C++ LocalAlloc() & LocalSize() & LocalFree ()

关于LocalAlloc function，参考：https://msdn.microsoft.com/en-us/library/windows/desktop/aa366723(v=vs.85).aspx

关于LocalSize function，参考：https://msdn.microsoft.com/en-us/library/windows/desktop/aa366745(v=vs.85).aspx

关于LocalFree function，参考：https://msdn.microsoft.com/en-us/library/windows/desktop/aa366730(v=vs.85).aspx

 

 

以下代码摘自：https://msdn.microsoft.com/en-us/library/windows/desktop/aa366723(v=vs.85).aspx

 

IDE: Code::Blocks 16.01

操作系统：Windows 7 x64

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

int _cdecl _tmain()
{
    LPTSTR pszBuf = NULL;

    pszBuf = (LPTSTR)LocalAlloc(
        LPTR,
        MAX_PATH * sizeof(TCHAR));

    // Handle error condition
    if (pszBuf == NULL)
    {
        _tprintf(TEXT("LocalAlloc failed (%ld)\n"), GetLastError());
        return 1;
    }

    //see how much memory was allocated
    _tprintf(TEXT("LocalAlloc allocated %d bytes\n"), LocalSize(pszBuf));

    // Use the memory allocated

    // Free the memory when finished with it
    LocalFree(pszBuf);

    return 0;
}

 

在Code::Blocks 16.01中的运行结果：

 

 

IDE: Microsoft Visual Studio Community 2017 15.5.2

操作系统：Windows 7 x64

#include "stdafx.h"

#include <windows.h>
//#include <stdio.h>    
//#include <tchar.h>

int _cdecl _tmain()
{
    LPTSTR pszBuf = NULL;

    pszBuf = (LPTSTR)LocalAlloc(
        LPTR,
        MAX_PATH * sizeof(TCHAR));

    // Handle error condition
    if (pszBuf == NULL)
    {
        _tprintf(TEXT("LocalAlloc failed (%d)\n"), GetLastError());
        return 1;
    }

    //see how much memory was allocated
    _tprintf(TEXT("LocalAlloc allocated %d bytes\n"), LocalSize(pszBuf));

    // Use the memory allocated

    // Free the memory when finished with it
    LocalFree(pszBuf);

    getchar();

    return 0;
}

 

 在Microsoft Visual Studio Community 2017 15.5.2中的运行结果：

 

---

 

造成两个IDE的运行结果不一样的原因，是因为TCHAR在两个IDE中的定义不一样。

 

在Code::Blocks 16.01中，TCHAR是这样定义的：

typedef CHAR TCHAR;

typedef char CHAR;

 

 而在Microsoft Visual Studio Community 2017 15.5.2中，则是这样的：

typedef wchar_t     TCHAR;

 

---

 

关于LPTR，在Code::Blocks 16.01中，是这样定义的：

#define LPTR 64

 

而在Microsoft Visual Studio Community 2017 15.5.2中，则这样：

#define LPTR                (LMEM_FIXED | LMEM_ZEROINIT)

#define LMEM_FIXED          0x0000

#define LMEM_ZEROINIT       0x0040

 

两者是等效的，不过Microsoft Visual Studio Community 2017 15.5.2的定义则比较清晰，一目了然。

 

关于LMEM_FIXED：Allocates fixed memory. The return value is a pointer to the memory object.

关于LMEM_ZEROINIT：Initializes memory contents to zero.