FindThreads 仅在启用 C 或 CXX 语言时有效

Question

我正在尝试构建一个可移植的 gcc，以允许其他人使用不同的系统进行编译。

我使用 crosstool-ng 为 x86_64 交叉编译 gcc-8.2，我构建了一个静态工具链。

我创建了以下工具链文件：

#set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
set(CMAKE_SYSTEM_PROCESSOR "x86_64")
set(QAMF_ROOT "/opt/hyperserver-dev/x86_64-qamf")

set(COMPILER_ROOT "${QAMF_ROOT}")
set(COMPILER_PREFIX "x86_64-qamf-linux-gnu-")
set(C_COMPILER "gcc")
set(CXX_COMPILER "g++")

# specify the cross compile
set(CMAKE_C_COMPILER    ${COMPILER_ROOT}/bin/${COMPILER_PREFIX}${C_COMPILER} )
set(CMAKE_CXX_COMPILER  ${COMPILER_ROOT}/bin/${COMPILER_PREFIX}${CXX_COMPILER} )

# HyperServer sysroot path
set(HYPERSERVER_SYSROOT "${COMPILER_ROOT}/x86_64-qamf-linux-gnu/sysroot") 

# where is the target environment 
set(CMAKE_FIND_ROOT_PATH ${HYPERSERVER_SYSROOT} )

# search for programs in the build host directories
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

# for libraries and headers in the target directories
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

在我的主机上它运行良好，我可以毫无问题地进行编译，但是当我将工具链文件移动到另一台机器上时，我遇到了问题。如果我尝试在我的 cmake 中包含线程，则会出现以下错误：

CMake Error at /usr/local/share/cmake-3.13/Modules/FindThreads.cmake:54 (message):
  FindThreads only works if either C or CXX language is enabled
Call Stack (most recent call first):
  CMakeLists.txt:2 (find_package)


-- Configuring incomplete, errors occurred!
make: *** No targets specified and no makefile found.  Stop.

这是我的CMakeFiles/txt

cmake_minimum_required(VERSION 3.9)
find_package(Threads REQUIRED)
project(HelloWorld C CXX)
add_executable(${PROJECT_NAME} "main.cpp")
target_link_libraries(${PROJECT_NAME} PRIVATE Threads::Threads)

Answer 1

地点

find_package(Threads REQUIRED)

之后

project(HelloWorld C CXX)

这是错误消息的内容：project() 调用启用了语言，因此找到线程会成功。

通常，所有 find_package 调用应该在 project() 一个之后。

FindThreads 仅在启用 C 或 CXX 语言时有效

FindThreads only works if either C or CXX language is enabled

c++

cmake

toolchain