警告C4018：'<' ：有符号/无符号不匹配 [英] warning C4018: '<' : signed/unsigned mismatch

问题描述

在将项目从vc ++ 6.0迁移到vs 2008时，我收到以下警告。任何人都可以向我解释为什么会出现此警告？

On migrating a project from vc++ 6.0 to vs 2008, I get the below warnings. Can anyone please explain me why this warning occurs?

inline tstring& tstring::trim()
{
    long lDelFront = 0, lDelBack = 0;

    while (lDelFront < length() && at(lDelFront) == ' ')      //C4018 Warning
        lDelFront++;

    if ( lDelFront > 0 )
    {
        erase(0, lDelFront);
    }

    while (lDelBack < length() &&                       //C4018 Warning
            at(length() - lDelBack - 1) == ' ')
        lDelBack++;

    if ( lDelBack > 0 )
    {
        erase(length() - lDelBack, lDelBack);
    }

    return *this;
}

谢谢！
Ankush

Thanks! Ankush

推荐答案

length（）可能返回size_t或unsigned long，
更改

length() probably returns size_t or unsigned long and you are comparing it with signed long. Change

long lDelFront = 0, lDelBack = 0;

到

size_t lDelFront = 0;
size_t lDelBack = 0;

以避免签名/无符号比较

to avoid signed/unsigned comparison

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