Delphi应用程序的调试（六）步进式代码调试

短命女 2022-07-15 15:29 189阅读 0赞

http://www.cnblogs.com/pchmonster/archive/2012/05/30/2526853.html

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# 步进式代码调试（Stepping Through Your Code） #

步进式代码调试是最基本的调试操作之一，但仍要在此讲述。人们常常容易犯只见树木不见森林的错误。经常复习基本的知识有助于读者了解以前不知道的东西。

# 调试沟槽符号（Debugging Gutter Symbols） #

在开始讲述之前，先要说说在调试会话期间出现在Code Editor沟槽中的符号。在之前的讲解中讲过，当用户在一个代码行上设置一个断点，沟槽中就会出现一个红色的圆圈。

[![image][]][image 1]

沟槽中还有一个绿色箭头符号指示执行点所在位置。如下图：

[![image][image 2]][image_image 2]

有一点没有讲过，就是在沟槽中与某些代码行对应的位置上有一些蓝色小点。这些蓝点指示实际产生汇编代码的源代码。如下图，调试器停在一个断点处时的Code Editor。其中有指示产生汇编代码的源代码行的蓝色小点，也有指示执行点的箭头符号，还有断点符号。断点符号上的复选标志表示该断点是一个有效断点。

[![image][image 3]][image_image 3]

仔细观察上面的代码，不带小点的代码行不产生任何编译代码。例如上面的：

<table style="border:1px solid silver; width:1571px; border-collapse:collapse; word-break:break-word; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:12px!important; min-height:auto!important; background:none!important"> 
 <tbody style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
  <tr style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
   <td style="border:1px solid silver; padding:3px; border-collapse:collapse; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:35px!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; color:rgb(175,175,175)!important; background:none!important"> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important">
      1 
    </div> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important">
      2 
    </div> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important">
      3 
    </div> </td> 
   <td style="border:1px solid silver; padding:3px; border-collapse:collapse; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important"> 
    <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">var</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">S: string;</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">X: Integer;</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

为什么这几行不产生代码呢？因为它们是变量声明行。再看一行：

为什么这一行不产生代码呢？这是因为代码优化的缘故。编译器在编译代码时会发现变量X未实际使用过，从而将它优化掉。再看下面几行：

<table style="border:1px solid silver; width:1571px; border-collapse:collapse; word-break:break-word; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:12px!important; min-height:auto!important; background:none!important"> 
 <tbody style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
  <tr style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
   <td style="border:1px solid silver; padding:3px; border-collapse:collapse; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:35px!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; color:rgb(175,175,175)!important; background:none!important"> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important">
      1 
    </div> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important">
      2 
    </div> 
    <div style="border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 0.5em!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important">
      3 
    </div> </td> 
   <td style="border:1px solid silver; padding:3px; border-collapse:collapse; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important"> 
    <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">{$IFNDEF WIN32}</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">S := 'Something's very wrong here...';</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none rgb(244,244,244)!important"> 
      <code style="white-space:pre-wrap; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; min-height:auto!important; background:none!important">{$ENDIF}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

编译器不会编译器伪指令之间的源代码行进行编译，因为符号WIN32定义在一个Delphi7的程序中。编译器伪指令\{$IFNDEF WIN32\}告诉编译器：如果目标平台不是32位Windows，就编译这一行。因为Delphi7是32位编译器，所以不编译这行代码。如果是在Delphi1（16位环境）中，这行源代码就要编译。

#  #

# 步进式调试与跟踪（Step Over and Trace Into） #

好了，再回到“步进式调试代码”上来。当程序在断点处暂停时，用户可以做很多事情：在Watch List中设置要监视的变量，用Debug Inspector检查对象或查看调用栈。还可以步进式调试代码，当每一个代码行执行时，监视变量和对象的变化。

当继续步进式调试时，会看到源代码中下一步要执行的源代码以蓝色加亮显示。如下图：

[![image][image 4]][image_image 4]

