如何解决当包含<iostream>时，在CYGWIN下与GCC的交叉编译失败
我已使用https://preshing.com/20141119/how-to-build-a-gcc-cross-compiler/上的文章作为源，在CYGWIN环境下为Linux构建了跨工具链。
编译和安装成功完成。
使用的组件是：
- binutils-2.35
- cloog-0.18.1
- gcc-10.2.0
- glibc-2.32
- gmp-6.1.2
- isl-0.20
- linux-5.9.3
- mpc-1.1.0
- mpfr-4.0.2
GCC配置为：
$ x86_64-unknown-linux-gnu-g++ --verbose
Using built-in specs.
COLLECT_GCC=x86_64-unknown-linux-gnu-g++
COLLECT_LTO_WRAPPER=/opt/cross/x86_64-unknown-linux-gnu/libexec/gcc/x86_64-unknown-linux-
gnu/10.2.0/lto-wrapper.exe
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-10.2.0/configure --prefix=/opt/cross/x86_64-unknown-linux-gnu --
target=x86_64-unknown-linux-gnu --enable-languages=c,c++ --disable-nls --disable-multilib --with-
headers=/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/linux
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.2.0 (GCC)
但是当我尝试编译包含其中的简单Hello World应用程序时，我遇到了许多不同的错误：
$ x86_64-unknown-linux-gnu-g++ main.cpp
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h:35,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr.h:148,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/atomicity.h:35,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/ios_base.h:39,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ios:42,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ostream:38,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/iostream:39,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:240:34: error: 'clockid_t' has not been declared
240 | clockid_t __clockid,| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:375:12: error: 'cpu_set_t' does not name a type
375 | const cpu_set_t *__cpuset)
| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:382:6: error: 'cpu_set_t' has not been declared
382 | cpu_set_t *__cpuset)
| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:466:14: error: 'cpu_set_t' does not name a type
466 | const cpu_set_t *__cpuset)
| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:471:8: error: 'cpu_set_t' has not been declared
471 | cpu_set_t *__cpuset)
| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:765:9: error: 'clockid_t' has not been declared
765 | clockid_t __clockid,| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:911:12: error: 'clockid_t' has not been declared
911 | clockid_t __clockid,| ^~~~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:933:12: error: 'clockid_t' has not been declared
933 | clockid_t __clockid,| ^~~~~~~~~
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr.h:148,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h:114:1: error: 'sched_yield' was not declared in this scope; did you mean 'pthread_yield'?
114 | __gthrw(sched_yield)
| ^~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h:114:1: error: 'sched_yield' was not declared in this scope; did you mean 'pthread_yield'?
114 | __gthrw(sched_yield)
| ^~~~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h: In function 'int __gthread_yield()':
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h:693:33: error: '__gthrw_sched_yield' cannot be used as a function
693 | return __gthrw_(sched_yield) ();
| ^
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/sys/select.h:37,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/sys/types.h:179,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/stdlib.h:394,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/cstdlib:75,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:41,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/basic_string.h:6535,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/string:55,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/locale_classes.h:40,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/ios_base.h:41,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/bits/types/struct_timeval.h: At global scope:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/bits/types/struct_timeval.h:8:8: error: redefinition of 'struct timeval'
8 | struct timeval
| ^~~~~~~
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/pthread.h:23,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/gthr-default.h:35,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/sys-include/time.h:16:8: note: previous definition of 'struct timeval'
16 | struct timeval {
| ^~~~~~~
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:44,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h: In constructor '__gnu_cxx::__stoa(_TRet (*)(const _CharT*,_CharT**,_Base ...),const char*,const _CharT*,std::size_t*,_Base ...)::_Save_errno::_Save_errno()':
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:63:27: error: 'errno' was not declared in this scope
63 | _Save_errno() : _M_errno(errno) { errno = 0; }
| ^~~~~
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/basic_string.h:6535,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:45:1: note: 'errno' is defined in header '<cerrno>'; did you forget to '#include <cerrno>'?
44 | #include <cerrno>
+++ |+#include <cerrno>
45 |
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:44,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h: In destructor '__gnu_cxx::__stoa(_TRet (*)(const _CharT*,_Base ...)::_Save_errno::~_Save_errno()':
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:64:23: error: 'errno' was not declared in this scope
64 | ~_Save_errno() { if (errno == 0) errno = _M_errno; }
| ^~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:64:23: note: 'errno' is defined in header '<cerrno>'; did you forget to '#include <cerrno>'?
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h: In function '_Ret __gnu_cxx::__stoa(_TRet (*)(const _CharT*,_Base ...)':
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:84:16: error: 'errno' was not declared in this scope
84 | else if (errno == ERANGE
| ^~~~~
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:84:16: note: 'errno' is defined in header '<cerrno>'; did you forget to '#include <cerrno>'?
In file included from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/system_error:39,from /opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/bits/ios_base.h:46,from main.cpp:1:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/error_constants.h: At global scope:
/opt/cross/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/include/c++/10.2.0/x86_64-unknown-linux-gnu/bits/error_constants.h:122:27: error: 'ENOTSUP' was not declared in this scope
122 | not_supported = ENOTSUP,|
UPD：就我而言，WSL和虚拟机不是可选项
解决方法
我设法解决了这个问题。
问题出在sys-include目录中opt/cross/x86_64-unknown-linux-gnu/sys-include
此目录包含的文件名称与
中的文件相同
opt/cross/x86_64-unknown-linux-gnu/include
但内容不同。
编译器在常规sys-include之前搜索include目录。
重命名或删除sys-include解决了该问题，并且可以编译代码。
我不知道sys-include目录的用途，创建时间以及为什么该目录中的重复文件包含其他内容。
接受我自己的帖子作为回答，表明该问题可以解决。
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