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	Sat, 28 Jan 2023 03:28:59 -0800 (PST)
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Date:	Sat, 28 Jan 2023 06:28:57 -0500
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Subject:	Re: Linking DXE3 with libraries
To:	djgpp AT delorie DOT com
References:	<496da509-6d4f-88a1-e94a-6c330a915f05 AT iki DOT fi>
From:	"Frank Sapone (emoaddict15 AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
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Good Morning Andris,

> - DXE loader has no way to found symbols of running executable (which 
> requests to load DXE) unless one tells where they are located
>
Correct, you need a DXE_EXPORT_TABLE with DXE_EXPORT(func/var) to 
resolve at run time.  See 
https://bitbucket.org/neozeed/q2dos/src/master/dos/dxe.c for an example 
if interested.
> - linking DXE directly with libraries (like libstdcxx.a or libc.a) 
> will cause duplicate copy of symbols. That is going to cause problems 
> when library have global state. I have seen similar problems, which 
> have often caused crash of program) for example in Linux, when direct 
> of indirect dependencies causes 2 different versions of shared library 
> to be loaded:
I'm not quite sure how it works exactly, but with C we just resolve 
everything like above, which seems to be the correct way.  With C++ 
things are trickier and we have to do -lstdcxx -lgcc or we get mangled 
names that can't even be exported.
> - are constructors and destructors of global objects executed, when 
> these objects belong to DXE? It seems from source code, that they 
> could. It is perhaps safer to verify that it actually works
>
I believe so, yes.
>
> I think one should avoid linking DXE with library directly, but 
> provide symbol list generated by DXE3RES (or manually) instead. 
> Exception could be if DXE module is only user of library, but program 
> itself does not use it
>
>
OK, but how do we deal with with the above C++ problem?

I will say that considering it is DOS the likliehood of someone swapping 
DXEs around is pretty slim, but I understand why you want to make it 
right.  I'd love to contribute code or even something insightful to 
these problems but I am not a compiler/compiler tools programmer.  I 
also apologize in advance for any dumb or obvious questions I may ask as 
a result of this conversation.  I just DXE3GEN like I have been for 
years and use the DXE_EXPORT... stuff to resolve at runtime.  This works 
quite well for C programs, but C++ requires additional work and it's not 
obvious what to do.

Frank

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