请考虑以下代码:
#include <complex>
int main()
{
unsigned u = 1u;
auto result = static_cast<std::complex<int>>(u);
return 0;
}
编译使用
g++ -std=c++11 -Werror -Wsign-conversion -o a.out source_file.cpp
导致编译错误
source_file.cpp: In function ‘int main()’:
source_file.cpp:8:51: error: conversion to ‘int’ from ‘unsigned int’ may change the sign of the result [-Werror=sign-conversion]
auto result = static_cast<std::complex<int>>(u);
^
Clang 报告类似的错误
source_file.cpp:6:50: error: implicit conversion changes signedness: 'unsigned int' to 'const value_type' (aka 'const int') [-Werror,-Wsign-conversion]
auto result = static_cast<std::complex<int>>(u);
~~~~~~~~~~~ ^
乍一看错误没有多大意义,我错过了什么?
您收到的转换警告不是来自演员表,而是来自std::complex
的内部构造。
要"修复"您的示例,您应该改为:
auto result = std::complex<int>{static_cast<int>(u)};