G++简单程序的编译错误

Question

在尝试学习一些 C 之后，我尝试了一些 C++ 编程，以直观地了解语言之间的一些差异。当尝试编译程序时，我在库中遇到很多错误
代码：

#include <iostream>
using namespace std;

int main() 
{
    cout << "Hello, World!\n";
    return 0;
}

和错误：

In file included from /usr/include/c++/9/cstdio:42,
                 from /usr/include/c++/9/ext/string_conversions.h:43,
                 from /usr/include/c++/9/bits/basic_string.h:6493,
                 from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from new.cpp:1:
/usr/lib/gcc/x86_64-linux-gnu/9/include/stdio.h:46:25: error: conflicting declaration ‘typedef struct __sFILE FILE’
   46 |  typedef struct __sFILE FILE;
      |                         ^~~~
In file included from /usr/include/wchar.h:46,
                 from /usr/include/c++/9/cwchar:44,
                 from /usr/include/c++/9/bits/postypes.h:40,
                 from /usr/include/c++/9/iosfwd:40,
                 from /usr/include/c++/9/ios:38,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from new.cpp:1:
/usr/include/x86_64-linux-gnu/bits/types/FILE.h:7:25: note: previous declaration as ‘typedef struct _IO_FILE FILE’
    7 | typedef struct _IO_FILE FILE;
      |                         ^~~~
In file included from /usr/include/c++/9/ext/string_conversions.h:43,
                 from /usr/include/c++/9/bits/basic_string.h:6493,
                 from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from new.cpp:1:
/usr/include/c++/9/cstdio:99:11: error: ‘::fpos_t’ has not been declared
   99 |   using ::fpos_t;
      |           ^~~~~~
/usr/include/c++/9/cstdio:101:11: error: ‘::clearerr’ has not been declared
  101 |   using ::clearerr;
      |           ^~~~~~~~
/usr/include/c++/9/cstdio:102:11: error: ‘::fclose’ has not been declared
  102 |   using ::fclose;
      |           ^~~~~~
/usr/include/c++/9/cstdio:103:11: error: ‘::feof’ has not been declared
  103 |   using ::feof;
      |           ^~~~
/usr/include/c++/9/cstdio:104:11: error: ‘::ferror’ has not been declared
  104 |   using ::ferror;
      |           ^~~~~~
/usr/include/c++/9/cstdio:105:11: error: ‘::fflush’ has not been declared
  105 |   using ::fflush;
      |           ^~~~~~
/usr/include/c++/9/cstdio:107:11: error: ‘::fgetpos’ has not been declared
  107 |   using ::fgetpos;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:109:11: error: ‘::fopen’ has not been declared
  109 |   using ::fopen;
      |           ^~~~~
/usr/include/c++/9/cstdio:110:11: error: ‘::fprintf’ has not been declared
  110 |   using ::fprintf;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:114:11: error: ‘::freopen’ has not been declared
  114 |   using ::freopen;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:115:11: error: ‘::fscanf’ has not been declared
  115 |   using ::fscanf;
      |           ^~~~~~
/usr/include/c++/9/cstdio:116:11: error: ‘::fseek’ has not been declared
  116 |   using ::fseek;
      |           ^~~~~
/usr/include/c++/9/cstdio:117:11: error: ‘::fsetpos’ has not been declared
  117 |   using ::fsetpos;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:118:11: error: ‘::ftell’ has not been declared
  118 |   using ::ftell;
      |           ^~~~~
/usr/include/c++/9/cstdio:126:11: error: ‘::perror’ has not been declared
  126 |   using ::perror;
      |           ^~~~~~
/usr/include/c++/9/cstdio:131:11: error: ‘::remove’ has not been declared
  131 |   using ::remove;
      |           ^~~~~~
/usr/include/c++/9/cstdio:132:11: error: ‘::rename’ has not been declared
  132 |   using ::rename;
      |           ^~~~~~
/usr/include/c++/9/cstdio:133:11: error: ‘::rewind’ has not been declared
  133 |   using ::rewind;
      |           ^~~~~~
/usr/include/c++/9/cstdio:135:11: error: ‘::setbuf’ has not been declared
  135 |   using ::setbuf;
      |           ^~~~~~
/usr/include/c++/9/cstdio:136:11: error: ‘::setvbuf’ has not been declared
  136 |   using ::setvbuf;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:139:11: error: ‘::tmpfile’ has not been declared
  139 |   using ::tmpfile;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:141:11: error: ‘::tmpnam’ has not been declared
  141 |   using ::tmpnam;
      |           ^~~~~~
/usr/include/c++/9/cstdio:176:11: error: ‘::vfscanf’ has not been declared
  176 |   using ::vfscanf;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:177:11: error: ‘::vscanf’ has not been declared
  177 |   using ::vscanf;
      |           ^~~~~~
/usr/include/c++/9/cstdio:179:11: error: ‘::vsscanf’ has not been declared
  179 |   using ::vsscanf;
      |           ^~~~~~~
/usr/include/c++/9/cstdio:186:22: error: ‘__gnu_cxx::vfscanf’ has not been declared
  186 |   using ::__gnu_cxx::vfscanf;
      |                      ^~~~~~~
/usr/include/c++/9/cstdio:187:22: error: ‘__gnu_cxx::vscanf’ has not been declared
  187 |   using ::__gnu_cxx::vscanf;
      |                      ^~~~~~
/usr/include/c++/9/cstdio:189:22: error: ‘__gnu_cxx::vsscanf’ has not been declared
  189 |   using ::__gnu_cxx::vsscanf;
      |                      ^~~~~~~

g++ -v 命令结果：

Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/9/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 9.3.0-17ubuntu1~20.04' --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,gm2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-9 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-9-HskZEa/gcc-9-9.3.0/debian/tmp-nvptx/usr,hsa --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) 

注意：
我尝试重新安装 g++，因为我认为某些库已损坏，但它不起作用。 另外，我使用 Ubuntu 20.04 LTS，如果这有用的话

Answer 1

系统标头 /usr/lib/gcc/x86_64-linux-gnu/9/include/stdio.h 中有重复的符号。但根据 Ubuntu manifest，您的 GCC 版本确实<强>不包含此文件，也许它已经从不同的版本中过时了？

我的建议是删除这个文件，或者删除（或者移走，以防万一）整个文件夹（那里可能还有其他过时的文件）并重新安装 libgcc-9-dev 包。

如果您想在删除文件之前确定，可以使用以下命令检查它是否属于任何包：

$ dpkg -S /usr/lib/gcc/x86_64-linux-gnu/9/include/stdio.h