使用llvm-11与gcc-11用-std=c++2a编译的标准库标头时出错

Question

我试图与gcc标准库标题一起使用clang，如下所示：

/opt/rh/llvm-toolset-11.0/root/usr/bin/clang -MD -MF bazel-out/k8-fastbuild/bin/external/com_google_googletest/_objs/gtest/gtest-typed-test.d '-frandom-seed=bazel-out/k8-fastbuild/bin/external/com_google_googletest/_objs/gtest/gtest-typed-test.o' -iquote external/com_google_googletest -iquote bazel-out/k8-fastbuild/bin/external/com_google_googletest -isystem external/com_google_googletest/googlemock -isystem bazel-out/k8-fastbuild/bin/external/com_google_googletest/googlemock -isystem external/com_google_googletest/googlemock/include -isystem bazel-out/k8-fastbuild/bin/external/com_google_googletest/googlemock/include -isystem external/com_google_googletest/googletest -isystem bazel-out/k8-fastbuild/bin/external/com_google_googletest/googletest -isystem external/com_google_googletest/googletest/include -isystem bazel-out/k8-fastbuild/bin/external/com_google_googletest/googletest/include -isystem /opt/rh/devtoolset-11/root/usr/include/c++/11 -isystem /opt/rh/devtoolset-11/root/usr/include/c++/11/bits -isystem /opt/rh/devtoolset-11/root/include/c++/11/x86_64-redhat-linux/bits -fdiagnostics-color -Wfatal-errors '-std=c++2a' -Wall -Wno-sign-compare '--gcc-toolchain=/opt/rh/devtoolset-11/root' -Wheader-guard -pthread -c external/com_google_googletest/googletest/src/gtest-typed-test.cc -o bazel-out/k8-fastbuild/bin/external/com_google_googletest/_objs/gtest/gtest-typed-test.o

然后我得到了这个错误：

In file included from external/com_google_googletest/googletest/include/gtest/gtest.h:62:
In file included from external/com_google_googletest/googletest/include/gtest/internal/gtest-internal.h:40:
In file included from external/com_google_googletest/googletest/include/gtest/internal/gtest-port.h:395:
/opt/rh/devtoolset-11/root/usr/include/c++/11/bits/regex.h:56:9: fatal error: use of undeclared identifier 'regex_constants'
                      regex_constants::match_flag_type     __flags);

错误的原因是什么？gcc和克朗之间有不相容的地方吗？我应该安装clang和libc++吗?这是通过安装llvm软件包来实现的吗？

Answer 1

gtest-port.h文件包含一个带有#include <regex.h>的文件(有关代码，请参见这里 )。它期望文件是POSIX regex.h，它通常直接安装在前缀/usr/include下。正如您在错误消息中看到的那样，编译器尝试包含错误的/usr/include/c++/11/bits/regex.h文件。

.../bits/中的头文件不打算由用户代码直接包含。是标准库实现的内部。因此，直接包含它失败(丢失的符号可能在另一个内部头文件中定义)对我来说并不奇怪。

为了解决您的问题，我建议您尝试在编译命令中省略.../bits目录。我不知道是谁告诉您包含它们的，但是它们不应该添加到编译器搜索路径中。

*将这两个标志从编译器命令行中删除：

-isystem /opt/rh/devtoolset-11/root/usr/include/c++/11/bits
-isystem /opt/rh/devtoolset-11/root/include/c++/11/x86_64-redhat-linux/bits