[CMake] cmake 2.6 and find_library with MinGW generator

[Christian Ehrlicher]

Bill Hoffman schrieb:
> Christian Ehrlicher wrote:
> 
>>>
>> I understood the warning - I know that it is not mandatory. 
>  > But how useful is a warning when the only way to get rid of them is
>  >
>> to disable it? I either have to fix all places (including the system libs
>  >) or disable it and don't care at all. That's stupid.
>>
> 
> OK, so you don't understand the warning.  Not your fault it is just hard 
> to write as many others do not understand it.
> 
> Here is the problem:
> 
> We changed from -L/path/to -lA  to /path/to/library.  In some rare cases 
> projects have something like this:
> 
> target_link_libraries(foo /path/to/libA.a B)
> 
> And B is actually in /path/to/libB.a
> 
> We have no easy way of telling the difference between the above and
> 
> target_link_libraries(foo /path/to/libA.a somesystemlib)
> 
> Where somesystemlib library can be found by the compiler.
> 
> So, we had two choices for 2.6:
> 
> 1. Always add -L/path if there is at least one non-full path library 
> linked in.  This makes extra long link lines.
> 
> 2. Do not add -L/path and give no warning - we will break some projects 
> with no warning, and the break will happen with a linker error during 
> the build step.
> 
> So, what we did was do 1 by default, but give a warning.
> 
> So, to make a long story short, setting the policy to NEW is not 
> "disabling" the warning, it is asking CMake to link libraries in the new 
> better 2.6 way.  So, the correct fix is to set the policy to NEW, and if 
> your stuff links then the warning was in error. If a project has 2.6 as 
> the minimum require version there is no warning and things are always 
> linked full path.
> 
Thx for the explanation.


Christian

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