error: cast from ... to ... loses precision
例子
#include <iostream>
class Foo {
public:
void print() const {
std::cout << (int)(this) << "\n";
}
};
int main()
{
class Foo foo;
foo.print();
return 0;
}
技巧
在g++编译上面的例子,会报如下错误:
$ g++ foo.cc
foo.cc: In member function ‘void Foo::print() const’:
foo.cc:6:28: error: cast from ‘const Foo*’ to ‘int’ loses precision [-fpermissive]
这是一个强制类型转换的错误,你可以修改源代码为:
std::cout << (int*)(this) << "\n";
即可。
如果,你不想(或不能)去修改源程序,只是应为升级了gcc而带来了这样的错误,那么也可以使用-fpermissive
选项,将错误降低为警告:
$ g++ foo.cc -fpermissive
foo.cc: In member function ‘void Foo::print() const’:
foo.cc:6:28: warning: cast from ‘const Foo*’ to ‘int’ loses precision [-fpermissive]
详情参见gcc手册
贡献者
xmj