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digitalmars.D.learn - Pass reference to void*

reply Andre Pany <andre s-e-a-p.de> writes:
Hi,

I call a C function from a dll (SO on linux). While the following 
code works
fine for DMD on windows, there are strange errors for LDC on 
windows. Also the equivalent code does not work for DMD/LDC on 
linux.
(When calling other functions from the dll and passing the model 
reference, this functions are failing).

Function "Open" gets a path to a model and return via argument 
pModel the reference.
I am not 100% sure whether I call function Open correctly in 
regards to the pModel
argument.

extern(C) nothrow  nogc
{
	alias Model = void*;

	alias da_Open = Status function(const(char)* path, Model* 
pModel);
}

__gshared {
	da_Open Open;
}

Open = cast(da_Open) GetProcAddress(h, "Open");
Model model;
string modelFilePath = "...";

auto status = Open(modelFilePath.toStringz, &model);

Is &model correct?

Kind regards
André
Jan 07 2019
parent reply Stefan Koch <uplink.coder googlemail.com> writes:
On Monday, 7 January 2019 at 12:19:57 UTC, Andre Pany wrote:

 Hi,

 I call a C function from a dll (SO on linux). While the 
 following code works
 fine for DMD on windows, there are strange errors for LDC on 
 windows. Also the equivalent code does not work for DMD/LDC on 
 linux.
 (When calling other functions from the dll and passing the 
 model reference, this functions are failing).

 [...]


 From the function declaration &model seems to be the correct 
thing to use here.
Have you checked that Open is not null ?
Jan 07 2019
parent reply Andre Pany <andre s-e-a-p.de> writes:
On Monday, 7 January 2019 at 13:01:57 UTC, Stefan Koch wrote:

 On Monday, 7 January 2019 at 12:19:57 UTC, Andre Pany wrote:

 Hi,

 I call a C function from a dll (SO on linux). While the 
 following code works
 fine for DMD on windows, there are strange errors for LDC on 
 windows. Also the equivalent code does not work for DMD/LDC on 
 linux.
 (When calling other functions from the dll and passing the 
 model reference, this functions are failing).

 [...]


 From the function declaration &model seems to be the correct 
 thing to use here.
 Have you checked that Open is not null ?


Yes, Open is not null and the strange thing is, everything is 
working fine for
DMD on windows. (I call a lot other dll functions afterwards).
By switching to LDC the subsequent calls to DLL functions are 
failing.

Thanks.

Kind regards
André
Jan 07 2019
parent reply Stefan Koch <uplink.coder googlemail.com> writes:
On Monday, 7 January 2019 at 13:15:44 UTC, Andre Pany wrote:

 On Monday, 7 January 2019 at 13:01:57 UTC, Stefan Koch wrote:

 On Monday, 7 January 2019 at 12:19:57 UTC, Andre Pany wrote:

 [...]


 From the function declaration &model seems to be the correct 
 thing to use here.
 Have you checked that Open is not null ?


 Yes, Open is not null and the strange thing is, everything is 
 working fine for
 DMD on windows. (I call a lot other dll functions afterwards).
 By switching to LDC the subsequent calls to DLL functions are 
 failing.

 Thanks.

 Kind regards
 André


Might be an calling convention issue?

Are they declared with extern(Windows) ?
Jan 09 2019
parent Andre Pany <andre s-e-a-p.de> writes:
On Wednesday, 9 January 2019 at 18:37:57 UTC, Stefan Koch wrote:

 On Monday, 7 January 2019 at 13:15:44 UTC, Andre Pany wrote:

 On Monday, 7 January 2019 at 13:01:57 UTC, Stefan Koch wrote:

 On Monday, 7 January 2019 at 12:19:57 UTC, Andre Pany wrote:

 [...]


 From the function declaration &model seems to be the correct 
 thing to use here.
 Have you checked that Open is not null ?


 Yes, Open is not null and the strange thing is, everything is 
 working fine for
 DMD on windows. (I call a lot other dll functions afterwards).
 By switching to LDC the subsequent calls to DLL functions are 
 failing.

 Thanks.

 Kind regards
 André


 Might be an calling convention issue?

 Are they declared with extern(Windows) ?


I finally got it solved. The d coding was right. There was an 
error in the dll which caused an issue for LDC on Windows.
The SO (linux) I got working by chance. The SO has some 
dependencies to a system package. After installing this package 
by chance on my Alpine, the cryptic error message disappeared and 
everything works fine.

Kind regards
Andre
Jan 09 2019