如果打开了Watch List窗口和Debug Inspector窗口，它们就会随着每一代码的执行而被更新。在Watch List和Debug Inspector窗口中能立即看到变量和对象的变化。IDE调试器有两个主要步进命令：Step Over和Trace Into。

# 1、Step Over #

Step Over是指执行一行源代码，并在其下一行暂停。“Step Over”在此有点用词不当，因为从字面上理解，是跳过一个源代码行的意思。但是，此处不能从字面上去理解Step Over。实际上，Step Over是指执行当前源代码行，如果该行代码调用了函数或过程，则所调用的函数或过程也要完整地执行完。例如，一个程序的某行代码调用一个方法，在该代码行上设置一个断点；当用调试器Step Over该行代码时，调试器将执行完所调用的方法并停在下一行代码上。

要用Step Over调试程序，可以按F8键，也可以从主菜单上选【Run | Step Over】，或从工具栏中选择[![image][image 5]][image_image 5]。

> ### Note ###
> 
> 当用户步进式调试程序中的各个源代码单元时，Code Editor会自动装入并显示所需的源代码单元（如果这些单元还未打开）。

# 2、Trace Into #

当用户在步进式调试代码过程中碰到函数或过程时，Trace Into命令允许用户跟踪该函数或过程的执行。Trace Into不是像Step Over那样执行完函数或过程后返回到下一行，而是将执行点放置到所调用函数或过程的第一行源代码上，然后用户可以使用Step Over或Trace Into来逐步步进调试该函数或过程。Trace Into的快捷键为F7。

当用户检查完变量以及做完其他要做的调试工作后，可点击Run按钮再运行该程序，程序将会正常运行，直至碰到下一个断点。

> ### Note ###
> 
> 如果用户有专业版Delphi或客户/服务器版Delphi，那就可以跟踪VCL源代码。当碰到一个VCL方法时，Trace Into允许用户进入该方法的VCL源代码，用户可查看任何需要查看的变量。必须将VCL源代码所在目录的路径添加到Project Options对话框（Directories/Conditionals页面）上的Search Path字段中，如下图：
> 
> [![image][image 6]][image_image 6]
> 
> OK确认之后要重新编译、链接。跟踪VCL源代码对大多数编程人员可能意思不大；但对于经验丰富的程序员，它是非常有用的。

# 3、Trace To Next Source Line #

另外一个调试命令是“Trace To Next Source Line”快捷键是【Shift + F7】。可从主菜单选择【Run | Trace to Next Source Line】菜单项打开该命令。

[![image][image 7]][image_image 7]

用户不会频繁使用这个命令，特别是调试和Windows编程还不太熟悉的用户。有些Windows API函数使用回调函数，意思是指Windows函数调用用户的函数来执行一些操作。

如果执行点在一个Windows API函数上，而这个函数使用一个回调函数，则使用Trace to Next Source Line命令会跳过执行点到回调函数的第一行。其效果类似于Trace Into（但在某些特定情况下，两者的效果却又完全不同。）。

当步进式调试一个方法时，执行点最终要到达该方法的end语句。若所调试的方法在其运行结束后将控制权返回给Windows，则当执行点在方法的end语句时按F8键，可退出该方法并把控制返回给正调试的程序。此时不能确定程序会不会再暂停，因为IDE具有输入焦点。要切回到该程序，将其激活就可以了。（点击其在Windows任务栏上的按钮）。

步进式代码调试是一个基本的调试技术，用户在调试程序时要经常使用这一技术，因此用户要记住有关的键盘快捷键：

# 【F7】Trace Into #

# 【F8】 Step Over #

# 【F9】 Run #

分类:  [Delphi IDE][]

[image]: /images/20220715/96e724e750f84e2fb64f1775edce7f6c.png
[image 1]: http://images.cnblogs.com/cnblogs_com/pchmonster/201205/201205302036111336.png
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[Delphi IDE]: http://www.cnblogs.com/pchmonster/category/343330.html