Question

即使代码正确，我的 Visual Studio 编译器也会向我显示错误消息。

即使是像这样的简单代码，

 #include<stdio.h>

int main(){
    int add(firstNumber, secondNumber){
        int result=firstNumber+secondNumber;
        return result;
    }
    int out=add(10,30);
    printf("%d", out);
    return 0;
}

它正在显示按摩，

<块引用>

应为“;”，第 4 行

和

<块引用>

标识符“out”未定义，第 9 行

代码运行良好。但是在我的代码中看到那些红线和错误消息令人沮丧。

注意：我使用 MinGW 作为 C 路径

Answer 1

C 和 C++ 标准都不允许在这个程序中定义嵌套函数

function Set-DoubleBuffered{
<#
.SYNOPSIS
Turns on double buffering for a [System.Windows.Forms.Control] object
.DESCRIPTION
Uses the Non-Public method 'SetStyle' on the control to set the three
style flags recomend for double buffering: 
   UserPaint
   AllPaintingInWmPaint
   DoubleBuffer
.INPUTS
[System.Windows.Forms.Control]
.OUTPUTS
None
.COMPONENT  
System.Windows.Forms.Control
.FUNCTIONALITY
Set Flag, DoubleBuffering, Graphics
.ROLE
WinForms Developer
.NOTES
Throws an exception when trying to double buffer a control on a terminal 
server session becuase doing so will cause lots of data to be sent across 
the line
.EXAMPLE
#A simple WinForm that uses double buffering to reduce flicker
Add-Type -AssemblyName System.Windows.Forms
[System.Windows.Forms.Application]::EnableVisualStyles()

$Pen = [System.Drawing.Pen]::new([System.Drawing.Color]::FromArgb(0xff000000),3)

$Form = New-Object System.Windows.Forms.Form
Set-DoubleBuffered $Form
$Form.Add_Paint({
   param(
      [object]$sender,
      [System.Windows.Forms.PaintEventArgs]$e
   )
   [System.Windows.Forms.Form]$f = $sender
   $g = $e.Graphics
   $g.SmoothingMode = 'AntiAlias'
   $g.DrawLine($Pen,0,0,$f.Width/2,$f.Height/2)
})
$Form.ShowDialog()

.LINK
https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.control.setstyle?view=net-5.0
.LINK
https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.controlstyles?view=net-5.0
#>
   param(
      [parameter(mandatory=$true,ValueFromPipeline=$true)]
      [ValidateScript({$_ -is [System.Windows.Forms.Control]})]
      #The WinForms control to set to double buffered
      $Control,
      
      [switch]
      #Override double buffering on a terminal server session(not recomended)
      $Force
   )
   begin{try{
      if([System.Windows.Forms.SystemInformation]::TerminalServerSession -and !$Force){
         throw 'Double buffering not set on terminal server session.'
      }
      
      $SetStyle = ([System.Windows.Forms.Control]).GetMethod('SetStyle',
         [System.Reflection.BindingFlags]::NonPublic -bor [System.Reflection.BindingFlags]::Instance
      )
      $UpdateStyles = ([System.Windows.Forms.Control]).GetMethod('UpdateStyles',
         [System.Reflection.BindingFlags]::NonPublic -bor [System.Reflection.BindingFlags]::Instance
      )
   }catch {$PSCmdlet.ThrowTerminatingError($PSItem)}
   }process{try{
      $SetStyle.Invoke($Control,@(
         ([System.Windows.Forms.ControlStyles]::UserPaint -bor
           [System.Windows.Forms.ControlStyles]::AllPaintingInWmPaint -bor
           [System.Windows.Forms.ControlStyles]::DoubleBuffer
         ),
         $true
      ))
      $UpdateStyles.Invoke($Control,@())
   }catch {$PSCmdlet.ThrowTerminatingError($PSItem)}}
}

其中函数 #include<stdio.h> int main(){ int add(firstNumber, secondNumber){ int result=firstNumber+secondNumber; return result; } int out=add(10,30); printf("%d", out); return 0; } 在函数 add 中定义。

此外，参数列表中的标识符 main 和 firstNumber 没有类型说明符。

您必须将函数定义移到 main 之外。例如

secondNumber

在 C++ 中，您可以使用 lambda 表达式而不是函数 #include<stdio.h> int add( int firstNumber, int secondNumber ) { int result = firstNumber + secondNumber; return result; } int main( void ){ int out=add(10,30); printf("%d", out); return 0; }。例如

add

Answer 2

问题是你在 main 中定义的函数，C 不支持在其他函数中定义的函数。您的代码应如下所示。

#include <stdio.h>
    

int add(firstNumber, secondNumber){
    int result=firstNumber+secondNumber;
    return result;
}

int main(){
    int out=add(10,30);
    printf("%d", out);
    return 0;
}

即使代码正确，Visual Studio C/C++ 扩展也会显示错误消息

2 个答案: