redis++_static should link to hiredis_static

[msardonini]

Hi, thanks for the project I've been finding it very useful!

This pull request is fairly simple, it allows the redis++_static target to link to the hiredis_static target instead of the current hiredis target.

My project uses the static version of redis++ because it's intended to be deployed on embedded devices, and having as many dependencies included in the libredis++.a library makes configuration management much easier. Because libredis++.a currently links to libhiredis.so, I need to make sure that all deployment devices also receive the exact version of libhiredis.so, a problem is made a little more difficult because the hiredis can't be built in the same project, redis++ expects to find hiredis installed at the system level. (This PR for reference)

The proposed PR introduces the cmake variable REDIS_PLUS_PLUS_HIREDIS_LIBS_STATIC, which is constructed from REDIS_PLUS_PLUS_HIREDIS_LIBS, but appends _static where necessary. I have tested on version with and without SSL.

Let me know if you have any questions, or if other edits are necessary.

Thanks

[sewenew]

Thanks for your contribution!

I did some research, and found that hiredis' static target was added recently. Before that, even the latest stable release of hiredis-v1.0.2, does not supporthiredis::hiredis_static. So when running cmake for redis-plus-plus with an older version hiredis, cmake can not find hiredis::hiredis_static target, and fails.

In short, this PR breaks legacy code...

In order to solve the problem, we need to check if hiredis::hiredis_static exists, if it does not exist, link to hiredis::hiredis instead.

B.T.W. I also use redis-plus-plus and hiredis with static libs. Although cmake links redis-plus-plus with dynamic lib of hiredis, I can still link my application to both redis-plus-plus and hiredis' static libs.

c++ -std=c++17 -I/path/to/include -o app app.cpp /path/to/libredis++.a /path/to/libhiredis.a -pthread

Not sure why it cannot work with you. Maybe you can share some ideas :)

Regards

[msardonini]

Hi @sewenew,

Thanks for your research and thoughts!

Good point that the hiredis::hiredis_static cmake target is new. I probably should have added that check regardless. Luckily, cmake makes this pretty easy, I've added some checks that make sure that the hiredis::hiredis_static cmake target is defined before trying to link to it. Otherwise it will use the same behavior as before.

I have tested this branch with hiredis version v1.0.2 and v0.14.2, both work as expected with the new cmake change.

Let me know if you have any more questions/concerns,

Thanks,

[sewenew]

@msardonini Thanks a lot for your contribution!

Regards