1.问题描述
在使用虚基类的时候，编译遇到了如下错误：
|
1 2 3 4 5 6 7 8 9 10 |
Undefined symbols for architecture x86_64: "typeinfo for HandlerBase", referenced from: typeinfo for DNSResolveHandler in test-dns-b857ca.o typeinfo for DNSResolver in asyncdns-061190.o "vtable for HandlerBase", referenced from: HandlerBase::HandlerBase() in test-dns-b857ca.o HandlerBase::HandlerBase() in asyncdns-061190.o NOTE: a missing vtable usually means the first non-inline virtual member function has no definition. ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) |
对应的代码为：
|
1 2 3 4 5 6 7 8 |
class HandlerBase{ public: virtual void handleEvent(int socketfd, UCHAR event) = 0; virtual void handlePeriodic(void) = 0; // this virtual function is used in TCPRelay class virtual void handleDNSResolved(std::string hostname, std::string ip, \ int error); }; |
2.解决方案
应该在基类中定义虚函数（不能仅仅声明）或者将虚函数声明成纯虚函数。因此，可消除编译错误的方式有两种。
其一，定义虚函数
|
1 2 3 4 5 6 7 8 |
class HandlerBase{ public: virtual void handleEvent(int socketfd, UCHAR event) = 0; virtual void handlePeriodic(void) = 0; // this virtual function is used in TCPRelay class virtual void handleDNSResolved(std::string hostname, std::string ip, \ int error) {}; }; |
其二，声明虚函数喂纯虚函数
|
1 2 3 4 5 6 7 8 |
class HandlerBase{ public: virtual void handleEvent(int socketfd, UCHAR event) = 0; virtual void handlePeriodic(void) = 0; // this virtual function is used in TCPRelay class virtual void handleDNSResolved(std::string hostname, std::string ip, \ int error) = 0; }; |
相似问题：https://stackoverflow.com/questions/8951884/undefined-reference-to-typeinfo-for-class