unused-command-line-argument warning with Apple Clang

[StrikerRUS]

There is a warning

clang: warning: argument unused during compilation: '-pthread' [-Wunused-command-line-argument]

in the current master branch.

I've done binsearching among available Xcode versions on Azure Pipelines and found that the lowest Xcode version which recognizes -pthread and doesn't produce the warning is 9.3.

ping @guolinke and @chivee

[guolinke]

@StrikerRUS refer to https://stackoverflow.com/questions/2391194/what-is-gs-pthread-equiv-in-clang/19382746#19382746

[chivee]

maybe just adding -Qunused-arguments option for those under 9.3

[StrikerRUS]

@chivee Won't this hide from us future (possibly dangerous) warnings?

I've tried the following solution, but unfortunately warning hasn't gone.

if((CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang") AND (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.1.0"))
    if("${CMAKE_SHARED_LINKER_FLAGS}" STREQUAL "")
        string(REPLACE "-pthread" "" OLD_APPLE_CLANG_SHARED_LINKER_FLAGS "${CMAKE_CXX_FLAGS}")
    else()
        string(REPLACE "-pthread" "" OLD_APPLE_CLANG_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
    endif()
    set(CMAKE_SHARED_LINKER_FLAGS "${OLD_APPLE_CLANG_SHARED_LINKER_FLAGS}" CACHE STRING "" FORCE)
    if("${CMAKE_EXE_LINKER_FLAGS}" STREQUAL "")
        string(REPLACE "-pthread" "" OLD_APPLE_CLANG_EXE_LINKER_FLAGS "${CMAKE_CXX_FLAGS}")
    else()
        string(REPLACE "-pthread" "" OLD_APPLE_CLANG_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
    endif()
    set(CMAKE_EXE_LINKER_FLAGS "${OLD_APPLE_CLANG_EXE_LINKER_FLAGS}" CACHE STRING "" FORCE)
endif()

[guolinke]

@StrikerRUS
from https://stackoverflow.com/questions/2391194/what-is-gs-pthread-equiv-in-clang/19382746#19382746
I think the pthread is needed for compiling, but not for linking.
can we set this in cmake ?

[StrikerRUS]

@guolinke I've tried: #1805 (comment). Unfortunately, without any luck 😢 .

[StrikerRUS]

Closed in favor of being in #2302. We decided to keep all feature requests in one place.

Welcome to contribute this feature! Please re-open this issue (or post a comment if you are not a topic starter) if you are actively working on implementing this feature.

[StrikerRUS]

I've done binsearching among available Xcode versions on Azure Pipelines and found that the lowest Xcode version which recognizes -pthread and doesn't produce the warning is 9.3.

According to the

• the lowest Xcode version which recognizes -pthread and doesn't produce the warning is 9.3;

• we have no easy access to Xcode versions less than 10.3 (macOS-10.14 Azure Pipelines environment is deprecated #4797);
• this is just warning, not error

I'm closing this issue.