[CMake] [cmake-developers] Debugging find_package() search behavior?

[David Cole]

Is there a ZLIBConfig.cmake file which find_package is searching for?
(i.e. -- somewhere under that directory does that file exist?) On
Windows the case won't matter, but on Linux, a find_package(ZLIB will
expect a case-sensitive match on a ZLIBConfig.cmake file.

If ZLIBConfig.cmake exists, it needs to exist in one of the locations
on that find_package documentation snippet you sent. If it's not
directly in the "zlib" folder, or one of the other folders listed,
then it won't be found. The directory it is in, or something matching
one of those in the list needs to be included in your
CMAKE_PREFIX_PATH.


If that file does not exist, then the CMake FindZLIB.cmake module will
be used in an attempt to find your zlib... And the help for that
speaks of setting a ZLIB_ROOT var if you want to direct it to find a
given zlib. See the "HINTS" section here:

    https://cmake.org/cmake/help/v3.6/module/FindZLIB.html#hints


One more hint regarding CMAKE_PREFIX_PATH : despite its name, it is a
**list** of paths, and you can use multiple semi-colon separated
values if necessary. So, if appending "/zlib" works, then you could
always find zlib and all your other stuff too by using two directories
as your CMAKE_PREFIX_PATH value.


HTH,
David C.



On Tue, Aug 29, 2017 at 11:11 AM, Robert Dailey
<rcdailey.lists at gmail.com> wrote:
> What I'm hoping for is that find_package() follows the rules it
> documents here:
> https://cmake.org/cmake/help/v3.6/command/find_package.html
>
> Specifically, it states it searches these paths (and that <name> is
> treated case-insensitive):
>
> <prefix>/                                               (W)
> <prefix>/(cmake|CMake)/                                 (W)
> <prefix>/<name>*/                                       (W)
> <prefix>/<name>*/(cmake|CMake)/                         (W)
> <prefix>/(lib/<arch>|lib|share)/cmake/<name>*/          (U)
> <prefix>/(lib/<arch>|lib|share)/<name>*/                (U)
> <prefix>/(lib/<arch>|lib|share)/<name>*/(cmake|CMake)/  (U)
>
> If this is true, then the 3rd one from the top should be a match,
> because <prefix> is set to:
>
> E:/code/frontend/msvc_2015/third_party/installed
>
> And <name> is set to ZLIB in find_package() first argument, so it
> should be adding that to the end.
>
> I need to keep CMAKE_PREFIX_PATH pointing to the parent directory
> ("installed") because I have other libraries that get installed in
> that directory, each with their own directory to contain their
> installation files. If find_package() is appending <name> to <prefix>
> like it says it should, it should find each one of them without
> switching the value of CMAKE_PREFIX_PATH.
>
> Am I misunderstanding something?
>
>
> On Tue, Aug 29, 2017 at 10:06 AM, David Cole <DLRdave at aol.com> wrote:
>> Shouldn't the "/zlib" at the end be included in your CMAKE_PREFIX_PATH?
>>
>> On Tue, Aug 29, 2017 at 11:01 AM, Robert Dailey
>> <rcdailey.lists at gmail.com> wrote:
>>> On Tue, Aug 29, 2017 at 9:56 AM, Brad King <brad.king at kitware.com> wrote:
>>>> On 08/29/2017 10:55 AM, Brad King wrote:
>>>>> On 08/29/2017 10:48 AM, Robert Dailey wrote:
>>>>>> CMAKE_PREFIX_PATH: E:/code/frontend/msvc_2015/third_party/installed
>>>>>> CMAKE_FIND_ROOT_PATH: E:/code/frontend/msvc_2015/third_party/installed
>>>>>
>>>>> I'm not sure how CMAKE_FIND_ROOT_PATH's path re-rooting interacts with
>>>>> drive letters on Windows.
>>>>
>>>> Oops, sent too soon.
>>>>
>>>> CMAKE_FIND_ROOT_PATH should not be necessary here.  It's for cross-compiling
>>>> to re-root paths like `/usr` into some prefix on the host.
>>>>
>>>> -Brad
>>>
>>> Ok but even if I remove that, find_package() still isn't working......
>>> --
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