使用C++使用CMake的代码在MacOs上使用clang编译，但在Linux上会引发语法错误。

Question

我需要我的代码同时在Linux和MacOs上工作。

下面是我用来生成Makefile的CMakeLists.txt文件。

cmake_minimum_required(VERSION 3.10)

# set the project name and version
project(PCATests    VERSION 0.1
                                    DESCRIPTION "tests of the framework for building Cellular Automata"
                                    LANGUAGES CXX)

# specify the C++ standard
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)

find_package(OpenMP REQUIRED)

if (${OPENMP_FOUND})
    include_directories(${INCLUDE_DIRS})
endif()

include_directories(../../include ../ext)
link_directories(../../build)

# compile options
if (MSVC)
    # warning level 4 and all warnings as errors
    add_compile_options(/W4 /WX)
    # if the compiler supports OpenMP, use the right flags
    if (${OPENMP_FOUND})
        add_compile_options(${OpenMP_CXX_FLAGS})
    endif()
else()
    # lots of warnings and all warnings as errors
    add_compile_options(-Wall -Wextra -pedantic -Werror)
    if (NOT CMAKE_CXX_COMPILER_ID MATCHES "GNU")
        add_compile_options(-Wno-error=unused-command-line-argument)
    endif()
    # optimizations and debug informations
    add_compile_options(-g -O3)
    # if the compiler supports OpenMP, use the right flags
    if (${OPENMP_FOUND})
        add_compile_options(${OpenMP_CXX_FLAGS})
    endif()

endif()

set(unit_test_targets
    test_sequential_all
    test_operators
    test_library_imports
    test_sequential_automaton
    test_utilities
    test_sequential_leaks_valgrind
    test_omp_automaton
)

foreach(TARGET ${unit_test_targets})
    add_executable(${TARGET} ${TARGET}.cpp)
    target_link_libraries(${TARGET} parallelcellularautomata)
endforeach()

在MacOs上，以下步骤起作用，我得到了最终的可执行文件：

~/repos/parallel-cellular-automata/tests/unit/build$ pwd
/Users/gerardozinno/repos/parallel-cellular-automata/tests/unit/build
~/repos/parallel-cellular-automata/tests/unit/build$ cmake ..
-- The CXX compiler identification is AppleClang 11.0.0.11000033
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenMP_CXX: -Xclang -fopenmp (found version "3.1")
-- Found OpenMP: TRUE (found version "3.1")
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/gerardozinno/repos/parallel-cellular-automata/tests/unit/build
~/repos/parallel-cellular-automata/tests/unit/build$ make
Scanning dependencies of target test_omp_automaton
...
Scanning dependencies of target test_sequential_automaton
[  7%] Building CXX object CMakeFiles/test_sequential_leaks_valgrind.dir/test_sequential_leaks_valgrind.cpp.o
...

[100%] Built target test_sequential_all

在此编译过程之后，我的可执行文件将不会引发警告或错误。

同时，如果我试图在linux Ubuntu上编译相同的代码，使用相同的命令：

gerardo@newton:~/repos/parallel-cellular-automata/tests/unit/build$ pwd
/home/gerardo/repos/parallel-cellular-automata/tests/unit/build
gerardo@newton:~/repos/parallel-cellular-automata/tests/unit/build$ cmake ..
-- The CXX compiler identification is GNU 9.3.0
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenMP_CXX: -fopenmp (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
-- Configuring done
-- Generating done
-- Build files have been written to: /home/gerardo/repos/parallel-cellular-automata/tests/unit/build
gerardo@newton:~/repos/parallel-cellular-automata/tests/unit/build$ make
Scanning dependencies of target test_omp_automaton
[  7%] Building CXX object CMakeFiles/test_omp_automaton.dir/test_omp_automaton.cpp.o

我开始犯像这样的错误。

对于每个For循环，我得到以下错误：

In file included from /home/gerardo/repos/parallel-cellular-automata/tests/unit/../../include/cellular_automata.hpp:6,
                 from /home/gerardo/repos/parallel-cellular-automata/tests/unit/test_omp_automaton.cpp:7:
/home/gerardo/repos/parallel-cellular-automata/tests/unit/../../include/omp_automaton.hpp: In member function ‘virtual void ca::omp::CellularAutomaton<T>::sim
ulate(unsigned int)’:
/home/gerardo/repos/parallel-cellular-automata/tests/unit/../../include/omp_automaton.hpp:93:22: error: expected ‘=’ before ‘{’ token
   93 |         for (size_t i{0}; i < rows; ++i)

在“{”之前表示“=”，下面是我从未遇到过的错误：

/home/gerardo/repos/parallel-cellular-automata/tests/unit/../../include/omp_automaton.hpp:93:9: error: use of local variable with automatic storage from conta
ining function
   93 |         for (size_t i{0}; i < rows; ++i)
      |         ^~~
/home/gerardo/repos/parallel-cellular-automata/tests/unit/../../include/omp_automaton.hpp:93:21: note: ‘size_t i’ declared here
   93 |         for (size_t i{0}; i < rows; ++i)
      |                     ^

说明使用局部变量自动存储从包含函数。

在MacOs上，怎么可能一切都运行得很好，而在linux上，我却出现了错误？我该怎么解决呢？我可以发誓，以前的代码在linux上运行良好，我认为它在包含了

if (NOT CMAKE_CXX_COMPILER_ID MATCHES "GNU")
        add_compile_options(-Wno-error=unused-command-line-argument)
    endif()

在CMakeLists.txt中，但是现在即使我注释了这一行代码也不起作用。

所使用的编译器显示在cmake输出的第一行。

我还在另一台linux机器上尝试了代码，并得到了相同的错误。

Answer 1

正如Tsyvarev在评论中指出的那样，问题是我在Linux上的OpenMp不支持for迭代器的大括号初始化。