Fix option --libs output library path

[JackBoosY]

The dep does not consider the cmake generator expression and the absolute path.
We may meet some different situation:

1. dep was already handled like -pthread:
   dep_name should be ${dep}.
2. dep is system library like dl / m:
   dep_name should be -l${dep}
3. dep is $<$<CONFIG:DEBUG>:LIB_PATH> or $<$<NOT:$<CONFIG:DEBUG>>:LIB_PATH> that from LIB-config.cmake:
   dep_name should be ${LIB_PATH}.
4. dep is an absolute path like /usr/home/lib.a or /usr/home/lib.so etc:
   dep_name should be ${dep}.

Related: microsoft/vcpkg#18580

[vadz]

@MaartenBent could you please review this? TIA!

[MaartenBent]

This breaks determining the external libraries, see my inline comments.

[MaartenBent]

Why did you remove get_filename_component(dep_name ${dep} NAME)? We need this to get the library name.
With this change it will be /Applications/Xcode.app/Contents/..../MacOSX11.3.sdk/usr/lib/libz.tbd instead of -lz, or /usr/lib/x86_64-linux-gnu/libX11.so instead of -lX11.

[JackBoosY]

For some port use *Config.cmake or *-config.cmake, the INTERFACE_LINK_LIBRARIES may contains cmake generator expression like $<$<NOT:$<CONFIG:DEBUG>>:LIB_PATH>.
If we use get_filename_component(dep_name ${dep} NAME), the value of dep_name is NAME>.

[MaartenBent]

But can you use the regex to extract the library from the generator expression, and then use get_filename_component on this?

[JackBoosY]

I don't know why you use the file name directly here.
If the dependency library is not in system like /usr/lib, the compiler will fail to search this library.

[MaartenBent]

I try to generate the same output as configure does when generating wx-config. and it only has the library names.
If it is in a different path, maybe we have to specify -Lpath/to/lib before the library. Or require the user to have it in PATH.

[JackBoosY]

Yes, we must choose one way to solve this issue.

[talregev]

@JackBoosY @MaartenBent Any news?

[MaartenBent]

I can't really work on this, since on the build systems I can test this on (Windows MSVC & MinGW, Ubuntu, macOS) I do not get paths with generator expressions.
Maybe you can give a few examples of such paths?

What about the following solution?
If dep contains a generator expression, we extract both the path and library name. In pseudo code:

if (dep contains generator expression)
    dep_path = regex to extract path
    dep_name = regex to extract name
else()
    get_filename_component(dep_name ${dep} NAME)
endif()

And before adding the library name, we add the library path:

if (dep_path)
    wx_string_append(${var} "-L${dep_path} ")
endif()
if(dep_name STREQUAL "libc.so")
...

This should hopefully fix your problem. Some other additions, but probably not needed immediately, is keeping track of the added dep_path so they are added only once. And maybe extracting the path in the no-generator-expression case too.

[Be-ing]

Thanks for working on this. I hope this gets resolved soon so we can use vcpkg for Tenacity.

[talregev]

Also for our side can get resolve:
use vcpkg in our linux manager
BOINC/boinc#4385

[MaartenBent]

After rethinking this, I suppose it could be merged as it is now.
It will still have some libraries with full path and extension even when it is not required (like I mentioned earlier #2402 (comment)), but I suppose it is more important to keep the path in case it is not in a default location.

And if needed, we could add something in the future that strips default locations like /usr/lib or the macOS sdk location.

[vadz]

Thanks for the changes and for the review, merging it now with just a minor fix for a typo in a comment.