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

[David Cole]

That's correct:

find modules do what they want, and most do not pay attention to
CMAKE_PREFIX_PATH.

It's better to use a config file, but when you have to use a find
module, you have to dig in and figure out the right way to use each
one.



On Tue, Aug 29, 2017 at 11:25 AM, Robert Dailey
<rcdailey.lists at gmail.com> wrote:
> I think the discrepancy here might be config vs module find mode. The
> documentation I linked seems to be for config mode only, however I'm
> utilizing the CMake-shipped FindZLIB.cmake module to find this
> particular library. Does this offer no guarantees on how
> CMAKE_PREFIX_PATH is used?
>
> On Tue, Aug 29, 2017 at 10:11 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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