Minimum cmake version for blt about blt HOT 11 CLOSED

Perhaps we should avoid resolving the policy part of this problem within BLT until the cmake_minimum_version is decided. In the meantime, it is easy to add both a minimum version and the cmake policy part to your project's build system.

OK, I'll hold off adding the policy in my PR and leave it as the more portable/flexible MATCHES variant.

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Where would be the most appropriate place to set CMP0057 to NEW. I'd like to include that in my PR (#108).

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Thanks -- I'd think it should be around here -- https://github.com/LLNL/blt/blob/master/SetupBLT.cmake#L63 -- in SetupBLT.cmake.

It should be guarded by the version until we decide about adding a cmake_minimum_version to blt (and which version that should be), since earlier cmake versions will complain about unknown policies.
E.g.

if("${CMAKE_VERSION}" VERSION_GREATER 3.3)
    cmake_policy(SET CMP0057 NEW)
endif()

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I think that it is a feature that is not yet in our blt tests.
It comes up when there is a transitive dependency in the DEPENDS_ON lists.

Perhaps we should avoid resolving the policy part of this problem within BLT until the cmake_minimum_version is decided. In the meantime, it is easy to add both a minimum version and the cmake policy part to your project's build system.

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Thanks @zbeekman.

It looks like we will explicit require cmake-3.3+ for basic blt functionality by testing against ${CMAKE_VERSION} in blt and throwing a FATAL_ERROR for earlier versions.

We will most likely not be adding the cmake_minimum_version to blt since this macro has side effects, and is better left to the user projects that brings in blt.

It is also worth mentioning that some of the CUDA functionality requires a significantly newer version of cmake (e.g. cmake-3.8.x), but since this is an optional feature of blt, we will not make this a requirement for all blt users.

We will be adding documentation and internal checks for these in the near future.

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Let's make it a different PR to keep it separate from the fortran fixes.

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This maybe caused by gmock/gtest overriding the cmake minimum in their code. It is at the top level CMakeLists.txt.

cmake_minimum_required(VERSION 2.6.2)

This should probably be commented out in our code.

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cmake_minimum_required calls were removed and a check was added in BLT to warn if you are below CMake 3.8.

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