Qt 常见编译问题汇总

Date	Log
04/07/2017	Initial version: add “constant string to char *“ and “comparison between signed and unsigned integer “.
04/15/2017	add “undefined reference to `inet_addr@4’ “

本文汇总了在 Qt 5.8 中使用 C++进行开发时遇到的编译错误和警告及其解决方法，基于 C++11 标准。

constant string to char *

初始代码：

char *p = "Hello";

编译输出：

ISO C++ forbids conversion from constant string to char *.

修改代码：

char const *p = "Hello";

参考资料：

1. Why is conversion from string constant to ‘char*‘ valid in C but invalid in C++

comparison between signed and unsigned

初始代码：

for (int i = 0, max = vec.size(); i != max; ++i)

编译输出：

warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

修改代码：

for (std::size_t i = 0, max = vec.size(); i != max; ++i)

附加注释：

一般情况下，直接使用 size_t 即可。

参考资料：

1. What is wrong with my For loops? i get warnings: comparison between signed and unsigned integer expressions [-Wsign-compare]
2. A warning - comparison between signed and unsigned integer expressions

undefined reference to `inet_addr@4’

编译输出：

undefined reference to `inet_addr@4’

问题分析：

这种情况是因为没有把 ws2_32.lib 或 libws2_32.a 加入到编译依赖项中。

一般情况下，出现类似的 undefined reference to ‘…@…’都是因为只在源代码中引入了头文件，而没有在编译依赖中加入库文件。这种错误多出现在同时具有头文件，静态库，动态库的外部库的引用过程中。