c/assets/notes_01_c-basic_06_xdx_index.md.DMMIRQE2.js

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import{_ as s,c as a,o as i,a6 as n}from"./chunks/framework.CZKtKhAm.js";const t="/c/assets/1.L8V3GBrc.png",l="/c/assets/2.CdvhiwcU.png",e="/c/assets/3.D74t3-Xt.png",d="/c/assets/4.DCQsqYYC.gif",p="/c/assets/5.CUjMoXNF.gif",r="/c/assets/6.BWbajkuB.gif",c="/c/assets/7.C1JnBDr7.png",o="/c/assets/8.DwN2p3bo.png",h="/c/assets/9.DdSfz-Pf.gif",k="/c/assets/10.BMocjVt7.gif",B=JSON.parse('{"title":"第一章:颇具争议的指针","description":"","frontmatter":{},"headers":[],"relativePath":"notes/01_c-basic/06_xdx/index.md","filePath":"notes/01_c-basic/06_xdx/index.md","lastUpdated":1722388783000}'),u={name:"notes/01_c-basic/06_xdx/index.md"},g=n('<blockquote><ul><li><code>指针</code> C <code></code><code></code></li><li><code></code> C <code></code> C </li></ul></blockquote><h1 id="-" tabindex="-1"> <a class="header-anchor" href="#-" aria-label="Permalink to &quot;&quot;"></a></h1><h2 id="_1-1-" tabindex="-1">1.1 <a class="header-anchor" href="#_1-1-" aria-label="Permalink to &quot;1.1 &quot;"></a></h2><ul><li> C C <code></code><code></code><code>使</code></li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p> C 使</p></div><ul><li><p>使</p><ul><li> <strong>Null Pointer Dereference</strong>NULL访</li><li> <strong>Dangling Pointers</strong></li><li> <strong></strong></li><li> <strong></strong></li></ul></li><li><p></p><ul><li> <strong></strong>使</li><li> <strong></strong></li><li> <strong>使</strong>使 C++ 使</li></ul></li></ul><div class="important custom-block github-alert"><p class="custom-block-title">IMPORTANT</p><p></p><ul><li> JavaGoRust </li><li><EFBFBD><EFBFBD>
<span class="line"><span></span></span>
<span class="line"><span># 项目名称和版本号</span></span>
<span class="line"><span>project(c-study VERSION 1.0 LANGUAGES C)</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 设置 C 标准</span></span>
<span class="line"><span>set(CMAKE_C_STANDARD 23)</span></span>
<span class="line"><span>set(CMAKE_C_STANDARD_REQUIRED True)</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 辅助函数用于递归查找所有源文件</span></span>
<span class="line"><span>function(collect_sources result dir)</span></span>
<span class="line"><span> file(GLOB_RECURSE new_sources &quot;\${dir}/*.c&quot;)</span></span>
<span class="line"><span> set(\${result} \${\${result}} \${new_sources} PARENT_SCOPE)</span></span>
<span class="line"><span>endfunction()</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 查找顶层 include 目录如果存在</span></span>
<span class="line"><span>if (EXISTS &quot;\${CMAKE_SOURCE_DIR}/include&quot;)</span></span>
<span class="line"><span> include_directories(\${CMAKE_SOURCE_DIR}/include)</span></span>
<span class="line"><span>endif ()</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 查找所有源文件</span></span>
<span class="line"><span>set(SOURCES)</span></span>
<span class="line"><span>collect_sources(SOURCES \${CMAKE_SOURCE_DIR})</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 用于存储已经处理过的可执行文件名防止重复</span></span>
<span class="line"><span>set(EXECUTABLE_NAMES)</span></span>
<span class="line"><span></span></span>
<span class="line"><span># 创建可执行文件</span></span>
<span class="line"><span>foreach (SOURCE \${SOURCES})</span></span>
<span class="line"><span> # 获取文件的相对路径</span></span>
<span class="line"><span> file(RELATIVE_PATH REL_PATH \${CMAKE_SOURCE_DIR} \${SOURCE})</span></span>
<span class="line"><span> # 将路径中的斜杠替换为下划线生成唯一的可执行文件名</span></span>
<span class="line"><span> string(REPLACE &quot;/&quot; &quot;_&quot; EXECUTABLE_NAME \${REL_PATH})</span></span>
<span class="line"><span> string(REPLACE &quot;\\\\&quot; &quot;_&quot; EXECUTABLE_NAME \${EXECUTABLE_NAME})</span></span>
<span class="line"><span> string(REPLACE &quot;.&quot; &quot;_&quot; EXECUTABLE_NAME \${EXECUTABLE_NAME})</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 处理与 CMakeLists.txt 文件同名的问题</span></span>
<span class="line"><span> if (\${EXECUTABLE_NAME} STREQUAL &quot;CMakeLists_txt&quot;)</span></span>
<span class="line"><span> set(EXECUTABLE_NAME &quot;\${EXECUTABLE_NAME}_exec&quot;)</span></span>
<span class="line"><span> endif ()</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 检查是否已经创建过同名的可执行文件</span></span>
<span class="line"><span> if (NOT EXECUTABLE_NAME IN_LIST EXECUTABLE_NAMES)</span></span>
<span class="line"><span> list(APPEND EXECUTABLE_NAMES \${EXECUTABLE_NAME})</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 创建可执行文件</span></span>
<span class="line"><span> add_executable(\${EXECUTABLE_NAME} \${SOURCE})</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 查找源文件所在的目录并添加为包含目录头文件可能在同一目录下</span></span>
<span class="line"><span> get_filename_component(DIR \${SOURCE} DIRECTORY)</span></span>
<span class="line"><span> target_include_directories(\${EXECUTABLE_NAME} PRIVATE \${DIR})</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 检查并添加子目录中的 include 目录如果存在</span></span>
<span class="line"><span> if (EXISTS &quot;\${DIR}/include&quot;)</span></span>
<span class="line"><span> target_include_directories(\${EXECUTABLE_NAME} PRIVATE \${DIR}/include)</span></span>
<span class="line"><span> endif ()</span></span>
<span class="line"><span></span></span>
<span class="line"><span> # 检查并添加 module 目录中的所有 C 文件如果存在</span></span>
<span class="line"><span> if (EXISTS &quot;\${DIR}/module&quot;)</span></span>
<span class="line"><span> file(GLOB_RECURSE MODULE_SOURCES &quot;\${DIR}/module/*.c&quot;)</span></span>
<span class="line"><span> target_sources(\${EXECUTABLE_NAME} PRIVATE \${MODULE_SOURCES})</span></span>
<span class="line"><span> endif ()</span></span>
<span class="line"><span> endif ()</span></span>
