Question

这是我的test.cpp：

#include <iostream.h>
class C {
public:
C();
~C();
};

int main()
{
C obj;
return 0;
}

当我使用命令g++ test.cpp编译它时，我收到以下错误消息：

    In file included from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/iostream.h:31,
                     from test.cpp:1:
    /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/backward_warning.h:32:2: warning: #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the  header for the  header for C++ includes, or  instead of the deprecated header . To disable this warning use -Wno-deprecated.
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/ccoYkiAS.o:test.cpp:(.text+0x131): undefined reference to `C::C()'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/ccoYkiAS.o:test.cpp:(.text+0x13c): undefined reference to `C::~C()'
    collect2: ld returned 1 exit status

使用gcc test.cpp进行编译会发出类似的消息，甚至更多：

    In file included from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/iostream.h:31,
                     from test.cpp:1:
    /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/backward_warning.h:32:2: warning: #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the  header for the  header for C++ includes, or  instead of the deprecated header . To disable this warning use -Wno-deprecated.
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0xd): undefined reference to `std::basic_string, std::allocator >::size() const'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x60): undefined reference to `std::basic_string, std::allocator >::operator[](unsigned int) const'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x9f): undefined reference to `std::basic_string, std::allocator >::operator[](unsigned int) const'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0xce): undefined reference to `std::basic_string, std::allocator >::operator[](unsigned int) const'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x131): undefined reference to `C::C()'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x13c): undefined reference to `C::~C()'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x165): undefined reference to `std::ios_base::Init::Init()'
    /cygdrive/c/Users/aswinik_sattaluri/AppData/Local/Temp/cc3ntGx0.o:test.cpp:(.text+0x180): undefined reference to `std::ios_base::Init::~Init()'
    collect2: ld returned 1 exit status

请注意，我尚未设置LD_LIBRARY_PATH：

    bash-3.2$ echo $LD_LIBRARY_PATH

    bash-3.2$

Answer 1

您已声明C构造函数和析构函数的存在，但尚未提供实现。尝试：

class C {
public:
    C() {}
    ~C() {}
};

而且，对于C ++程序，使用g++进行编译（如第一次尝试）。

Answer 2

替换

#include <iostream.h>

通过

#include <iostream>

并提供类C的构造函数和析构函数的实现，至少为空。

Answer 3

由于您没有提供实际问题，我不得不猜测您想知道什么。无论如何，我的2c是：

请勿使用iostream.h，该标头已预先标准且已过期。请改用<iostream>
您没有为C的构造函数和析构函数提供任何实现，这是链接器所抱怨的。

Answer 4

您需要定义C构造函数和destuctor：

C::C()
{
}

C::~C()
{
}

另外，坚持用g ++编译。如果仔细观察，使用gcc编译时遇到的错误包括g ++加上额外错误所带来的一切。

Answer 5

您包含iostream.h而不是iostream，这就是您收到此警告的原因。你还为C声明了一个构造函数和析构函数，但你实际上并没有在任何地方实现它。因此链接器抱怨未定义的符号。

您需要为C的方法添加实现，例如：

C::C() {
  // ...
}

Answer 6

使用#include <iostream>代替#include <iostream.h>

你应该正确阅读错误。

Answer 7

关于LD_LIBRARY_PATH的一个注意事项 - 它在编译或链接时并不关心你（然后链接器会查看用-L和一些标准路径给出的路径，比如/ usr / lib）。

这很重要当您运行应用程序时 - 系统将首先在LD_LIBRARY_PATH中给出的路径中搜索共享库。

http://www.linux.org/docs/ldp/howto/Program-Library-HOWTO/shared-libraries.html

编译C ++代码时出错？

7 个答案: