Experimental Physics and
Industrial Control System

Michael Davidsaver via Core-talk <core-talk at aps.anl.gov> · Wed, 27 Jan 2021 06:04:56 -0800

On 1/27/21 3:01 AM, Ralph Lange via Core-talk wrote:
> Question about developing on Windows:
> 
> How do you manage unit testing of internal classes in DLLs?
> 
> Internal classes (that are not DLL exported) are by design not visible through the DLL interface, which means linking a unit test against the DLL won't allow it to access the internal APIs it is supposed to test.
> (No such problem on Linux where all functions inside the shared library are visible.)
> 
> I know I can work around by linking the needed objects directly into the test executable. Is there any preferable or better solution?

I'm in the habit of marking these sorts of symbols for export.
In my mind dllexport does not imply a public API.  eg. about half
of the symbols exported by libca.so are only used by libdbCore.so
(for local CA).

On 1/27/21 3:57 AM, Mark Rivers via Core-talk wrote:
...
> That is true by default, but GCC >= 4 has __attribute__ ((visibility ("hidden"))) which will also hide classes on Linux.
> 
> This article makes the argument for why it is a good idea to use it:
> 
> https://gcc.gnu.org/wiki/Visibility

I keep the following in configure/CONFIG_SITE.local

USR_CFLAGS_Linux += -fvisibility=hidden
USR_CXXFLAGS_Linux += -fvisibility=hidden -fvisibility-inlines-hidden

Mostly this helps me find dllimport/export problems earlier, though
there is also some slight reduction in linking/loading time.
(I'll take what I can get wrt. c++ build times)

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System