CODEWITHSUNDEEP
cmake
Constantin
Constantin

Reputation: 17768

Check CMake Cache Variable in Toolchain File

I'm having trouble setting a configuration variable via the command line. I can't determine it from the system, so I expect the user to specify:

cmake -DCMAKE_TOOLCHAIN_FILE=../android.toolchain -DANDROID_ABI:STRING="arm64" ..

Inside my android.toolchain, I have the following:

message(STATUS "Android ABI: ${ANDROID_ABI}")
if( "${ANDROID_ABI}" STREQUAL "" )
   message(FATAL_ERROR "Please specifiy ABI at cmake call -DANDROID_ABI:STRING=armeabi or -DANDROID_ABI:STRING=arm64")
endif()

No matter what, it fails at this line EVEN THOUGH it prints out the correct arm64:

 -- Android ABI: arm64
CMake Error at yaml-cpp/android.toolchain:45 (message):
Please specifiy ABI at cmake call -DANDROID_ABI:STRING=armeabi or -DANDROID_ABI:STRING=arm64

Could anyone direct me to what I'm doing wrong?

I think this has to do with:

Any thoughts or suggestions?

Upvotes: 13

Views: 3694

Answers (3)

上山老人
上山老人

Reputation: 462

I used the CMAKE_TRY_COMPILE_PLATFORM_VARIABLES and it works.

set(CMAKE_SYSTEM_NAME Linux)

set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ANDROID_NDK)

Upvotes: 0

Tsyvarev
Tsyvarev

Reputation: 65928

CMake 3.6 introduces variable CMAKE_TRY_COMPILE_PLATFORM_VARIABLES which contains a list of variables, automatically passed from the main project to the project, created with try_compile.

A toolchain may add its variables to that list, so they could be extracted in a subproject:

message(STATUS "Android ABI: ${ANDROID_ABI}")
if( "${ANDROID_ABI}" STREQUAL "" )
   message(FATAL_ERROR "Please specifiy ABI at cmake call -DANDROID_ABI:STRING=armeabi or -DANDROID_ABI:STRING=arm64")
endif()

# propagate the variable into "inner" subprojects.
list(APPEND CMAKE_TRY_COMPILE_PLATFORM_VARIABLES "ANDROID_ABI")

Caveats:

  1. This approach affects only to source flow of try_compile command. It won't work when try_compile is used for create fully-fledged CMake project with signature

    try_compile(<resultVar> <bindir> <srcdir> <projectName> ...)

    (Approach with setting environment variable, as described in the @sorbet answer, works perfectly in this case.)

  2. This approach won't work for a subproject, created with ExternalProject_Add. (Approach with setting environment variable fails in that case too.)

Upvotes: 1

midrare
midrare

Reputation: 2774

I don't pretend to fully understand what's going on behind the scenes, but here's a workaround that works for me:

# Problem: CMake runs toolchain files multiple times, but can't read cache variables on some runs.
# Workaround: On first run (in which cache variables are always accessible), set an intermediary environment variable.

if (FOO)
    # Environment variables are always preserved.
    set(ENV{_FOO} "${FOO}")
else ()
    set(FOO "$ENV{_FOO}")
endif ()

Upvotes: 10

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