[cmake-developers] PATHS guess in find_package ignored with NO_DEFAULT_PATH & CMAKE_FIND_ROOT_PATH_MODE_PACKAGE

[Julien Schueller]

> De: "Nils Gladitz" <nilsgladitz at gmail.com>
> À: "Julien Schueller" <schueller at phimeca.com>, "cmake-developers"
> <cmake-developers at cmake.org>
> Envoyé: Vendredi 1 Juillet 2016 13:57:40
> Objet: Re: [cmake-developers] PATHS guess in find_package ignored with
> NO_DEFAULT_PATH & CMAKE_FIND_ROOT_PATH_MODE_PACKAGE

> On 07/01/2016 01:44 PM, Julien Schueller wrote:

>>> De: "Nils Gladitz" <nilsgladitz at gmail.com>
>>> À: "Julien Schueller" <schueller at phimeca.com> , "cmake-developers"
>>> <cmake-developers at cmake.org>
>>> Envoyé: Vendredi 1 Juillet 2016 12:37:47
>>> Objet: Re: [cmake-developers] PATHS guess in find_package ignored with
>>> NO_DEFAULT_PATH & CMAKE_FIND_ROOT_PATH_MODE_PACKAGE

>>> On 07/01/2016 11:13 AM, Julien Schueller wrote:

>>>> I'm using find_package in no-module mode with the PATHS option to provide a
>>>> hard-coded guess to a path where a sublibrary 'hmat' was previously found,
>>>> and with the NO_DEFAULT_PATH to not find it first in system directories.
>>>> find_package (HMAT REQUIRED NO_MODULE PATHS <hmat-prefix>/lib/cmake/hmat
>>>> NO_DEFAULT_PATH)

>>>> So far so good. Now I want to cross-compile with the usual toolchain file:
>>>> set (CMAKE_FIND_ROOT_PATH /usr/i686-w64-mingw32)
>>>> set (CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
>>>> set (CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
>>>> set (CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
>>>> ...
>>>> This works wonderfully too.

>>>> But now I add CMAKE_FIND_ROOT_PATH_MODE_PACKAGE to ONLY in my toolchain file to
>>>> prevent detecting native libraries
>>>> set (CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
>>>> And now find_package fails to find my package!

>>>> I'm puzzled as I did not find in the doc something that explains why the PATHS
>>>> is ignored (step #8 in find_package):
>>>> https://cmake.org/cmake/help/v3.5/command/find_package.html#command:find_package

>>> The given path "<hmat-prefix>/lib/cmake/hmat" is prefixed by the paths in
>>> CMAKE_FIND_ROOT_PATH.
>>> Which means that (given ONLY) cmake only looks for the package in
>>> "/usr/i686-w64-mingw32/<hmat-prefix>/lib/cmake/hmat".

>>> You might want to e.g. add <hmat-prefix> to CMAKE_FIND_ROOT_PATH and use PATHS /
>>> instead.

>>> Nils

>> Thanks,

>> In my case <hmat-prefix> has the same value as CMAKE_FIND_ROOT_PATH, and even if
>> I modify the PATHS option value to be relative (PATHS lib/cmake/hmat) the
>> detection fails.
>> (They're not actually set to /usr/i686-w64-mingw32 but some absolute location in
>> my home where I unzip a mingw toolchain, but I can reproduce the issue on
>> another box where the toolchain is natively /usr/i686-w64-mingw32).

> I don't think behavior for relative paths is defined.

> Use absolute paths like "/lib/cmake/hmat", just "/" probably works as well
> (since the path in the prefix matches
> "<prefix>/(lib/<arch>|lib|share)/cmake/<name>*/").

> Nils

Yes, if I use just "/lib/cmake/hmat" it works. Couldn't cmake see that that my absolute path begins with CMAKE_FIND_ROOT_PATH and hence should be treated as valid according to CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ? 

-- 
Julien Schueller 
Phimeca Engineering 
www.phimeca.com 
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