> niffy:hello().
c_src/niffy_nif.c:51: niffy_hello: priv_data=0x1e1820e8
world
5> l(niffy).     
c_src/niffy_nif.c:81: niffy_unload: priv_data=0x1e1820e8 ptr->n=2
Loading: ./niffy/priv/niffy_drv
c_src/niffy_nif.c:72: niffy_upgrade: *priv_data=0x0 *old_priv_data=0x1e1820e8 ptr->n=504889344
{module,niffy}
6> 
6> l(niffy).
c_src/niffy_nif.c:81: niffy_unload: priv_data=0x1e1820e8 ptr->n=504889345
Loading: ./niffy/priv/niffy_drv
c_src/niffy_nif.c:72: niffy_upgrade: *priv_data=0x0 *old_priv_data=0x1e1820e8 ptr->n=504889344
{module,niffy}
7> l(niffy).
c_src/niffy_nif.c:81: niffy_unload: priv_data=0x1e1820e8 ptr->n=504889345
Segmentation fault: 11

I can see that the unload is called and I free the priv_data, then upgrade is called on that very same memory.
But why? 






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