sizeof与strlen的区别：面试回答

示例：

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *ptr = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello world"</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> str[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>] = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello world"</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(ptr) = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>B
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(str) = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>B
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strlen</span>(ptr) = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">11</span>B
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strlen</span>(ptr) = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">11</span>B</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="box-sizing: border-box; position: absolute; height: 60px; right: 30px; top: 5px; color: rgb(255, 255, 255); cursor: pointer; z-index: 2;"><a target=_blank target="_blank" style="color: rgb(106, 57, 6); box-sizing: border-box;"><img src="http://static.blog.youkuaiyun.com/images/save_snippets.png" style="border: none; box-sizing: border-box; max-width: 100%;" alt="" /></a></div>

面试回答总结：

我认为sizeof（）与strlen（）有以下几个区别。strlen是一个函数，它测量的是字符串中除去’\0’以外的字符数；而sizeof是一个关键字，含义可用作运算符。它测量的是对象或者类型所占的内存的字节数，包括’\0’在内；对于strlen的使用没有什么限制。而当sizeof测量指针的长度，得到的是地址的长度；当sizeof测量数组的时候，得到的是整个数组的长度；当函数调用数组做为参数的时候，用sizeof测量得到的仍然是一个指针的长度。

转载网址：http://blog.youkuaiyun.com/zxnsirius/article/details/51159191