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digitalmars.D.learn - Linux shared library loading/linking from C does not invoke (shared)

reply ichneumwn <idonotenjoyemail idonotenjoyemail.org> writes:
Dear all,

I was trying to invoke some D code from Python and ran into 
issues which I eventually traced back to a simple example on the 
D website itself :

https://dlang.org/articles/dll-linux.html

Particularly the section "Dynamically Loading a D DLL From a C 
Program"

In my case, and indeed already in 2013 
(https://forum.dlang.org/post/yeqyqaaguhngczlnvqnq forum.dlang.org), shared
static this does not get invoked

I normally use:
LDC - the LLVM D compiler (1.21.0):
   based on DMD v2.091.1 and LLVM 10.0.0   (under Linux)

but I also tried
DMD64 D Compiler v2.095.0

Is the solution suggested in the linked post the "canonical way"?

Where could one file a suggestion for an update to the 
documentation?

Cheers!

PS Enjoying my project in D especially how easy it is to get the 
same code to run under windows too
Jan 12 2021
next sibling parent reply Imperatorn <johan_forsberg_86 hotmail.com> writes:
On Tuesday, 12 January 2021 at 08:19:45 UTC, ichneumwn wrote:

 Where could one file a suggestion for an update to the 
 documentation?


In the top right section of the page you can click the "Improve 
this page"-link.
Jan 12 2021
parent ichneumwn <idonotenjoyemail idonotenjoyemail.org> writes:
On Tuesday, 12 January 2021 at 09:02:38 UTC, Imperatorn wrote:

 On Tuesday, 12 January 2021 at 08:19:45 UTC, ichneumwn wrote:

 Where could one file a suggestion for an update to the 
 documentation?


 In the top right section of the page you can click the "Improve 
 this page"-link.


Thanks, I will leave it though. I do not want to mess about and 
write about something I have just learnt in the last hour. That 
could do more damage than good.
Jan 12 2021
prev sibling parent reply ichneumwn <idonotenjoyemail idonotenjoyemail.org> writes:
On Tuesday, 12 January 2021 at 08:19:45 UTC, ichneumwn wrote:

 Dear all,

 I was trying to invoke some D code from Python and ran into 
 issues which I eventually traced back to a simple example on 
 the D website itself :

 https://dlang.org/articles/dll-linux.html

 Particularly the section "Dynamically Loading a D DLL From a C 
 Program"

 In my case, and indeed already in 2013 
 (https://forum.dlang.org/post/yeqyqaaguhngczlnvqnq forum.dlang.org), shared
static this does not get invoked

 I normally use:
 LDC - the LLVM D compiler (1.21.0):
   based on DMD v2.091.1 and LLVM 10.0.0   (under Linux)

 but I also tried
 DMD64 D Compiler v2.095.0

 Is the solution suggested in the linked post the "canonical 
 way"?

 Where could one file a suggestion for an update to the 
 documentation?

 Cheers!

 PS Enjoying my project in D especially how easy it is to get 
 the same code to run under windows too


Follow on to my own question: on Linux, with gcc, I have created 
the following file "starter.c" that I inject into my D shared 
library:

   int rt_init(void);
   int rt_term(void);

   // should really check for errors!
   static void __attribute__((constructor)) Dstarter(void) {
     rt_init();
   }

   static void __attribute__((destructor)) Dterminator(void) {
     rt_term();
   }

That seems to do the trick. Not sure how clean this is?
Jan 12 2021
parent reply Mike Parker <aldacron gmail.com> writes:
On Tuesday, 12 January 2021 at 09:31:08 UTC, ichneumwn wrote:


 Follow on to my own question: on Linux, with gcc, I have 
 created the following file "starter.c" that I inject into my D 
 shared library:

   int rt_init(void);
   int rt_term(void);

   // should really check for errors!
   static void __attribute__((constructor)) Dstarter(void) {
     rt_init();
   }

   static void __attribute__((destructor)) Dterminator(void) {
     rt_term();
   }

 That seems to do the trick. Not sure how clean this is?


You should be able to do the same in D with 
`pragma(crt_constructor)` and `pragma(crt_destructor)`:

https://dlang.org/spec/pragma.html#crtctor
https://dlang.org/spec/pragma.html#crtdtor
https://dlang.org/changelog/2.078.0.html#crt-constructor
Jan 12 2021
parent ichneumwn <idonotenjoyemail idonotenjoyemail.org> writes:
On Tuesday, 12 January 2021 at 09:49:46 UTC, Mike Parker wrote:

 On Tuesday, 12 January 2021 at 09:31:08 UTC, ichneumwn wrote:


 Follow on to my own question: on Linux, with gcc, I have 
 created the following file "starter.c" that I inject into my D 
 shared library:

   int rt_init(void);
   int rt_term(void);

   // should really check for errors!
   static void __attribute__((constructor)) Dstarter(void) {
     rt_init();
   }

   static void __attribute__((destructor)) Dterminator(void) {
     rt_term();
   }

 That seems to do the trick. Not sure how clean this is?


 You should be able to do the same in D with 
 `pragma(crt_constructor)` and `pragma(crt_destructor)`:

 https://dlang.org/spec/pragma.html#crtctor
 https://dlang.org/spec/pragma.html#crtdtor
 https://dlang.org/changelog/2.078.0.html#crt-constructor


Perfect, thanks! Interestingly, as I removed the C stub and tried 
the D route, I noticed that just calling rt_init() is enough to 
also get static ~this() to run on exit. In fact then adding 
writeln in a pragma(crt_destructor) function shows that it gets 
called after static ~this().

For anyone stumbling across this thread and looking for the 
import for rt_init/term:

import core.runtime : rt_init, rt_term;
Jan 12 2021