为 riscv64-unknown-elf-g++ 编译 cmake 时如何出错

Question

当我从终端 cmake .. 时，错误如下所示：

(base) k:~ cd /Users/yuli/Documents/version3/cpp/
(base) k:~ ls
CMakeLists.txt      src
riscv-gnu-toolchain test
(base) k:~ mkdir build
(base) k:~ cd build
(base) k:~ cmake ..
-- The C compiler identification is AppleClang 11.0.3.11030032
-- The CXX compiler identification is AppleClang 11.0.3.11030032
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
RegularExpression::compile(): Nested *?+.
RegularExpression::compile(): Error in compile.
CMake Error at CMakeLists.txt:10 (if):
  if given arguments:

    "/Library/Developer/CommandLineTools/usr/bin/c++" "MATCHES" ".*riscv64-unknown-elf-g++"

  Regular expression ".*riscv64-unknown-elf-g++" cannot compile


-- Configuring incomplete, errors occurred!
See also "/Users/yuli/Documents/version3/cpp/build/CMakeFiles/CMakeOutput.log".

我尝试了“STREQUAL”而不是 MATCHES，但没有奏效。知道这里可能出了什么问题吗？

CMakeLists.txt 如下：

cmake_minimum_required(VERSION 3.13)
project(ofdmchain)

set(CMAKE_CXX_FLAGS "-std=c++14")

add_definitions(-DCOMPILES_ON_PC -Wall -Wextra)

configure_file(${CMAKE_SOURCE_DIR}/src/config.hpp.in ${CMAKE_BINARY_DIR}/config.hpp)

if("${CMAKE_CXX_COMPILER}" MATCHES ".*riscv64-unknown-elf-g++")
  message(STATUS "Compiling RISCV")
  SET(RISCV 1)
else()
  message(STATUS "Compiling X86")
  SET(RISCV 0)
endif()

add_library(ofdm
  src/transmitter.cpp
  src/configuration.cpp

  src/ofdm.hpp
  src/datatypes.hpp
  )
target_include_directories(ofdm PRIVATE ${CMAKE_SOURCE_DIR}/../reference_matlab)
target_include_directories(ofdm PRIVATE ${CMAKE_SOURCE_DIR}/src/)

if (NOT ${RISCV})
  add_executable(unit_tests
    test/catch_main.cpp
    test/test_sanity.cpp
    test/test_utilities.cpp
    test/test_transmitter.cpp
    )
  target_include_directories(unit_tests PUBLIC ${CMAKE_CURRENT_BINARY_DIR})
  target_include_directories(unit_tests PUBLIC ${CMAKE_SOURCE_DIR}/src)
  target_link_libraries(unit_tests ofdm)
endif()

我还尝试在 g++ 退出的地方以及 - where - 存在的地方添加 ++。并且也厌倦了“STREQUAL”而不是“MATCHES”，它也不起作用。可能是PATH中c++的问题？

Answer 1

CMake“内部错误”

RegularExpression::compile(): Nested *?+.

大约是最后两个+ 字符：在正则表达式中，这些字符具有特殊含义。

使+ 字符（和其他特殊字符）被处理字面意思的方法：

1. 转义使用\ 的字符。注意，转义字符本身应该在CMake字符串中转义，所以你需要写它两次：

   if("${CMAKE_CXX_COMPILER}" MATCHES ".*riscv64-unknown-elf-g\\+\\+")
   

2. 将字符放入方括号 ([])。在[] 内部，所有特殊字符都失去了它们的特殊含义：

   if("${CMAKE_CXX_COMPILER}" MATCHES ".*riscv64-unknown-elf-g[+][+]")
   

---

还要注意，在某些if 条件下，不需要显式取消引用该变量：CMake 自己会这样做。

所以，可以写

if(CMAKE_CXX_COMPILER MATCHES ".*riscv64-unknown-elf-g[+][+]")

在documentationif 命令中查看更多信息。