rte_eth_dev_count_avail returns different value in library

[Dmitry Kozlyuk]

2022-11-11 13:51 (UTC+0000), Robert Hable:
> Hello Dimitry,
> 
> Yes, I am building DPDK as static library. As far as I have seen it should also be the default option on windows builds?

DPDK builds both static and dynamic libraries by default
("default_library=static" means that DPDK apps will use static libraries).
However, DLLs don't work on Windows currently.

> I tried linking the following libraries to my application, which is using my own dpdk-library, but I had no success in using any dpdk functionality (rte_eth_dev_count_avail() returns 0).
> In the linker output I found out that the libraries are currently unused:
> 
> 1>Unused libraries:
> 1>  C:\Dev\Extern\dpdk\build\lib\librte_eal.a
> 1>  C:\Dev\Extern\dpdk\build\lib\librte_mbuf.a
> 1>  C:\Dev\Extern\dpdk\build\lib\librte_mempool.a
> 1>  C:\Dev\Extern\dpdk\build\lib\librte_ethdev.a

I'm puzzled why these four are unused.
If the DLL using rte_eth_dev_count_avail() links successfully,
the linked must use "librte_ethdev.a".

> 1>  C:\Dev\Extern\dpdk\build\drivers\librte_common_mlx5.a
> 1>  C:\Dev\Extern\dpdk\build\drivers\librte_net_mlx5.a  
> 
> Do you have any other ideas what I am missing there and why they are not linked to it? Is it may be possible to include all the PMD libraries already in my own library, so I only need to link against one library?
> Yes, rte_eth_dev_count_avail() is called directly after rte_eal_init().
> 
> By the way I am using the visual studio 2022 compiler to build my own application and clang for compiling dpdk if that matters.

Please try /WHOLEARCHIVE for these libraries as documented here:

https://learn.microsoft.com/en-us/cpp/build/reference/wholearchive-include-all-library-object-files?view=msvc-160

On Unices, PMDs are also linked using a similar --whole-archive option.
This is needed because there are no direct references from DPDK libraries
to PMDs, because PMDs register themselves at startup.