我使用Crosstool-ng构建了一个gcc工具链，但生成的g ++不会编译和/或链接C ++ 11异常。
如果我尝试编译：
#include <exception>
int main()
{
std::current_exception();
}
通过：
arm-none-linux-gnueabihf-g++ -std=c++11 foo.cpp
我明白了：
foo.cpp: In function 'int main()':
foo.cpp:5:9: error: 'current_exception' is not a member of 'std'
std::current_exception();
^~~
然而，如果我另外提供cortex-a9作为cpu，那么haviour会改变：
arm-none-linux-gnueabihf-g++ -mcpu=cortex-a9 -std=c++11 foo.cpp
结果：
/tmp/cc13AEjE.o: In function `main':
foo.cpp:(.text+0x14): undefined reference to `std::current_exception()'
foo.cpp:(.text+0x20): undefined reference to
`std::__exception_ptr::exception_ptr::~exception_ptr()'
collect2: error: ld returned 1 exit status
我在工具链中为current_exception加油，这对我来说似乎很好：
grep -r -e current_exception arm-none-linux-gnueabihf/
Binary file arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/sysroot/lib/libstdc++.so.6.0.22 matches
Binary file arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/sysroot/lib/libstdc++.a matches
Binary file arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/sysroot/lib/libsupc++.a matches
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/cxxabi.h: __cxa_current_exception_type() _GLIBCXX_NOTHROW __attribute__ ((__pure__));
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/future: (*_M_result)->_M_error = current_exception();
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/future: (*_M_result)->_M_error = current_exception();
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/bits/exception_ptr.h: exception_ptr current_exception() _GLIBCXX_USE_NOEXCEPT;
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/bits/exception_ptr.h: friend exception_ptr std::current_exception() _GLIBCXX_USE_NOEXCEPT;
arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/include/c++/6.3.0/bits/exception_ptr.h: return current_exception();
arm-none-linux-gnueabihf/arm-none-linux- gnueabihf/include/c++/6.3.0/bits/nested_exception.h: nested_exception() noexcept : _M_ptr(current_exception()) { }
我用于Crosstool-ng的设置是：
arm-none-linux-gnueabihf/bin/arm-none-linux-gnueabihf-g++ -v
Using built-in specs.
COLLECT_GCC=x-tools/arm-none-linux-gnueabihf/bin/arm-none-linux-gnueabihf-g++
COLLECT_LTO_WRAPPER=/home/builduser/x-tools/arm-none-linux-gnueabihf/libexec/gcc/arm-none-linux-gnueabihf/6.3.0/lto-wrapper
Target: arm-none-linux-gnueabihf
Configured with: /home/builduser/build/.build/src/gcc-6.3.0/configure
--build=x86_64-build_pc-linux-gnu
--host=x86_64-build_pc-linux-gnu
--target=arm-none-linux-gnueabihf
--prefix=/home/builduser/x-tools/arm-none-linux-gnueabihf
--with-sysroot=/home/builduser/x-tools/arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/sysroot
--enable-languages=c,c++
--with-float=hard
--with-pkgversion='crosstool-NG crosstool-ng-1.23.0'
--disable-sjlj-exceptions
--enable-__cxa_atexit
--disable-libmudflap
--disable-libgomp
--disable-libssp
--disable-libquadmath
--disable-libquadmath-support
--disable-libsanitizer
--disable-libmpx
--with-gmp=/home/builduser/build/.build/arm-none-linux-gnueabihf/buildtools
--with-mpfr=/home/builduser/build/.build/arm-none-linux-gnueabihf/buildtools
--with-mpc=/home/builduser/build/.build/arm-none-linux-gnueabihf/buildtools
--with-isl=/home/builduser/build/.build/arm-none-linux-gnueabihf/buildtools
--disable-lto
--with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++ -lm'
--enable-threads=posix
--enable-target-optspace
--disable-plugin
--disable-nls
--disable-multilib
--with-local-prefix=/home/builduser/x-tools/arm-none-linux-gnueabihf/arm-none-linux-gnueabihf/sysroot
--enable-long-long
Thread model: posix
gcc version 6.3.0 (crosstool-NG crosstool-ng-1.23.0)
构建一个std :: array示例可以正常工作。
修改
如果我将CT_ARCH_CPU="cortex-a9"选项包含在我的crostool-ng配置中（在g ++中导致--with-cpu=cortex-a9），则std :: current_exception示例正常工作。
所以问题是：
为什么编译器应该生成cpu变量以及cpu变量被告知工具链（在运行时-mcpu与inbuild --with-cpu）的方式正在影响编译/链接的能力的std ::函数current_exception？