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digitalmars.D - DMD dll GC bug when calling a function from an interface that creates

reply Hipreme <msnmancini hotmail.com> writes:
I have some sample code:


```d
interface IFont
{
   IFont createFontWithSize(int size);
}
```

Main Code:

```d
import common;
class TTFFont : IFont
{
   IFont createFontWithSize(int size){return new TTFFont;}
}

export extern(System) IFont newFont()
{
   auto ret = new TTFFont();
   GC.addRoot(ret);
   return ret;
}
```

DLL Code:

```d
import common;

Runtime.initialize();
IFont function() newFont;
newFont = loadSymbol("newFont");
IFont myFont = newFont();
IFont otherFont = myFont.createFontWithSize(32); //Gets collected 
after some time
```


For it not get collected after some time, I actually need to put 
GC.addRoot inside the function `createFontWithSize`. This makes 
it literally unusable
Oct 26 2022
parent reply cc <cc nevernet.com> writes:
On Thursday, 27 October 2022 at 02:42:47 UTC, Hipreme wrote:

 For it not get collected after some time, I actually need to 
 put GC.addRoot inside the function `createFontWithSize`. This 
 makes it literally unusable


D DLLs each operate under a separate GC context from the main 
process, so anything `new`ed in a DLL may be collected if a 
reference to it isn't maintained there.  You can link them 
together so they share the same GC with something like this:

```d
// mydll.d
extern(C) {
	void gc_setProxy(void* p);
	void gc_clrProxy();
}
export void MyDLL_Initialize(void* gc) {
	gc_setProxy(gc);
}
export void MyDLL_Terminate() {
	gc_clrProxy();
}


// main.d
extern (C) {
	void* gc_getProxy();
}
void main() {
	MyDLL_Initialize(gc_getProxy()); // Share this process's GC with 
the DLL
	scope(exit) MyDLL_Terminate();
	/* do stuff */
}
```

Source: http://arsdnet.net/dlang.org/dll.html
Nov 02 2022
next sibling parent reply Adam D Ruppe <destructionator gmail.com> writes:
On Thursday, 3 November 2022 at 04:38:28 UTC, cc wrote:

 D DLLs each operate under a separate GC context from the main 
 process, so anything `new`ed in a DLL may be collected if a 
 reference to it isn't maintained there.  You can link them 
 together so they share the same GC with something like this:


This is only true on dmd windows (with ldc, you get a shared 
druntime to all mixed) and you don't have to set the proxy 
yourself - Runtime.loadLibrary does it for you.

But do make sure you are using Runtime.loadLibrary! SimpleDllMain 
alone i don't think does it.... so this might be hipreme's 
problem.


 Source: http://arsdnet.net/dlang.org/dll.html


This is an old copy of the website newer info on the d wiki.
Nov 03 2022
parent cc <cc nevernet.com> writes:
On Thursday, 3 November 2022 at 12:33:17 UTC, Adam D Ruppe wrote:

 This is only true on dmd windows (with ldc, you get a shared 
 druntime to all mixed)


Ah, that's another confusing difference to have to remember.  
Does the wiki have an up to date list of known compiler 
differences?  Searching for this usually gets me 11-year old 
stackoverflow threads.
Nov 03 2022
prev sibling parent reply Guillaume Piolat <first.last spam.org> writes:
On Thursday, 3 November 2022 at 04:38:28 UTC, cc wrote:

 D DLLs each operate under a separate GC context from the main 
 process, so anything `new`ed in a DLL may be collected if a 
 reference to it isn't maintained there.  You can link them 
 together so they share the same GC with something like this:


Ooooooh this explain so much strange bugs we had with D programs 
hosting D DLL.
Nov 03 2022
parent Imperatorn <johan_forsberg_86 hotmail.com> writes:
On Thursday, 3 November 2022 at 14:53:19 UTC, Guillaume Piolat 
wrote:

 On Thursday, 3 November 2022 at 04:38:28 UTC, cc wrote:

 D DLLs each operate under a separate GC context from the main 
 process, so anything `new`ed in a DLL may be collected if a 
 reference to it isn't maintained there.  You can link them 
 together so they share the same GC with something like this:


 Ooooooh this explain so much strange bugs we had with D 
 programs hosting D DLL.


Are you on the D Discord btw?
Nov 03 2022