www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Dynamically calling shared objects from statically build executable

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

while dynamically calling a shared object from a statically
build executable on linux, both LDC and DMD fails with a
non-zero code 139.

In my productive system the SO is written in C++,
for reproduction I wrote a sample SO in D.

You can find the example here
https://github.com/ldc-developers/ldc/issues/3310


Is this a bug with LDC and DMD, or is it not allowed
to dynamically call a SO from a statically build executable on 
linux?

Background: The SO file I get from third party, while the 
executable
I develop. I need to run the executable on a distroless docker 
image (SCRATCH),
therefore I try to reduce system dependencies on my side by 
building a static executable.

PS. DMD even fails without the static switch with:
Aborting from src/rt/sections_elf_shared.d(480) DSO being 
unregistered isn't current last one.

Kind regards
André
Feb 09 2020
parent reply Ernesto Castellotti <mail ernestocastellotti.it> writes:
On Monday, 10 February 2020 at 04:41:31 UTC, Andre Pany wrote:

 Is this a bug with LDC and DMD, or is it not allowed
 to dynamically call a SO from a statically build executable on 
 linux


On Unix systems it is not possible to dynamically load a library 
shared by a static executable, I don't know if it works 
differently for Windows.

This is because it is absolutely necessary to link libdl 
dynamically, you cannot link static.

For GNU/Linux systems there is this alternative to dlopen/dlsym 
that does not require dynamic link: 
https://www.gnu.org/software/libtool/manual/html_node/Dlpreopening.html
Feb 10 2020
parent reply Andre Pany <andre s-e-a-p.de> writes:
On Monday, 10 February 2020 at 13:14:50 UTC, Ernesto Castellotti 
wrote:

 On Monday, 10 February 2020 at 04:41:31 UTC, Andre Pany wrote:

 Is this a bug with LDC and DMD, or is it not allowed
 to dynamically call a SO from a statically build executable on 
 linux


 On Unix systems it is not possible to dynamically load a 
 library shared by a static executable, I don't know if it works 
 differently for Windows.

 This is because it is absolutely necessary to link libdl 
 dynamically, you cannot link static.

 For GNU/Linux systems there is this alternative to dlopen/dlsym 
 that does not require dynamic link: 
 https://www.gnu.org/software/libtool/manual/html_node/Dlpreopening.html


This is a topic I almost have no knowledge, therefore a question.

If I understand this StackOverflow question correctly, it is 
possible to call dynamically a shared object from a static 
library (with dlopen):

https://stackoverflow.com/questions/17862272/dlopen-a-dynamic-library-from-a-static-library-linux-c

But I understand from you it is not possible dynamically call a 
shared object from a static executable.

Therefore it works for static libraries but not for statically 
executables?

Kind regards
Andre
Feb 10 2020
parent reply Ernesto Castellotti <erny.castell gmail.com> writes:
On Monday, 10 February 2020 at 19:00:36 UTC, Andre Pany wrote:

 On Monday, 10 February 2020 at 13:14:50 UTC, Ernesto 
 Castellotti wrote:

 On Monday, 10 February 2020 at 04:41:31 UTC, Andre Pany wrote:

 Is this a bug with LDC and DMD, or is it not allowed
 to dynamically call a SO from a statically build executable 
 on linux


 On Unix systems it is not possible to dynamically load a 
 library shared by a static executable, I don't know if it 
 works differently for Windows.

 This is because it is absolutely necessary to link libdl 
 dynamically, you cannot link static.

 For GNU/Linux systems there is this alternative to 
 dlopen/dlsym that does not require dynamic link: 
 https://www.gnu.org/software/libtool/manual/html_node/Dlpreopening.html


 This is a topic I almost have no knowledge, therefore a 
 question.

 If I understand this StackOverflow question correctly, it is 
 possible to call dynamically a shared object from a static 
 library (with dlopen):

 https://stackoverflow.com/questions/17862272/dlopen-a-dynamic-library-from-a-static-library-linux-c

 But I understand from you it is not possible dynamically call a 
 shared object from a static executable.

 Therefore it works for static libraries but not for statically 
 executables?

 Kind regards
 Andre


Static libraries are simple collections of object files, there is 
no difference between linking a static library or several object 
files

If you notice when going to compile the executable linka libdl 
and the static library, then the executable will be linked to 
dynamic library and will not be a static executable.
Feb 10 2020
parent Andre Pany <andre s-e-a-p.de> writes:
On Monday, 10 February 2020 at 19:39:04 UTC, Ernesto Castellotti 
wrote:

 On Monday, 10 February 2020 at 19:00:36 UTC, Andre Pany wrote:

 [...]


 Static libraries are simple collections of object files, there 
 is no difference between linking a static library or several 
 object files

 If you notice when going to compile the executable linka libdl 
 and the static library, then the executable will be linked to 
 dynamic library and will not be a static executable.


Thanks for the explanation.

Kind regards
André
Feb 11 2020