<span class="line"><span>endforeach ()</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br><span class="line-number">42</span><br><span class="line-number">43</span><br><span class="line-number">44</span><br><span class="line-number">45</span><br><span class="line-number">46</span><br><span class="line-number">47</span><br><span class="line-number">48</span><br><span class="line-number">49</span><br><span class="line-number">50</span><br><span class="line-number">51</span><br><span class="line-number">52</span><br><span class="line-number">53</span><br><span class="line-number">54</span><br><span class="line-number">55</span><br><span class="line-number">56</span><br><span class="line-number">57</span><br><span class="line-number">58</span><br><span class="line-number">59</span><br><span class="line-number">60</span><br><span class="line-number">61</span><br><span class="line-number">62</span><br><span class="line-number">63</span><br><span class="line-number">64</span><br></div></div><ul><li> CLion </li></ul><p><img src="`+h+'" alt=""></p><ul><li> CLion valgrind </li></ul><p><img src="'+k+`" alt=""></p><h1 id="--" tabindex="-1"> <a class="header-anchor" href="#--" aria-label="Permalink to &quot;&quot;"></a></h1><h2 id="_4-1-" tabindex="-1">4.1 <a class="header-anchor" href="#_4-1-" aria-label="Permalink to &quot;4.1 &quot;"></a></h2><h1 id="--" tabindex="-1"> <a class="header-anchor" href="#--" aria-label="Permalink to &quot;&quot;"></a></h1><h2 id="_5-1-" tabindex="-1">5.1 <a class="header-anchor" href="#_5-1-" aria-label="Permalink to &quot;5.1 &quot;"></a></h2><h2 id="_5-2-" tabindex="-1">5.2 <a class="header-anchor" href="#_5-2-" aria-label="Permalink to &quot;5.2 &quot;"></a></h2><ul><li><p> C <code></code><code></code><code></code></p><ul><li> <strong></strong><code>int a = 5</code></li><li> <strong></strong>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">ptr </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> arr;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // ptrarr[0]</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%p\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, arr);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // </span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%p\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&amp;</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">arr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">[</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">]);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // </span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div></li><li><p><strong></strong> </p><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;"> arr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">[</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">];</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">ptr </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> arr;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // ptrarr[0]</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">ptr</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">++</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // ptrarr[1]</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// arr++; // 非法,编译错误,因为数组名是常量,不能改变</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div></li><li><p><strong>sizeof运算符的结果不同</strong> 使用<code>sizeof</code>运算符对数组名和指针变量会得到不同的结果,数组名会返回整个数组的大小,而指针变量会返回指针本身的大小。</p><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;"> arr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">[</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">];</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">ptr </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> arr;</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;sizeof(arr) = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%lu\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">sizeof</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(arr));</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 5 * sizeof(int)</span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;sizeof(ptr) = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%lu\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">sizeof</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(ptr));</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 48</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div></li><li><p><strong></strong> 使<code>&amp;</code>使<code>&amp;</code>使<code>&amp;</code></p><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;"> arr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">[</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">];</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">ptr </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> arr;</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Address of array: </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%p\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&amp;</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">arr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // </span></span>
<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;">printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;Address of pointer: </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%p\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&amp;</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">ptr</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // ptr</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div></li></ol><p>使</p>`,72),E=[g];function b(m,C,y,F,_,A){return i(),a("div",null,E)}const q=s(u,[["render",b]]);export{B as __pageData,q as default};